Why is the hot water riser rounded: the truth about water hammer and plastic pipes. Water hammer in water supply and heating systems Water hammer compensators for pipelines

(VT.CAR19.I) Diaphragm hydraulic shock absorber VT.CAR 19 is designed to compensate for pressure surges that occur during sudden opening or closing shut-off valves in apartment water supply systems. The device also plays the role of an expansion tank, receiving excess water volume that occurs in the pipes during natural heating in the absence of water intake. The VT.CAR 19 water hammer compensator is a miniature tank made of AISI 304L stainless steel with an internal dividing membrane made of EPDM elastomer. Small convexities on the surface of the membrane ensure its loose connection to the body and maximum contact area of the membrane with the transported medium. The capacity of the water hammer absorber VT.CAR 19 is 0.162 l, the factory setting of the pressure in the air chamber is 3.5 bar, the maximum operating pressure in the protected apartment water supply is 10 bar, the maximum pressure during water hammer is 20 bar, the maximum operating temperature is 100 ° C . The diameter of the connecting thread is 1/2". Dimensions (height x diameter) of the product are 112 x 88, mm. The factory setting provides protection for pipelines with a nominal operating pressure of 3 bar. When using the compensator in systems with other parameters, the tank should be reconfigured so that the pressure in the air chamber exceeded the nominal pressure by 0.5 bar.

General information about water hammer

Water hammer is an abrupt change in the pressure of a fluid flowing in a pressure pipeline that occurs when there is a sudden change in flow speed. In a more comprehensive sense, water hammer is a fleeting alternation of “jumps” and “dips” in pressure, accompanied by deformation of the liquid and pipe walls, as well as an acoustic effect similar to hitting a hammer with a hammer. steel pipe. With weak hydraulic shocks, the sound appears in the form of “metallic” clicks, but even with such seemingly insignificant shocks, the pressure in the pipeline can increase quite significantly.

The stages of water hammer can be illustrated with the following example ( Fig.1): let a single-lever faucet or mixer be installed at the end of the apartment pipeline connected to the house riser (it is precisely these mixers that allow you to shut off the flow relatively quickly).

Fig.1. Stages of water hammer

When the tap is turned off, the following processes occur:

While the tap is open, the liquid moves through the apartment pipeline at a speed of " ν " At the same time, the pressure in the riser and the apartment pipeline is the same ( p).
When the tap is closed and the flow is suddenly slowed down, the kinetic energy of the flow is converted into work of deformation of the pipe walls and liquid. The walls of the pipe are stretched and the liquid is compressed, which leads to an increase in pressure by Δp(shock pressure). The zone in which the pressure increased is called the compression zone by the shock wave, and its extreme section is called the shock wave front. The shock wave front propagates towards the riser at a speed of “c”. Here I would like to note that the assumption of water incompressibility, adopted in hydraulic calculations, in in this case does not apply, because real water is a compressible liquid with a volumetric compression ratio of 4.9x10 -10 1/Pa. That is, at a pressure of 20,400 bar (2040 MPa), the volume of water is halved.
When the front of the shock wave reaches the riser, all the liquid in the apartment pipeline will be compressed, and the walls of the apartment pipeline will be stretched.
The volume of liquid in the house system is much larger than in the apartment wiring, therefore, when the front of the shock wave reaches the riser, the excess liquid pressure is mostly smoothed out due to the expansion of the cross-section and the inclusion of the total volume of liquid in the house system. The pressure in the apartment pipeline begins to equalize with the riser pressure. But at the same time, the apartment pipeline, due to the elasticity of the wall material, restores its original cross-section, compressing the liquid and squeezing it into the riser. The zone of deformation removal from the walls of the pipeline extends towards the tap at a speed of " With».
At the moment when the pressure in the apartment pipeline is equal to the initial one, as well as the fluid speed, the flow direction will be reversed (“zero point”).
Now the liquid in the pipeline at a speed of " ν "Tends to "break away" from the tap. A “shock wave rarefaction zone” appears. In this zone, the flow velocity is zero, and the liquid pressure becomes lower than the initial one, which leads to compression of the pipe walls (reduction in diameter). The front of the vacuum zone moves towards the riser at a speed of " With" At a significant initial flow rate, vacuum in the pipe can lead to a decrease in pressure below atmospheric pressure, as well as to a violation of the continuity of the flow (cavitation). In this case, a cavitation bubble appears in the pipeline near the tap, the collapse of which leads to the fact that the liquid pressure in the zone of the reflected shock wave becomes greater than the same indicator in the direct shock wave.
When the compression front of the shock wave of the riser is reached, the flow velocity in the apartment pipeline is zero, and the liquid pressure is lower than the initial one and lower than the pressure in the riser. The walls of the pipeline are compressed.
The pressure difference between the liquid in the riser and the apartment pipeline causes liquid to flow into the apartment pipeline and equalize the pressures to the original value. In this regard, the walls of the pipe also begin to take on their original shape. This is how a reflected shock wave is formed, and the cycles are repeated again until complete extinction. In this case, the period of time during which all stages and cycles of water hammer occur does not, as a rule, exceed 0.001–0.06 s. The number of cycles may vary and depends on the characteristics of the system.

On rice. 2 The stages of water hammer are shown graphically.

Rice. 2. Graphs of pressure changes during water hammer.

Schedule for rice. 2a shows the development of hydraulic shock when the fluid pressure in the discharge zone of the shock wave does not fall below atmospheric pressure (line 0).

Schedule for rice. 2b displays a shock wave, the vacuum zone of which is below atmospheric pressure, but the hydraulic continuity of the medium is not violated. In this case, the liquid pressure in the vacuum zone is lower than atmospheric pressure, but the cavitation effect is not observed.

Schedule for Fig.2c represents the case when the hydraulic continuity of the flow is disrupted, that is, a cavitation zone is formed, the subsequent collapse of which leads to an increase in pressure in the reflected shock wave.

Types of hydraulic shocks and basic design provisions

Depending on the speed with which the shut-off valve on the pipeline closes, the water hammer can be “direct” or indirect.” “Direct” is an impact in which the flow is blocked in a time shorter than the impact period, that is, the condition is met:

T 3 ≤ 2L/s,

Where T 3– time of closure of the shut-off organ, s; L– pipeline length from locking device to the point at which constant pressure is maintained (in an apartment - to the riser), m; With– shock wave speed, m/s.

IN otherwise water hammer is called indirect. With an indirect impact, the pressure surge is much smaller in magnitude, since part of the flow energy is damped by partial leakage through the shut-off element.

Depending on the degree of blockage of the flow, the water hammer can be complete or incomplete. A complete blow is one in which the shut-off organ completely blocks the flow. If this does not happen, that is, part of the flow continues to flow through the shut-off valve, then the water hammer will be incomplete. In this case, the calculated speed for determining the magnitude of the hydraulic shock will be the difference in flow rates before and after the blocking. The magnitude of the pressure increase during direct full hydraulic shock can be determined by the formula N.E. Zhukovsky (in Western technical literature the formula is attributed to Alievi and Michaud):

Δp = ρ ν c, Pa,

Where ρ – density of the transported liquid, kg/m3; ν – speed of the transported liquid before the moment of sudden braking, m/s; With– shock wave propagation speed, m/s.

In turn, the speed of propagation of the shock wave c is determined by the formula:

Where c 0- speed of sound propagation in a liquid (for water – 1425 m/s, for other liquids it can be taken according to table 1); D– pipeline diameter, m; δ – pipe wall thickness, m; E– volumetric modulus of elasticity of the liquid (can be taken according to table 2), Pa; Eating– modulus of elasticity of the pipe wall material, Pa (can be taken according to table 3).

Table 1. Liquid characteristics

Table 2. Characteristics of pipe wall materials

If we take into account that the speed of water movement in apartment systems should not exceed 3 m/s (clause 7.6. SNiP 2.04.01), then for pipelines from various materials it is possible to calculate the magnitude of the pressure increase with a possible direct full water hammer. Such summary data for some pipes is presented in table 3.

Table 3. Increase in pressure during water hammer at a flow speed of 3 m/s

Pipe material and dimensions	Shock wave speed, m/s	Δр, bar
Metal polymer






Polyethylene







Polypropylene



















Steel (VGP normal pipes)

With indirect water hammer, the pressure increase is calculated using the formula:

IN table 4 The average response time of the main apartment fittings is given. For each type of this fitting, the length of the pipeline is calculated, beyond which the water hammer ceases to be direct.

Table 4. Length of the direct impact section for water shut-off valves

Type of apartment fittings	Response time, s	Length of direct impact section, m
Type of apartment fittings	Response time, s	For non-metallic pipeline	For metal pipeline
Lever tap or mixer
Shower switch (diverter)
Washing machine solenoid valve
Dishwasher solenoid valve
Leakage protection solenoid valve (1/2")
Toilet fill valve

Possible consequences of water hammer

In residential networks, the occurrence of water hammer, of course, does not entail such large-scale destructive consequences as on large-diameter main pipelines. However, even here they can cause a lot of trouble and losses if you do not take into account the possibility of their occurrence.

Periodically repeated hydraulic shocks in residential piping can cause the following troubles:

– reduction of pipeline service life. The standard service life of internal pipelines is determined by the set of characteristics (temperature, pressure, time) in which the pipe is operated. Even such short-term, but often repeated, alternating pressure surges and dips that occur during a hydraulic shock significantly distort the picture of the pipeline’s operating conditions, reducing the period of its trouble-free operation. This applies to a greater extent to polymer and multilayer pipelines;

– squeezing out gaskets and seals in fittings and pipeline connectors. Elements such as piston pressure reducers, ball valves, valves and mixers with rubber gland rings, sealing rings of crimp and press connectors, as well as half-fitting rings (“American women”) are susceptible to this. In apartment water meters, squeezing out the sealing ring between the measuring chamber and the counting mechanism can lead to water entering the counting mechanism (Fig. 3);

Rice. 3. Water entering the water meter counting mechanism as a result of squeezing out the gasket

– even a single water hammer can completely disable the control and measuring instruments installed in the apartment. For example, the bending of the pressure gauge needle due to interaction with the limiting pin is a clear sign of a water hammer that has taken place (Fig. 4);

Rice. 4. Typical damage to the pressure gauge due to hydraulic shock

– each water hammer in the apartment pipeline from polymer materials, made on crimp, press or push-in connectors, inevitably leads to microscopic “slipping” of the connector from the pipeline. In the end, a moment may come when the next water hammer becomes critical - the pipe completely “crawls out” of the connector (Fig. 5);

Rice. 5. Failure of the MPT crimp connection as a result of water hammer

– cavitation phenomena, which can accompany water hammer, are often the cause of the appearance of cavities in the spool and valve body. The collapse of vacuum bubbles during cavitation simply “gnaws out” pieces of metal from the surface on which they form. As a result, the spool ceases to perform its function, that is, the tightness of the shut-off organ is broken. And the body of such fittings will very quickly fail (Fig. 6);

Rice. 6. Cavitation destruction of the internal surface of the discharge in front of the solenoid valve

– a particular danger for residential pipelines made of multilayer pipes is the zone of discharge of the shock wave during a hydraulic shock. If the adhesive layer is of poor quality or there are unglued areas, the vacuum formed in the pipe tears off the inner layer of the pipe, causing it to “collapse” (Fig. 7, 8).

Rice. 7. Multilayer polypropylene pipe, damaged by water hammer

Rice. 8. “Collapsed” metal-polymer pipe

When partially collapsed, the pipe will continue to perform its function, but with much greater hydraulic resistance. However, complete collapse can also occur - in this case, the pipe will be blocked by its own inner layer. Unfortunately, GOST 53630-2009 “Multilayer pressure pipes” does not require testing of pipe samples at internal pressure below atmospheric pressure. However, a number of manufacturers, aware of this problem, include technical specifications a mandatory point about checking the pipe under vacuum. In particular, each roll of VALTEC multilayer pipes is connected to a vacuum pump, which brings the absolute pressure in the pipe to 0.2 atm (–0.8 bar gauge). Then, using a compressor, a polystyrene foam ball with a diameter slightly smaller than the design internal diameter of the pipe is driven through the pipe. Rolls through which the ball could not pass are mercilessly rejected and destroyed;

– another danger lies in the presence of internal hot water pipelines due to water hammer. As is known, the boiling point of water is closely dependent on pressure ( table 5).

Table 5. Dependence of boiling temperature of water on pressure

If, for example, hot water with a temperature of 70 ° C enters the apartment pipeline, and in the rarefaction zone of the water hammer the pressure decreases to an absolute value of 0.3 atm, then in this zone the water will turn into steam. Considering that the volume of steam under normal conditions is almost 1200 times greater than the volume of the same mass of water, it should be expected that this phenomenon can lead to an even greater increase in pressure in the compression zone of the shock wave.

Methods of protection against water hammer in apartment systems

The most effective and reliable way to protect against water hammer is to increase the time the shut-off valve shuts off the flow. This method is used on main pipelines. Smooth closing of the valve does not cause any destructive disturbances in the flow and eliminates the need to install bulky and expensive damping devices. In apartment systems, this method is not always acceptable, because “one-armed” lever mixers, solenoid valves for household appliances, and other fittings capable of shutting off the flow in a short period of time have become firmly established in our everyday life. In this regard, apartment engineering systems Already at the project stage, they must be designed taking into account the risk of water hammer. Constructive measures, such as the use of elastic inserts, expansion loops and expanders, are not widely used. The most popular at present are fittings specially designed for this purpose - pneumatic (piston, Fig. 9a, and membrane, Fig. 9b) or spring (Fig. 9c) water hammer absorbers.

Rice. 9. Types of water hammer absorbers

In pneumatic dampers, the kinetic energy of the liquid flow is extinguished by the energy of air compression, the pressure of which varies adiabatically with an index of K = 1.4. The volume of the air chamber of the pneumatic damper is determined from the expression:

where P 0 is the initial pressure in the air chamber, P K is the final (ultimate) pressure in the air chamber. In the above formula, the left side is an expression for the kinetic energy of the fluid flow, and the right side is the energy of air compression.

The spring parameters for spring compensators are found from the expression:

where D pr is the average diameter of the spring, I is the number of turns of the spring, G is the shear modulus, F to is the final force acting on the spring, F 0 – initial force, acting on the spring.

Among designers and installers, there is an opinion that check valves and pressure reducers also have the ability to absorb water hammer.

Check valves, indeed, cutting off part of the pipeline at the moment of sudden blocking of the flow, reduce the estimated length of the pipeline, turning a direct blow into an indirect blow of less energy. However, closing sharply under the influence of the compression stage of the shock wave, the valve itself turns into the cause of water hammer in the pipeline located before it. During the vacuum stage, the valve opens again, and, depending on the ratio of the lengths of the pipes before and after the valve, a moment may come when the shock waves of the two sections add up, increasing the pressure surge. Piston pressure reducers cannot serve as hydraulic shock absorbers due to their high inertia - due to the work of friction forces in the piston seals, they simply do not have time to react to an instantaneous change in pressure. In addition, such gearboxes themselves need protection from water hammer, which causes the sealing rings to be squeezed out of the piston seats.

Diaphragm pressure reducers have the ability to partially absorb the energy of water hammer, but they are designed for completely different force effects, so work to dampen frequent water hammer will quickly put them out of action. In addition, a sharp shutdown of the gearbox during a shock wave leads, as in the case of a check valve, to the appearance of a shock wave in the area upstream of the gearbox that is not protected by a membrane.

Among other things, apartment water hammer dampers, in addition to performing their main task, perform several more functions that are important for the safe operation of apartment pipelines. These functions will be discussed using the example of the VALTEC VT.CAR19 membrane hydraulic shock absorber (Fig. 10).

Water hammer damper VT.CAR19

Rice. 10. Water hammer damper VALTEC VT.CAR19

The residential water hammer damper VALTEC VT.CAR19 structurally consists (Fig. 11) of a spherical body made of AISI 304L stainless steel ( 1 ), with a rolled EPDM membrane ( 2 ). Thanks to small convexities on the surface of the membrane, its loose connection to the body and the maximum contact area of the membrane with the transported medium are ensured. The air chamber of the damper is at a factory pressure of 3.5 bar, which provides protection for residential pipelines whose pressure does not exceed 3 bar. The damper can also protect pipelines with a working pressure of up to 10 bar, but in this case it is necessary to use a pump connected to the nipple ( 3 ) increase the pressure in the air chamber to 10.5 bar. In cases where the operating pressure in the residential network is below 3 bar, it is recommended through the nipple ( 3 ) release some of the air from the chamber to the value Prab + 0.5 bar.

Fig. 11. Design of the VALTEC VT.CAR19 damper

Technical characteristics and overall dimensions of the damper are given in table 6.

Table 6. Technical characteristics of VALTEC VT.CAR19

Characteristic name		Meaning
Working volume
Factory value of pre-pressure in the air chamber
Maximum pressure at water hammer

Maximum operating pressure in the protected residential pipeline
Working environment temperature range

Dimensions (see sketch):
H – height
O – diameter
G – connecting thread
Material:
	Stainless steel AISI 304L
Membrane

The damper is capable of protecting pipelines from water hammer, the pressure at which increases to 20 bar, therefore, before installing the damper, it is necessary to check the magnitude of the water hammer that can occur in a particular residential pipeline. Calculation of the possible pressure during water hammer Рг can be calculated using the formula:

, bar

Ewater/Eat ratio for pipelines from different materials accepted according to table 2.

Reliably protecting apartment pipelines from water hammer, the VT.CAR19 damper, due to its design features, is capable of absorbing excess water formed when heating the incoming water. cold water during a break in water use. For example, if water with a temperature of +5°C was supplied to an apartment equipped at the inlet with a reducer or check valve, and overnight it heated up to 25°C (usual air temperature in the bathroom), then the pressure in the cut-off section of the pipeline will increase by:

ΔP = β t Δt/β v = 0.00015 · (25 – 5) / 4.9 · 10 –9 = 61.2 bar.

In the given formula β t is the coefficient of thermal expansion of water, and β v is the coefficient of volumetric compression of water (the reciprocal of the elastic modulus). The formula does not take into account the thermal expansion of the material of the pipe itself, but practice shows that every degree of increase in the temperature of the water in the pipeline increases the pressure from 2 to 2.5 bar.

This is where the second function of the membrane water hammer damper is required. By absorbing some of the water from the heating pipeline, it will relieve it of excessive load and help avoid an emergency. IN table 7 The maximum lengths of pipelines protected by the VT.CAR19 damper from thermal expansion of the liquid are given.

Table 7. Limit length of pipelines protected from thermal expansion (at ΔТ = 20°C)

As for residential hot water supply pipelines, here too the VT.CAR19 damper performs the important task of preventing water from boiling in the shock wave discharge zone. By absorbing the energy of hydraulic shock, the damper eliminates this danger.

The greatest efficiency of the water hammer absorber is achieved when it is installed directly in front of the protected fittings. In this case, the possibility of water hammer occurring is completely eliminated (Fig. 12).

Rice. 12. Installation of dampers directly in front of the protected devices

In apartment systems where pipelines do not have a significant length, it is allowed to install one damper per group of devices. In this case, it should be checked that the total length of the pipeline sections protected by one damper does not exceed the values set out in table 8.

Table 8. Length of pipeline sections protected by one damper

If the values indicated in the table are exceeded, it is necessary to install not one, but several dampers. In the case where the design pressure during water hammer exceeds the maximum permissible pressure for a given damper (20 bar for VT.CAR19), another type of device with higher strength characteristics should be selected.

In accordance with clause 7.1.4. SP 30.13330.2012 “Internal water supply and sewerage of buildings”, the provisions of which came into force on January 1, 2013, the design of water supply and shut-off valves must ensure smooth opening and closing of the water flow. But this requirement is unlikely to be met, because trade offers residents a huge range of fittings and appliances in which smooth regulation impossible. Taking this into account, leading design and construction organizations in our country are already providing for the installation of residential water hammer absorbers in their projects. For example, DSK-1 in the city of Moscow is restructuring production to implement residential water supply input units according to the diagram shown in Fig. 13.

Rice. 13. Apartment water supply inlet unit

Water hammer is a sudden surge in pressure in a pipeline, which is caused by a rapid change in the speed of water flow. Positive water hammer occurs due to a sharp closing of the valve, and negative water hammer occurs due to a sharp opening. Positive water hammer is very undesirable for heating and water supply systems.

The consequences may be cracks in pipes, failure of the pump, heat exchanger, water meter, pressure gauge and other equipment operating under pressure, and of course, cessation of water and heat supply to the house, flooding of neighbors in the apartment from the lower floors. The most unpleasant thing is a pipeline rupture. Constant exposure to shocks can lead to depressurization of even a new water supply system.

Causes of water hammer

Abrupt closing/opening of shut-off valves
Presence of air in the pipes (it is necessary to bleed air from the system)
Interruptions in operation or failure of the pump
Errors during system installation

In a modern system, instead of threaded valves, which provide for a smooth shutoff of the water flow, they are more often used Ball Valves, which abruptly shut down the system. They are convenient and reliable to use, but the number of water hammers increases with their use in the system.

If the water supply system is not installed correctly, water hammer can also occur with the use of valves. The main reason - sharp transitions in pipe diameter. When a liquid moves under pressure through a large diameter pipe and reaches a place where the pipe “narrows”, this can also cause problems, since any obstacle in the path of the liquid moving at speed changes its volume and, accordingly, the pressure. This also applies to sharp turns and pipeline bends. Pipelines with a pipe diameter of up to 100 mm and distribution over long distances are least protected from such an impact.

Water hammer also occurs due to the formation of air voids, especially at a pipe bend.

The figure below clearly shows what happens to the pipe when the tap is abruptly closed - water hammer:

Ways to prevent water hammer

There are different ways to protect the water supply system of a house or apartment:

First, it is necessary to inspect the entire system for leaks and general suitability for use, and the degree of wear of the pipes. It is better to replace old pipes with new ones. The reliability of the system depends on the quality of materials and correct installation.
Installation of valve-type shut-off valves. Smoothly close the tap so that the pressure in the water supply system smoothly equalizes.
Using larger diameter pipes . Choose a pipe diameter greater than 100 mm. The larger the diameter of the pipes, the lower the water flow rate and, accordingly, the water hammer.
Avoid long sections of pipe laying and without sharp bends, then air pockets will not form in them.
Avoid sudden temperature changes in the water pipe. When designing a house, it is necessary to take into account that the pipes go to those places and rooms where the temperature difference will be minimal. Insulate pipes.
Perform preventive maintenance on a regular basis:

Check the operation of the safety group: pressure gauge, air vent, safety valve.
Regularly check the condition of the filters that trap sand and rust.

Use compensating equipment.

Compensators and water hammer absorbers- special devices that are capable of absorbing part of the liquid from common system when the pressure increases, thus reducing it.

If your home is supplied with water from an autonomous source using pumping equipment, then use hydraulic accumulator. It is part of pumping stations and is a tank with a rubber membrane, into which excess water will be discharged during a water hammer until the system pressure normalizes. A pressure switch is an element that will not save you from water hammer, but will turn off the pump when you turn off the tap and the pressure exceeds a certain value. It should be borne in mind that the pump will not turn off instantly. Use a pump with a frequency converter that automatically regulates its operation and ensures smooth start and stop. A sharp increase in pressure in the system, which leads to water hammer, is excluded.

A pipe made of elastic plastic or heat-resistant reinforced rubber can be used as a shock absorber, which will absorb the energy of the hydraulic shock.

Long pipelines, for example, heated floors, are most vulnerable to water hammer. To secure such a system, it is equipped with a thermostatic valve.

Thermostat with super protection. Sometimes a thermostat with special protection against water hammer is used. Such devices have a spring mechanism installed between the valve and the thermal head. If there is excess pressure, the spring is activated and does not allow the valve to close completely; as soon as the power of the water hammer decreases, the valve closes smoothly. Install such a thermostat strictly in the direction of the arrow on the body.

Diagram of the hydraulic shock compensator

The diagrams above show examples of how expansion joints should be installed correctly. They can be mounted horizontally or vertically, on cold and hot water collectors or on any section of the pipeline leading to the final point of water consumption.

Here it is necessary to pay attention to the fact that water should not stagnate at the entrance to the compensator, otherwise bacteria may begin to multiply in the system. Therefore, the instructions do not allow its installation at the top of the riser.

According to statistics, more than half of pipeline accidents are not due to corrosion or fatigue of materials. They are caused by water hammer in the water supply system. But they can be completely avoided if you immediately install the system according to all the rules and equip it with special devices that dampen the shock wave.

The protection measures listed above will be more effective if they are applied comprehensively, and you can always neutralize the unpleasant effects of water hammer and extend the life of pipes and household appliances.

Pressure plays an important role in the heating system. It is thanks to the pressure difference that the liquid moves through the pipeline. Pressure directly affects flow speed. But a sudden change in pressure in one side of the pipeline can provoke destruction of the pipeline, so water hammer compensators are installed in the system. They look like containers, divided into two parts using an elastic partition. In one part there is air, and the second is connected to the main line. As the pressure increases, the membrane bends into the area with air, and as the pressure decreases, the volume of air increases, which helps compensate for the water pressure.

You can buy water hammer compensators inexpensively in a store that specializes in selling goods for heating networks and water supply. A huge range of compensators allows you to make a choice in favor of one or another device that differs in quality.

You can wholesale water hammer compensators made from brass alloy. The inner membrane is made of durable plastic. The small size of the parts is a definite advantage for them. This simplifies their installation even in rather cramped spaces.

Buy water hammer compensators inexpensively

An affordable pricing policy makes it possible to buy water hammer compensators in the Uni-Fitt online store in large quantities. Such a system will ensure the protection of water supply, both in large-scale enterprises and in standard conditions. Water hammer compensators, the price of which is affordable, have a fairly good service life, provided that all technical specifications selected accordingly.

Buying water hammer compensators with delivery to any region of Russia will not be a problem for you.

Pressure, as one of the parameters of the heating and water supply system, plays a key role. It is due to the pressure difference that the fluid flow is formed. IN modern systems heating uses hydraulic pumps. The pressure indicator determines the flow speed, pressure and volume. In open systems, which were widely used in the past, the fluid pressure was equal to atmospheric pressure, so an increase in the temperature of the medium was accompanied by a flow of fluid into expansion tank.

The disadvantage of such a system was the gradual evaporation of the liquid, the inability to increase the boiling point, and vulnerability to hydraulic shocks.

The liquid is practically not compressible. When layers are compressed, large elastic forces arise, which can be transmitted at high speed in the medium. A sharp change in pressure in one part of the residential pipeline could lead to the destruction of pipeline elements in another part.

A water hammer can be triggered by opening a tap or any valve. A striking example is the destruction of a newly laid pipeline during its first start-up, when the water supply is opened with the mixer valves closed.

Closed heating system

If the pipeline is made airtight, then when the liquid is heated, the pressure will begin to rise sharply, which may cause pipes or connections to begin to collapse. However, pressure exceeding atmospheric pressure provides many advantages.

As is known, the boiling point increases, therefore, the carrier can be used more efficiently.
With increased pressure, the efficiency of the hydraulic pump increases.
The sealed system does not require periodic recharge.

The pressure regulator in a closed type system combines the functions of a membrane compensator and an expander. It is a container divided into two parts by an elastic partition.

One part contains air under pressure, and the other part is connected to the main line. During thermal expansion, the liquid presses on the membrane, causing it to bend into a zone filled with air. As the volume of air decreases, its pressure increases and begins to compensate for the excess pressure of the liquid.

When the apartment heating system is in working condition, the membrane compensator is in dynamic equilibrium. Every increase in fluid pressure is accompanied by an increase in air pressure. But it turns out that such a system is not only capable of dampening thermal expansion, but also works as a water hammer damper.

Diaphragm compensator device

On the market building materials and parts for heating systems, the expansion tank is known as a membrane water hammer compensator. It can be installed not only in the heating system, but also in the water supply system. The main purpose of the container is to unload the system in case of increased pressure.

The membrane, made of elastic material, is a pressure regulator. The shape of the tank is not subject to standardization. The choice of external form depends solely on the conditions of the surrounding space and aesthetics. The most common compensators are in the form of a cylindrical cylinder.

The half of the tank where the air is located has an outlet with a spool. Through it you can add or reduce the amount of air in the tank. When purchasing a membrane compensator, the air is under pressure equal to tenths of atmospheric pressure. During commissioning, this pressure increases according to the system parameters. The compensator has only one connecting pipe, because there is no through flow of liquid.

Varieties

There are several types of current device classifications. The most practical is considered to be grouping according to the types of membranes used. Today, almost all devices are produced with a diaphragm membrane. The cylinder is non-separable, made of durable steel. Usually consists of two hemispheres welded together. The membrane is mounted in such a way that the cavity of the tank is divided into two parts. The connecting pipe remains in one part, and the spool in the other.

The balloon membrane must be replaced. But modern materials are able to withstand increased loads for quite a long time without loss of integrity and elasticity, so the need to replace the membrane has practically disappeared. The reservoir for the balloon membrane is dismountable. The water is contained in a rubber chamber and does not come into contact with the inner walls of the tank. The spherical membrane is practically not used today; it is considered a rarity.

Installation rules

If previously certain installation requirements were imposed on the expansion tank, then in closed system The compensator can be installed anywhere. However, this is only a theoretical assumption. The requirements for location at the highest point are no longer relevant, since according to Pascal’s law, the pressure is the same everywhere.

The compensator is mounted where there are plumbing units, inputs or junctions.

On the one hand, this is due to the fact that the nodes are common cause water hammer, so it is more advisable to install a device that dampens excess pressure in close proximity to taps and valves.
On the other hand, aesthetics play a significant role here. Against the background of straight pipes neatly laid around the perimeter of the room, the cylinder will not look good.

An important installation condition is the absence of a long or curved outlet to the cylinder. Since water does not circulate in the outlet, this can lead to stagnation and, as a result, to the proliferation of microbes. Bends should be short and straight.

Based on these considerations, it is worth choosing the location of the compensator.

Overview of membrane compensator models

Comparison technical characteristics different models of devices helps those who are faced with the need to use them for the first time right choice. The same can be said about membrane compensators. The Valtec Car 19 model is ideal for domestic use in apartments.

Its main purpose is compensation variable values pressure in water supply and heating systems. Valtec models are often used exclusively as an expansion tank. The compensator body is quite durable; moreover, it is made of stainless steel. During a water hammer, the tank can hold 162 g of water. But this is not such a low figure, since the pressure in the line at this time is from 10 to 12 bar.

When installed, the nominal pressure in the tank is 3 bar, which in most cases is suitable for many systems without reconfiguration. Some models are equipped with pressure gauges for more convenient adjustment of the compensator.

The FAR FA 2895 12 model from FAR has won its niche in the compensating device market due to its reliability at a relatively inexpensive cost. Temperature and pressure indicators allow the compensator to work both in industrial systems and in home use systems.

The design of the tank is practically no different from its analogues. The material used is brass alloy, and the membrane is made of durable plastic. So that this plastic does not deform under the influence of air when the tank is empty, but is held in place by springs. The undoubted quality of far models is their small size; they are easy to install even in confined spaces.

Manufacturers Reflex and caleffi specialize in the production of fittings for water supply systems. They offer a whole line of expansion joints that differ in that they are used in larger systems. The Reflex tank capacity can reach hundreds of liters. Often such devices become hydraulic accumulators capable of storing huge amounts of water. Such batteries ensure the integrity of the pumps when the water supply is turned off.

The availability of devices and the flexible pricing policy of manufacturers makes it possible to protect water supply systems not only at large enterprises, but also in ordinary home conditions. The listed devices have a fairly long service life, provided that all technical parameters are selected correctly.

Residents of new buildings, upon accepting apartments, are surprised to discover “donuts” - loops on plastic hot water risers under the ceiling. Some simply hide behind a drywall box, others demand an explanation. Why is the pipe rounded? This is how the developer is trying to insure residents against pipe ruptures. You cannot remove the bagels, but you can replace them with a more aesthetic option.

What is water hammer and why is it feared?

Water hammer is a sudden and very strong surge in pressure in pipes. Capable of breaking connections and pipes themselves, tearing off valves and causing a flood. Small water hammers act gradually, over and over again squeezing out the gaskets, slowly but surely deforming and destroying water supply and heating pipes with microtraumas.

Externally, weak water hammer is recognized as vibration through the pipe, hum, popping, clicking or others extraneous sounds, which are especially annoying for residents whose neighbors get up earlier or go to bed later.

How does water hammer occur?

This is a phenomenon when in one section of the pipe the water has already stopped, and from behind it is pressed by masses that continue to flow:

when the watercourse is suddenly blocked;
when the pump starts abruptly.

In a heating system, water hammer is caused by air pockets.

Risk factors

What determines the force of water hammer:

Depending on how abruptly the constipation or start of the watercourse occurred.
The volume of water in the pipes and, accordingly, their size.
The speed of fluid movement and its pressure.
Pipe material.

Formula
Shock wave frequency = 2 pipe lengths / shock propagation speed in a particular material.

Wave speed in plastic is 300-500 m/s. For comparison, in steel - 900-1300, and in cast iron 1000-1200 m/s. It follows that in plastic the impact will be stronger, but cast iron liners actually dampen the water hammer.

What happens to the pipe?

Nothing good: it expands in breadth and shortens in length. Under pressure, the pipe may well burst. Faucets and connecting elbows suffer most often: seams come apart, gaskets move or break, and leaks begin.

From the memories of a locksmith
I’m in my third decade in the plumbing world, but I saw a real water hammer only once (1994) in an elevator unit<…>. Water hammer is when the arrow<…>flies away in one second from 8 bar to 60.

The worst thing is the water hammer in the elevator unit, pumping station and other public communications. Pipes in apartments are subject to vibrations to a much lesser extent, but it is worth understanding that the cross-section of modern risers is narrower (the pressure is correspondingly higher) than that of Soviet steel ones, and the material is more mobile and less durable. First of all, hot risers pose a danger - materials expand more when heated.

Protection measures

To avoid ruptures, special devices are installed on all risers in basements, and in apartments on hot ones, which prevent vibrations from destroying the pipes.

Locking devices, their pros and cons

These are wave, loop or U-shaped pipes made of ordinary or special material, for example, reinforced plastic or rubber, 20-40 cm long, the simplest and cheapest option.

Shock-absorbing connections are cheap, and at the same time they can withstand the water hammer that plastic communications in an apartment have to experience in practice; they do not require special maintenance or periodic replacement of parts.

Bellows shock absorber- corrugated pipe made of ductile metal, capable of compensating for linear expansion, elongation, or both phenomena at once, simpler - single-layer, more advanced - enclosed in a casing that provides additional shock absorption.

Bellows shock absorbers in a casing are also unpretentious, while being more aesthetically pleasing than the previous version.

Important
It is the shock absorbers-liners (especially loop bends) and bellows that are designed to compensate for the elongation of the riser; this is their main function, and the damping of water hammer is rather secondary. For plastic pipes, especially not of very high quality material, they are as important as expansion joints.

Shunts - metal tubes that are inserted into the pipe together through the main valve in the direction of water flow and bleed excess water behind the valve, are ineffective in old pipes clogged with rust, and are more suitable for plastic communications.

Shunts are easy to install and do not require opening the pipe, but they lose effectiveness in proportion to the clogging of the pipe, and in a domestic circuit this figure can be quite high.

(the most common - Valtec) - devices that resemble a ball or tank and are a cavity with an elastic membrane, which is pressed in with a sharp increase in water pressure, and then gradually expands, returning the water to the current, but without impact force.

Diaphragm compensators hold up to 30 bar, and this is a pretty good indicator. Their weak point is an elastic membrane, which over time becomes deformed, breaks or hardens due to salts and additives in the water.

Piston, or spring (the most popular today is FAR) - devices similar to a cap and operating on the same principle as membrane ones, with the difference that the membrane is replaced by a spring: when the volume increases, water pushes a plastic disk into the cavity and thereby compresses the spring, then the mechanism returns to its original position, returning water into the circuit.

Piston compensators can withstand surges of up to 50 bar and have ways to protect against real, not weak, water hammer. In addition, they are more resistant to wear than membrane ones, however, they are not immune to leaks at the seal or connection points with the pipe, so they need to be periodically checked and replaced.

Control valves- systems that are usually included in comprehensive protection against water hammer and are installed on controllers of external and general house circuits.

The bypass system is a jumper pipe that allows you to redirect the flow of water coolant in order to avoid water hammer and ruptures in the batteries.

Experts' opinion
Old-school locksmiths consider installing indoor extinguishers a waste of effort and money. According to them, a strong water hammer threatens the water treatment channels in the basement, and that’s all. Other craftsmen note that in earlier times all taps were closed slowly, using a valve, but now they are mostly lever (ball) taps, and household appliances (washing machines, dishwashers) and toilet tanks also shut off the flow of water quite abruptly. Therefore, ideally, the damper should be located in front of each such consumer.

Comprehensive preventive measures:

smooth closing of taps and valves;
pump power regulator, which slows it down at the first revolutions and prevents it from provoking a shock wave.

Actually, water hammer absorbers have always included “coils” - a wave-like bend of a hot water riser, led into the bathroom from the toilet. Housewives used it as a heated towel rail. In essence, the pipe slowed down the flow of water and eliminated vibrations, reducing the risk of water hammer. However, leaks appeared quite often at the junction of the apartments, especially over the years.

Metal ages faster than high-quality plastic, the installation of ball valves significantly increased the load on the structure, and the difference in materials, when plastic was placed on top and metal was left below, or vice versa, makes itself felt. Because of this, the “coils” do not work.

How to install

General rules:

the shock absorber is installed on a certain length of pipe (for example, under the ceiling of each odd-numbered floor);
the best option is when the compensator is located in front of the valve, faucet, valve of household appliances, faucets, and other consumers;
It is also permissible to place the compensator after the collector outlets (i.e. after check valves) in the apartment (see photo below from S. Savitsky’s blog “Ideas for renovation”);
if a gearbox is placed, the compensator follows it;
the compensator must be located directly on the pipe or on a corner transition, and not on its dead-end branch (see photo below);
the shunt is installed strictly in the direction of water flow;
the regulator or valve is placed near the controller and connected to it.

Okay, we figured out the pipes and risers. What to do if the house has an electric storage water heater or a gas water heater? The former are usually equipped with their own safety valves. In the case of a “column” or any other instantaneous water heater, the compensator should be placed after the unit - this will extend the life of its hoses and seals.