Water pressure reducer in the water supply system

Recommendation points

• Why do you need a pressure reducer
• Device: how the reducer works
• Types of plumbing systems requiring stabilization
• General and local installation
• Setting up and troubleshooting

The need to stabilize the working pressure in the water supply is not always obvious. Meanwhile, the gearbox in some conditions is simply necessary for the safety of equipment and the plumbing system as a whole. This will be the topic of our review: types of gearboxes, their installation and configuration.

Why do you need a pressure reducer

The pressure at the point of analysis of the water supply does not always correspond to the norm. Rather, even so: it almost never corresponds to the norm, and if the pressure is below the standardized one is just an uncomfortable phenomenon, then with a high pressure, very specific technical problems may arise.

The reason for this discrepancy is simple: standards are written by people who have little idea of ​​the details of the technical implementation for their compliance. For example, in high-rise buildings in Moscow, maximum norms are set at 4.5 and 6 kgf / cm² for hot and cold water supply, respectively. The fact is not taken into account that the natural gravitational pressure difference in any riser is about 1 kgf / cm² for every 10 m of height. Such restrictions would not allow hot water to be supplied above the 15th floor without a corresponding excess of the norm at the lowest point of draw-off.

The pressure is deliberately increased, and this is, in principle, a normal practice in high-rise buildings, but only with the use of special technical means. Without them, residents of the lower floors are at risk: the main system is able to withstand high pressure and its surges, but what will happen to household plumbing, even if the systems based on cross-linked polyethylene, which are considered the most reliable today, are designed for pressures up to 10 bar?

An example of connecting a reducer at the inlet of cold and hot water in an apartment. 1. Ball valve. 2. Check valve. 3. Water flow meter. 4. Reducer with pressure gauge. 5. Coarse filter

Water reducers belong to special means that protect internal plumbing from overpressure and water hammer. Their installation almost always falls on the shoulders of residents and is required not only in the lower floors of high-rise buildings, but also in any other places where periodic pressure measurements show a deviation from the norm, the pipes make a lot of noise during the flow, and it is even possible that the pressure from a nearby collector the moment of switching makes the pipeline tremble quite noticeably.

Device: how the reducer works

The main task of the water supply pressure reducer is to stabilize the outlet pressure and maintain it in a given range, regardless of instantaneous changes in the inlet, while ensuring the nominal flow. And although you can count dozens of types of gearboxes in plumbing stores, almost all of them solve their problems due to the equally arranged piston mechanism.

According to the principle of its operation, the reducer is similar to a valve valve: a rod and a wide piston in a narrow seat regulate the clearance, limiting the water pressure. The only difference is that when the piston is in a static position, the outlet pressure will always change in proportion to the inlet pressure, while in the reducer, the piston position is determined by the ratio of the current pressure and the stiffness of the adjustable spring. Adjustment of the gearbox “on the fly” is possible due to the so-called pilot circuit: if the pressure in it rises, the valve redirects the flow to the diaphragm, which lowers the piston rod and reduces the flow area.

In addition to the basic mechanism for regulating pressure, the most advanced models of reducers may also include some of the following additional devices:

1. Output pressure gauge. It is necessary to monitor the correct operation. The adjusting handwheel of the gearbox usually has a graduated scale, but the resulting deviation can be about 0.5 bar.
2. Coarse mesh filter. Internal ducts of household gearboxes are very sensitive to clogging and the removal of small debris from the water is critical.
3. Air relief valve. This assembly helps to avoid malfunctions and noise caused by airborne air.
4. Ball valve. Allows to combine the function of shut-off valves in the gearbox for installation at the entrance to the system.

Types of plumbing systems requiring stabilization

Reducers are installed not only in multi-storey buildings, where there is a danger of overpressure. The very ability to equalize the head is very attractive for increasing comfort. The pressure in the cold water and hot water supply pipes is almost always different, because of this, incorrect operation of the mixers is possible. Pairing pressure regulators can solve this problem..

The danger of water hammer is also inherent in autonomous water supply systems, for example, when powered from a well. Due to the incorrect operation of the check valves, a vacuum is created in the main pipe, which increases the pressure when the pump is turned on. Such a dynamic load has a very negative effect on both the pumping equipment and the water supply system in general, and in particular on the compression fittings..

The installation of a pressure regulator may be required to maintain the warranty for many types of household and heating equipment. These include water heaters, boilers with direct automatic feed system, washing machines and dishwashers.

General and local installation

The set of rules for water supply and sewerage states that the installation of pressure regulators should be carried out immediately after the valves at the input, that is, before the metering devices. This sounds sound, because in this case the gearbox will protect all hydraulic devices, including the meter and the filtration unit..

But when installed before the metering unit, any possibility of water intake should be excluded, which means that the technical plugs for flushing the filter and stem will be sealed, and the gearbox itself will be deprived of the possibility of maintenance. This can be neglected, but even in this case it is very difficult to provide for different hydrodynamic resistance and achieve equalization of pressures in the cold and hot water collectors. It is necessary either to install additional pressure gauges in them for more accurate adjustment, or to place pressure regulators immediately in front of the manifolds, as most experienced plumbers do..

If it is not possible to install at the input of the system, but some units require protection from overpressure, local installation is also possible. There are quite a few primitive models of gearboxes for 20 mm pipe threads, and even without fine adjustment they can quite cope with their protective function.

Setting up and troubleshooting

It is considered the optimal and most convenient water pressure at the outlet of the tap in 2-3.5 kgf / cm². But this value is not always easy to achieve, especially considering the need to normalize the static pressure when the water outlet is closed and the water does not move..

All gearboxes have different speed. When a flow appears, the pressure drops by 0.5–1.2 atm, depending on the current setting. After a few seconds, the pressure rises again (if the pressure at the inlet of the reducer allows it), but not to a static level, but slightly lower. Ideally, the outlet pressure should be at least 1.5 kgf / cm² below the input value, otherwise the water flow will slow down too much. This should be taken into account when adjusting the operating pressure of the pumping station..

A faulty reducer usually does not allow water to pass through at all or simply does not reduce the pressure, which can only be noticed when the pressure gauges are installed in pairs or there is a draw-off to the reducer. Maintenance of the device consists only in flushing the mechanism and the built-in filter. If this does not help, there is a mechanical problem or the influence of time. However, the entire regulator mechanism is clearly visible when removing the stem.

Breakage may include a broken spring, worn piston or diaphragm. Not all spare parts can be found on sale, but if they or a donor are available, replacement will not cause difficulties due to the availability of the main gearbox mechanisms for maintenance.