Mains water pressure varies from below 1 bar (insufficient for most dwellings) to above 10 bar. There are extreme areas where pressures of 18 bar have been supplied to domestic dwellings and pressures above 20 bar to commercial property.
The average supply pressure is 3 bar during the day (it may be considerably higher at night) with approximately 20% of the country above this at some time. These areas would benefit from the use of pressure reducing valves.
What is a Pressure Reducing Valve?
A pressure reducing valve is a valve that reduces a higher upstream pressure to a lower downstream pressure under flow and no-flow conditions.
Why Install a Pressure Reducing Valve?
The majority of water pipe infrastructure is ageing at a considerable rate mainly due to the conditions they operate under. Metallic pipework that is buried is subject to corrosion attack from moisture, aggressive soils and stress from surrounding ground conditions.
Water company and commercial underground or overground pipework is subject to similar conditions but are usually so critical to the business little or no maintenance is carried out. This can lead to catastrophic consequences such as lost production and damage to machinery and property.
Install a pressure reducing valve to relieve pressure inside the pipework and extend the working life until a time when renewal is the only option.
Leakage can be difficult to quantify especially if small leaks are undetected over long periods of time. These small leaks compound and increase consumption and bills gradually, un-noticed by the consumer. If there is a large distribution system detecting leaks can be time consuming and expensive to locate.
Install a pressure reducing valve to relieve pressure and therefore reduce flow through leaking joints. This will have a universal effect on all leaks reducing consumption and bills from water authority.
How does a Pressure Reducing Valve Work?
Under no flow conditions the down stream (outlet) pressure acts on the diaphragm and overcomes the spring pressure. The diaphragm moves up and the linkage that joins the diaphragm to the seat holds the seat closed so down stream pressure cannot increase.
Under flow conditions the downstream (outlet) pressure decreases until the spring can overcome the pressure.
The diaphragm moves the linkage down and so opens the seat and water flows through the valve. When the outlet is closed, pressure builds up until the spring pressure is overcome and the seat is closed again.
Balanced pressure valves operate in basically the same way except there is an additional "piston" of the same area as the main seat. This gives better control under low and high flow conditions.
An Example of a Commercial Under Pressure System
On the lower level, where you would typically have the building supply plant, a high pressure pump-set and hot water heater are represented. The output of the pump set would be controlled by a pilot operated pressure reducing valve, which in turn would supply the risers with a stable controlled flow of water but still at a relatively high pressure (to overcome gravity).
On the middle level, where the pipe sizes are 1", dial up pressure reducing valves are shown, which are designed for industrial and heavy commercial systems. These are one piece replaceable cartridge type pressure reducing valves, with a mechanically operated set pressure indicator dial and an integral strainer.
Also shown is a valve which is an economy FBSP valve that can be supplied either with an adjustable outlet pressure or with a factory set and locked outlet pressure.
On the top level, where pipe sizes are smallest, adjustable pressure reducing valves are shown, which are one piece replaceable cartridge type valves with 1 /4 " gauge ports for setting up and monitoring downstream pressure.
Also shown is the tenant valve pack, which is a combination valve assembly consisting of an isolating ball valve, integral double check valve, dial up pressure reducing valve and a single jet water meter.
The unit comes fixed to a bracket and is particularly suited to high rise blocks of flats and offices, which require isolation, pressure control, backflow protection and independent water usage monitoring.
The system diagram(shown to the left) is designed to show the various applications of pressure reducing valves and where in a system valves could be fitted. The diagram is a snapshot of a high rise type of installation.