Pressure Reducing Valves & Accessories

As UK Plumbing systems become more advanced and plumbing equipments becomes more sophisticated, mains pressure is being increasingly used in situations that used to be the domain of the low pressure gravity systems: e.g. unvented hot water heaters, continental style multi outlet showers, electronic controls. As the use of such systems and specialised fittings becomes more common, so too does the use of pressure reducing valves in order to control and regulate pressure and flow to the terminal fittings.

In the UK, water pressure from the mains can vary from between 1 bar to 20 bar, and in some places at low usage times the pressure can be even higher than that. The water pressure is also variable throughout the day, with pressure increasing at night and in the middle of the day but dropping at high usage times: early in the morning and late in the afternoon. Generally, for most domestic applications a pressure of around 3 bar is sufficient if the internal plumbing system is designed and installed correctly. Water pressures above 3 bar can start to cause problems such as excessive noise from the high flow velocity, water hammer from ceramic disc taps, solenoid valves and ultimately higher water bills. One simple way to prevent these difficulties and protect the plumbing systems from over pressurisation is to install a pressure reducing valve at the entrance to the property which will limit the and maintain the incoming mains pressure to the desired level.

Many pressure reducing valves contained within this catalogue are balance spring and diaphragm type valves that will limit the downstream pressure to a pre-determined maximum under flow and no-flow conditions. A valve that works under both flow and no-flow conditions is described as ‘drop tight’. The most important criterion for a pressure reducing valve is that it must be ‘drop tight’, i.e. pressure does not increase downstream of the valve under no-flow conditions. It must be emphasised that 99% of pressure reducing valve applications require the pressure to be limited to a maximum predetermined level under flow and no-flow conditions. Another term that is used in relation to the operation of a pressure reducing valve is ‘creep’. This is a slow or small increase in downstream pressure under no-flow conditions. A valve that allows this can not be considered to be ‘drop tight’ or in fact a true pressure reducing valve as what will happen is a slow build up in outlet pressure until it equals the inlet pressure.

There are many different applications for PRVs. Basically, they can be used just about wherever water pressure needs to be controlled. If you would like advice as to a specific valve for a specific application, please contact us and we’ll be happy to provide technical assistance.