As the UK plumbing systems become more advanced and plumbing equipment becomes more sophisticated, mains pressure is increasingly being used in situations that used to be the domain of the low pressure gravity systems: i.e. 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 (PRVs) in order to control and regulate the pressure and flow to the terminal fittings.
 However, all pressure reducing valves are not created equal and despite the claims of some manufacturers only compliance with the British and European standard BS EN 1567 and the UK water regulations (WRAS approval) will ensure that the pressure reducing valve is truly fit for purpose. If we look specifically at the standard we can see why it is so important: valves that are built and tested to this standard must comply with a rigorous test regime which is designed to make sure the that the valve will function correctly under both usual and unusual system conditions. The standard is broken down into various sections, each one looking at a particular function of the valve. Among the main areas tested for the standard is performance. This includes checking the valve’s flow rate under changing inlet pressures and under inlet pressures that are below the valve’s set outlet pressure, checking the valve’s pressure reduction ratio (should be in the region of 10:1), and probably most importantly checking whether or not the valve is drop tight under static conditions: ie the downstream pressure does not slowly creep up to eventually equalise with the upstream pressure.
No Noise is Good Noise
Another component of the standard is meeting specific acoustic requirements. In continental Europe noise pollution caused by high velocity water running through plumbing systems has for many years been considered a much more significant factor than in the UK. This may be in part historic because of our love for the low pressure gravity type system, where sufficient velocity to get water out of the tap at all is considered a bonus, hence noise was not an issue. In the modern UK residential plumbing system, it is becoming more common for high pressure mains fed or pumped systems to be used, and in multi unit buildings you are far more likely to see a high pressure boosted water main delivering water to the distribution system than the traditional gravity fed system, indeed this has now become the norm. It is in these types of systems that noise can be a big problem and, since a pressure reducing valve by its very nature is a restrictive device which can amplify the noisy system, it makes sense that the standard covering the performance aspects of these devices should put a limit on the decibel level that can be created by water running through the valve. In this standard the allowable noise level is 20db: the equivalent of a whisper, and any product that claims compliance to BSEN 1567 must meet this requirement.
How much is too much?
In the UK water pressure from the mains can vary from between 1 bar to 10 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 pressures increasing at night and in the middle of the day but dropping at high usage times first thing in the morning and late in the afternoon. Generally speaking 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, and water hammer from ceramic disc taps, solenoid valves on dishwashers and washing machines or other quick closing valves. It is also wasteful, as higher pressures mean higher flow rates and ultimately higher water bills. Additionally, many modern plastic plumbing products are susceptible to rapid deterioration if exposed to water pressures above 10 bar for any length of time, which can result in sometimes catastrophic failure and significant property damage. One simple way to prevent these difficulties and protect the plumbing system from overpressurisation is to install a pressure reducing valve at the entrance to the property which will limit and maintain the incoming mains pressure to the desired level.
Applications
 There are many different applications for PRVs: basically they can be used just about anywhere that water pressure needs to be controlled. There are however certain types of Reliance PRVs that have been developed with particular applications in mind.
Reliance's 6247 series PRVs DN65, DN80, DN100
suitable for industrial and commercial applications |
Commercial Sector
The 315 HC series PRV is very popular for the commercial market and is used extensively in areas such as high rise property developments, hotels, sports stadiums, schools, prisons, leisure centres etc. Several features make the 315 HC series attractive to the commercial market.
 1. It is a dial up type PRV. This means the valve has an indicator dial which will move as the adjustment knob is turned. The indicator will show the downstream pressure that the valve is set at, to within 0.2 of a bar. This feature can save significant time and cost when commissioning a large system.
2. The valve is full cartridge type construction, which means only one spare part ever needs to be kept to fully service the valve, and saves significantly on downtime if repairs are required as a full cartridge change can be done in less than a minute.
3. The 315HC series valves are suitable for cold and hot water up to 90°C, meaning that only one valve needs to be specified and only one range of spares needs to be stocked.
4. As this valve is targeted specifically at the commercial sector which can have significantly higher peak time demand for flow rates the valve has been designed to give maximum flow with the absolute minimum pressure loss.
Reliance has also developed a third generation valve group called the Tenant® Valve Assembly around the PRV cartridge. This is a combination type valve which incorporates an isolating ball valve, double check valve, pressure reducing valve, with all the benefits of the Reliance PRV, and a provision for a water meter cartridge all in one compact valve. It is ideal for any multi-unit development for zone isolation, backflow protection, pressure control, and if required, water metering.
Domestic Sector
 Reliance’s 320 Easiset® PRV is the ideal pressure reducing valve for the domestic market. Because issues such as servicing and maintenance are just as important in the domestic property as they are in a commercial one, the 320 Easiset range also incorporates our patented one piece cartridge type construction and the valve is available for temperatures up to 90°C. The biggest innovation though is the pull and twist adjustment mechanism which eliminates the need for cover caps and difficult to access adjustment screws. When the cap is pulled up and turned, the pressure is adjusted. Once this is completed, the cap is pushed back down and automatically locks in position. This new range is available in ½”, ¾”, 15mm and 22mm compression sizes and in hot or cold water versions.
As the UK moves closer towards the North American/Continental style of high pressure water systems, new and innovative products will be required to ensure that the provision of water to the end user is achieved in a controlled and efficient manner. Reliance has been at the forefront of pressure control in the UK for 20 years and will continue to provide easy to use, reliable, maintainable, quality products for pressure reduction for many years to come.
If you would like further information or to order any of our products please contact our Sales department:
Freephone (UK only): 0800 389 5931
Telephone - Rest of World: +44 (0) 1386 712400
Freefax (UK only): 0800 389 5932
Fax - Rest of World: +44 (0) 1386 712401
Email: sales@rwc.co.uk
Web: www.rwc.co.uk
Eric Winter, Technical Manager
April 2008 ©Reliance Water Controls Ltd 2008 | 