082 HPM 0415

HPM April 2015

Got a story? Ring us on 01732 748041 or e-mail twood@unity-media.com PIPES,PUMPS,VALVES&FITTINGS Water fitting regulations and pumps Dr Steve Tuckwell, WRAS technical advisor, looks at the requirements of the Water Fittings Regulations and Byelaws regarding water pumps... Section 65 of the Water Industry Act (2003) sets out water suppliers’ obligation to provide a minimum water pressure in their water mains and other pipes providing supplies of water for domestic purposes or which have fire hydrants fixed on them. It requires a constant supply at a pressure which will enable water to reach to the top of the top-most storey of every building within the supplier’s area. But the Act says the water supplier doesn’t have to provide a supply of water at a height greater than that to which water will gravitate through its water mains from the service reservoir or tank which provides the supply. The water regulator for England and Wales, Ofwat, has a guaranteed standards scheme which sets a minimum pressure of seven metres static head (0.7bar) in the premises’ underground communication pipe. Ofwat monitors the number of premises where water suppliers fail to meet this standard and encourages them to reduce this number by investment in improvements. Where pressure is insufficient for users’ needs, pumps may be needed either on the supply pipe, to boost it throughout the entire premises, or on the pipe serving specific appliances, like domestic showers. But, as all good installers will know, there are some conditions attached to the use of pumps. CONSENT FOR A PUMP Throughout the UK, plumbing systems supplied with water from the public system come under the scope of the Water Supply (Water Fittings) Regulations or the Scottish equivalent (the ‘regulations’). These require that the water supplier’s consent is obtained before installing a pump or booster drawing more than 12 litres per minute, connected directly or indirectly to a supply pipe. Without this consent, the installer would risk a criminal prosecution for breaching the regulations. Consent is obtained by notifying the water supplier in writing of the details of the proposed installation. Water suppliers websites usually give details of what information is needed and where to send it. Some have notification forms to download to make it easier. Note that the regulations refer to a pump “connected directly or indirectly to a supply pipe”. This means that consent is needed not just for a pump on the supply pipe (Figure 1) but also for one on a distributing pipe fed from a WWW.HPMMAG.COM 82 APRIL 2015 HEATING & PLUMBING MONTHLY enquiry number 160 cistern (Figure 2). At a recent WRAS Technical Committee meeting representatives of the water suppliers who enforce the regulations confirmed that notification was required where, based upon the manufacturers’ specifications and flow curves, a pump is capable of delivering flow above 12 l/min. NEGATIVE PRESSURE The risk of creating backflow conditions is the reason for the concern about using a pump to boost flow on a supply or distributing pipe. A negative pressure could arise in the upstream pipe if the pump demands more water than the supply into the system can provide. Where there are other connections for outlets supplying appliances upstream of the pump, the negative pressure at these connections could cause contaminated water from the appliances or outlets to be drawn back into the system. So, where pumped showers or other appliances supplied through or incorporating pumps are installed, care should be taken in positioning branches from distributing pipes. The Water Regulations Guide (Section 6 para R15.8) recommends that pipework installations should be designed to provide the calculated simultaneous demands of the system, but due allowance should also be made for those devices where a full demand is required at all times. This is particularly relevant in distributing pipe systems where branches serve pumped showers or other appliances. No pumped showers, or other appliances incorporating a pump, should draw water from any supply or distributing pipe which serves an appliance categorised as fluid risk four or five, for example, a pipe serving a bidet with an ascending spray and/or a flexible hose and spray/jet. FIRE SPRINKLER SYSTEMS AND PUMPS One application where a booster pump on the supply pipe is often requested is to provide adequate pressure for fire sprinkler systems in tall buildings. In considering the request for consent, water suppliers may use sophisticated mathematical network analysis to assess the ability of their mains networks to meet the demand without causing loss of pressure to other local customers or in key parts of their supply area. Some fire sprinkler installers mistakenly believe that the water supplier has the legal duty to supply buildings with sufficient water for fire fighting, whereas the Water Industry Act only requires water to be available at hydrants on the supplier’s water main. The location of these hydrants on water mains is usually at the request of the local fire authority but may be specially requested by factory owners or occupiers. BREAK TANKS AND BOOSTER PUMPS Where the use of water in a process or application creates a backflow risk which requires fluid category five (FC5) backflow protection, one method is by using a breaktank with an airgap rated for FC5. These are type AA, AB or AD airgaps. Although the break tank protects against backflow, water pressure from it can be too low for process or appliance needs. If the downstream application requires good water pressure, a booster pump is needed. Figure 3 shows this arrangement – in this example for supplying outlets and appliances in a laboratory. Figure one Figure two Figure three


HPM April 2015
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