Water pressure regulation in tall buildings

I wrote the following article in 2009 as one of my monthly contributions to the training section of a leading heating and plumbing magazine, on behalf of a leading manufacturer serving those industries.

Water pressure regulation in tall buildings

Pressure regulation is necessary in tall buildings to ensure a constant and appropriate ideal water pressure at each outlet on every level. If the head pressure from the mains (or a booster set) is adequate on the top level of a tall building –2 bar, say – it may be too high on lower levels.

The water system in a tall building is rarely supplied directly from the mains, but usually fed at a high pressure by a booster set. This ensures delivery to the top floor at adequate pressure –say, 2 bar. However, without pressure regulation, the pressure would be higher on each floor, from the top downwards, with outlets on the ground and underground levels delivered at the full booster output pressure.

These pressures might cause pressure damage to pipework and would be far too high for washbasins, sinks, toilets, laundry and kitchen equipment. Pipes and appliance hoses are more likely to leak, appliances will not operate correctly and the system noise will be much higher, causing alarm to building occupiers.  In addition, a higher pressure means much more water is wasted while taps are left running to wash hands.

It is also necessary to regulate cold water supplies to the hot water system.

Therefore, a pressure reducing valve should be fitted in the supply to each level to ensure water is delivered at the required pressure, all the way down the building.

Reduce pressure in stages
When reducing the pressure supplied by a booster down to useful levels, it is good practice not to reduce pressure in one step by a factor of greater than 5:1. So, despite a valve such as the Honeywell D06F being rated at 25 bar, pressure should be reduced in stages. For example, if the booster set provides 18 bar of water pressure, it is recommended that you fit two valves in series, allowing a good gap between the two valves: the first to 6 bar and the second to 1.5 bar.

Modern buildings are often subdivided into units with differing needs. A hospital, for example, has many types of equipment connected to the water supply – from medical equipment to laundry machines – in addition to wash basins and toilets.

In such cases, cold water supplies to the hot water system might be regulated by DN65 to DN200 diameter valves installed in the main plant room. Then each department or unit may have its own cold water feed, so numerous small and intermediate-sized valves – from DN15 to DN50– may be installed on each floor to regulate individual supplies to units.

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