By Peter Telle
Water pressure from the municipal mains is too high in most residential complexes. Taps, geysers etc are efficient at 4bar. There is the danger of broken equipment and even broken pipes if the pressure is substantially higher.
The installation of a pressure reducing system is the only way to resolve this.
The following information is required to design a stable and efficient pressure reducing installation.
● What is the pipeline size? In most cases if the pipe size is say 100mm, one can use an 80mm valve.
● What is the maximum inlet pressure (feed from municipal mains)?
● What is the minimum inlet pressure?
● What is the difference in elevation between the location of the PRV and the highest and lowest points to be serviced. This is used to ensure that the pressure range is between 3 and 6 bar anywhere in the service area.
Pilot operated pressure reducing valves become unstable at the low flows expected in a well-maintained residential complex. A smaller bypass direct acting pressure reducing valve is normally installed to take over pressure control during low demand periods.
A small relief valve should be installed on the downstream side to cater for delayed reaction times during rapid demand reduction. This valve would normally be set approximately 2 bar higher than the main pressure reducing valve. It will protect the pipeline during the opening and closing of the main pressure reducing valve.
Experience has shown that it’s a good idea to install a strainer upstream of the pressure reducing system. Installing an isolating gate valve upstream and downstream of the system allow for easy maintenance.
It is advisable to order the complete “PRV Station” as a unit all bolted together so that the plumber (or contractor) cannot make a mistake while installing it