Feeling the pressure
By Patrick Gordon of Calafrica ( technical @ calafrica . co . za )
Patrick Gordon takes us step-by-step through installing a pressure reducing valve in line with SANS 10254 .
TECHNICAL 35
Images supplied by Patrick Gordon
The next item in the water supply to the hot water cylinder is the pressure reducing valve and the expansion relief valve . You may ask why it is mentioned separate if both these functions are incorporated in one valve . Traditionally we would refer to them as a pressure control valve .
SANS mentions them separate as provision is made in the regulations for them to be installed separately . In the previous article we mentioned that if there is an isolation valve installed after the pressure control valve , an expansion relief valve should be fitted on the cold-water line after such isolating valve .
SANS 10254 ED4 2022 5.8 Expansion control valve on cold water supply When an expansion control valve is installed on the cold-water side of the water heater , it shall be installed downstream of any isolating valve , gate valve , non-return valve or any other flow-control device .
5.9 Pressure control valve 5.9.1 The actual position of the pressure control valve in relation to the water heater in the plumbing system will be influenced by the various pressure and friction losses that develop during operation .
To ensure an effective operating pressure in the water heater , these factors should be effectively controlled .
5.9.2 The position of the pressure control valve shall be downstream of all high draw-off terminal fittings , for example , garden taps and mains-fed toilet flush valves .
This now instructs us as to where the valve should be situated , but what should the pressure rating of the valve be ?
4.3.2 Pressure rating of the system The rated pressure of the system shall not exceed a static pressure of 600kPa ( see SANS 10252-1 ) and the pressure control valves , and expansion control valves used in the system shall have the same pressure rating . This pressure rating may be less than the rated pressure of the storage water heater but shall never exceed it .
April 2024 Volume 30 I Number 2 www . plumbingafrica . co . za