TECHNICAL 33
Why should I fit an extra isolating valve if my geyser valve already has one?
By
Patrick Gordon, technical manager, Splashworks
Before we discuss this, we need to look at what the law requires.
SANS 10252-1:2018( Edition 3.2) 6.1.3 Isolating valves 6.1.3.1 Unless otherwise required, or provided that 6.1.3.2 does not apply, a specific isolating valve shall be provided
c) where a pipe enters any building or any portion of a building in separate occupation,
SANS 10254 Drg 11744:
Taken from SANS 10254
Here SANS requires us to install a specific isolating valve where the pipe enters the building, or in the case of apartments etc. that have multiple dwellings that make up a building, every place that there is a water supply that enters the building. There is one exception to this rule and that is contained in 6.1.3.2.
6.1.3.2 Notwithstanding the provisions of 6.1.3.1, an isolating valve shall not be provided between any pressure reducing valve and a water heater if such a pressure reducing valve incorporates an expansion relief device or vacuum relief device intended to protect such water heater.
Here it tells us that if there is a pressure reducing valve with an integral expansion valve, the specific isolating valve must be before the pressure valve.
What does this mean? If you have a balanced pressure installation( like we should), with the valve positioned outside the dwelling, you are not allowed to fit any flow control device between the hot water cylinder( HWC) and the expansion control valve. Having such a device can prevent the HWC from the route to expand.
It has become common practise to fit an isolating valve near the HWC so that the dwelling can still be supplied with water when the HWC needs maintenance or replacement. This practise can continue with the proviso that a separate expansion valve is fitted between the isolating valve and the HWC. Therefore, still allowing for any expansion to be effectively vented.
The integral isolating valve that is incorporated in some of the pressure control valves cannot be classified as a specific isolating valve. When any replacement of the pressure control valve needs to take place, you still need a separate valve to isolate the water.
Supplied by Advanced Valves and Splashworks
June 2026 Volume 32 I Number 04 www. plumbingafrica. co. za