By Patrick Gordon, technical manager, Splashworks
Before we discuss this, we need to look at what the law requires.
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.
SANS 10254 Drg 11744:
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.
In this type of installation, it makes sense to fit a pressure control valve that does not have an integral isolator as they are less expensive, and an isolating valve still needs to be fitted in any case.
Considering these points, it is obvious that we must re-look at the way that we currently do installations so that we can stay in line with what is required by law, and also to deliver the cost-effective user comfort that our customers are used to.
© Plumbing Africa
