Where should isolating valves be positioned?

Guidance on the positioning of isolating valve

A full-flow isolating valve should be positioned on the cold feed into the WWHRS unit, along with a double check valve a second full-flow isolating valve should be positioned on the pre-heat out of the WWHRS unit. Full installation guides are available here.

Isolating valves should be located close to the unit, The one located on the feed side after any other branch from the balanced water, and on the pre-heated side before any branch.

The isolating valves will normally only ever be used in the unlikely case of there being a leak and the unit needing replacement.

• In practice
  • If there is a leak during installation at first fix, the unit can be isolated and removed
  • If there is a leak post-occupation, typically the first place a homeowner will go to stop any leak is to the main stop cock, rather than search out an isolating valve for a specific product.
  • For a Pipe HEX that is boxed in, an engineer coming to fix a leak will have to cut through the plasterboard to check the leak, and at that stage can isolate the unit from the rest of the supply and turn the water back on at the main stop cock.
• The final decision for the valve locations is always down to the M & E Designer/House builder, but: -
  • For a Pipe HEX vertical system having them in the boxing is best – If an engineer did ever need to cut into the boxing it will normally be at the bottom near to where a leak has been detected. They will then have access immediately to the valve and be able to isolate.
  • The valves could also be located close together at high level either in the boxing or just outside, so that both are accessible at one point. However, with so many different house designs and layouts, it would be very difficult to advise on where they are located and potentially mean damage caused trying to locate them.
  • If it is a System A or C installation, the leak would be impacting on the hot water for the home as well, and need to be treated urgently. So the water can remain shut off at the main stop cock until the unit is accessed.
• In reality, a well-installed unit should not need to be accessed, however, If the isolating valves are located away from the unit they do become difficult to locate and once shut-off, there is more water to potentially leak out during removal.