DHW iso valve

[hedid2003]

Hi All

does anyone know why there must not be an isolation valve installed to the domestic hot water outlet on a combi boiler?

 

[doitall]

Why would anyone want too ?. There should be an local isolating valve on every outlet.

 

[hedid2003]

Thanks for replying.
The reason why i ask is that the way somebody interpreted to me is that it was some kind of water reg?Also what do you mean by local isolation valves?

 

[45yearsagasman]

what do you mean by local isolation valves?

Valves that are fitted just before a tap for example. Good practice, as the whole system doesn't have to be shut or drained to change just one tap washer.
A combi will have a iso valve on the cold inlet supply and a valve on the outlet is not required.

 

[mysteryman]

Most combis have a cold water inlet iso valve. This shuts off all dhw supplies to the building. Some combis had a hot outlet iso valve as well, which could be useful when working on the dhw part of the boiler. I don't think this is illegal, although it would not be good on a storage combi.