"BigWallop" wrote in message
...

"John" wrote in message
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"BigWallop" wrote in message
k...

"waddy" wrote in message
oups.com...
Do you need a double check valve when connecting the water mains to a
combi boiler without using any break tank?


Yes. It stops water being sucked back from the heat exchanger in the
boiler,
and, mostly, to stop water getting back to the mains from the filling
hose
to
the central heating loop, which will contain rust inhibitor and other
chemicals.



You can I suppose quote which bylaw asks for this? (The cold mains in to
the
DHW part, the fill loop should include a N/R valve anyway)


Here's just one:
http://www.surreycc.gov.uk/sccwebsit...e?opendocument

But there are plenty more, if you want me to list them for you?


Well I looked at this link but couldn't find anything asking for a N/R valve
on the inlet to a combi (plenty about hoses and horsetroughs which I'm
familiar with). I'm off to look for my copy of the current bylaws but ISTR
(fairly sure) there is no requirement to have a N/R valve on the cold mains
inlet to a combi. Some older combis had an expansion vessel in the tapwater
circuit but later models rely on any thermal expansion of the potable water
relieving back into the pipework. If there was a N/R valve fitted this would
be impossible.

John