Do you need a double check valve when connecting the water mains to a
combi boiler without using any break tank?

"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.

"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)

"John" wrote in message
...

"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?

BigWallop wrote:

"John" wrote in message

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

"Horse Pasture Management Project", yup I can see how that might apply ;-)

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

I think you are confusing the heating circuit, with the DHW mains input.
The heating circuit will have a filling loop that incorporates a double
check valve. The DHW input does not need one.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

"BigWallop" wrote in message
...

"John" wrote in message
...

"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

"John" wrote in message
...

"BigWallop" wrote in message
...

"John" wrote in message
...

"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


Back again. Here's what I was trying to recall:-

Quote-

Backflow prevention

15. - (1) Subject to the following provisions of this paragraph, every
water system shall contain an adequate device or devices for preventing
backflow of fluid from any appliance, fitting or process from occurring.

(2) Paragraph (1) does not apply to-


(a) a water heater where the expanded water is permitted to flow back into
a supply pipe,

end quote

In article ,
John Rumm writes:

I think you are confusing the heating circuit, with the DHW mains input.
The heating circuit will have a filling loop that incorporates a double
check valve. The DHW input does not need one.

I'm pretty sure my multipoint water heater (a sort of combi minus
the central meating part) explicitly forbids the use of a non-return
valve on the mains, as it expects a small amount of expansion back
down the mains when you shut off the hot tap and it heats the final
cold water entering the heat exchanger.

--
Andrew Gabriel

Thnx John, that will do for me