Do I need a non return valve?


Postby allotmentboss » Tue Feb 26, 2008 8:38 pm

Ok, the water regulations confuse me.

My domestic hot water is provided 'on demand' by a combi boiler. I have no storage tank and the hot water is only supplied to the normal household taps; sink, bath, shower and so on. There are no outside taps, no slurry pits en route, or anything like that!

[b]Given this set up, do I need a double check (or non return) valve on the hot water pipe coming out of the boiler?[/b]

For reference, I already have:
(1) A double check valve on the filling loop for the central heating and
(2) Non-return valves on any mixer taps (such as the shower or bath mixer).

*************************
*** WHY I THINK I DON'T ***
Given that my main cold water supply pipe doesn't have a double check valve (and, as far as I can tell, doesn't need one) I don't understand why the hot water line needs one? Both hot and cold water are going through pretty much equivalent copper pipes in the house, so are equally "mucky" in the case of a pressure drop. In fact, the only difference between the two is the boiler, and fitting a valve before the boiler without an expansion vessel isn't sensible (or I guess safe!)
*************************

So, the question again: Do I need a non return/double check valve on the hot water outlet of my combi boiler?

MANY THANKS!
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Postby kbrownie » Tue Feb 26, 2008 10:53 pm

Hi,
No expert but I thought check valves are used on cold water supply to stop water siphoning back in to the drink water? I'm sure i'll be correct if wrong!
KB
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Postby ALDA » Tue Feb 26, 2008 11:01 pm

WHO OR WHAT SAYS IT DOES?

IT DOESN'T!
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Postby allotmentboss » Wed Feb 27, 2008 3:33 pm

Both,

Thanks for your answers. As to who or want says it does, the "you do" and "you do not" camps stack up as follows:

YOU DO:
(1) The man at B&Q who sounded authoritative but brobably just wanted me to buy one.
(2) A bloke in the office who "knows a bit about plumbing" (but works in IT, so you decide).

YOU DO NOT:
(1) Me. I'm no plumbing expert, but I'm working on the logic (as per my original post) that it wouldn't gain you anything.
(2) Both of you, by the sounds of things.

Once again, many thanks.

Phill
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Postby simpleton » Wed Feb 27, 2008 8:09 pm

no you dont. why would you??
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