Is this an isolation valve?
Alan
valve which is part of the top-up for the CH system.
The top-up is a simple flexible connection with an obvious isolation valve
with handle on one side and something which looks like an isolation valve
but has a hex nut where I would expect a slotted screwdriver fitting or a
handle.
A quick check shows that the hex nut will go through more than a quarter
turn and is currently turned as far clockwise as it will go.
I'm wary of turning it too far anti-clockwise just in case it's going to
come unscrewed, fall out and coverthe floor in water
Here's a photo of the set up
http://tinyurl.com/2az5hwt
The offending item is on the left - here's a close up photo
http://tinyurl.com/28cnbpx
I've had a quick look through various web-sites but I've not come across an
isolating valve looking like this.
Can someone enlighten me please - if I turn the nut fully anti-clockwise
will it shut off the system or will it just fall out?
Alan
--
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ARWadsworth
It's a double check valve.
http://www.screwfix.com/prods/96336/
I would not turn the nut fully anti-clockwise.
--
Adam
Alan
So IIUC, this is what I think of as a one-way valve so I can simply turn off
the water supply and disconnect the leaking isolation valve and there won't
be a back-flow of water from the double chweck valve end?
Andy Wade
> So IIUC, this is what I think of as a one-way valve so I can simply turn off
> the water supply and disconnect the leaking isolation valve and there won't
> be a back-flow of water from the double chweck valve end?
Correct. You might find this helpful:
http://www.makewrite.demon.co.uk/SealedCH.html
--
Andy
Andrew Gabriel
The nut is designed to allow testing that both of the double check
valves are working - there's one either side of it. It should be left
tighened up normally, and should not leak.
The braided hose should not be left in place except when you're topping
up the heating system. With the hose removed, no water should leak
back out of that valve, and if you do undo that nut, no water should
leak out of that either (save for an initial drip because the cavity
it goes into will contain static water, but it shouldn't carry on
dripping indefinitely). If the double check valve leaks from either
point, it should be replaced. This can probably wait until you are next
having the heating serviced - it's probably not an emergency unless
it starts leaking fast. With the hose in place, it's not possible
to say if the valve has failed of not, as it may be preventing enough
pressure difference to fully shut off the double check valve.
IME, the guts of these valves are destroyed if they ever get frozen.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
Alan
Thanks,
John Rumm
The double check valve lets water flow into the CH system from the
mains, but prevents its return. So you could remove the flexible
connection, and with the the tap closed on the right, no water will flow
from either side.
Obviously you can't remove either valve from the fixed piping without
water escaping since the valve is all that is holding it back.
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
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ARWadsworth
But he can turn off the mains cold water and then remove/replace the leaking
isolation valve.
--
Adam
John Rumm
Not sure which isolation valve you mean? In the original photo I can
only see two valves; the tap on the right and the double check on the
left unless I have missed something? You won't be able to take either of
those off the pipework without getting wet! The only bit you can safely
disconnect is the braided flexy connection.
Alan
The tap on the right (with the handle) is the one I want to change. Now I'm
told that the other (which I didn't recognise) is a non-return valve I can
just shut off the water and disconnect it without the entire CH system
draining onto the floor ;-)
Thanks to all
ARWadsworth
The valve on the right (I assumed the one with the plastic tray underneath
it catching the drips needed replacing). However the OP could have moved the
tray for the photo!
Once the mains water stop tap is turned off, there is no reason why it
cannot be removed and replaced (other than the standing water in the
pipework if the cold taps in the house are not opened up)
The OP certainly cannot remove the double check valve without draining his
radiators.
--
Adam
John Rumm
Yup with all the focus on the double check valve, I assumed that was the
one he wasted to replace.
> Once the mains water stop tap is turned off, there is no reason why it
> cannot be removed and replaced (other than the standing water in the
> pipework if the cold taps in the house are not opened up)
Indeed - the key step being turning off the water! It sounded from
earlier discussion like he wanted to swap out the tap without doing that.
> The OP certainly cannot remove the double check valve without draining his
> radiators.
Well once you have dropped the pressure a bit by draining a couple of
litres, you can swap one tap for another with a quick thumb over the end
shufty. Usually don't spill more than a cup full if you are quick.
John Rumm
Yup, disconnect the flexy hose. The double check on the left will keep
the water in the CH system. (you may spill half a cup out of the hose!)
The valve with the knob you can change once you have turned off the
mains cold water. Again if you drop the pressure a bit at a tap, and
then endure the other taps are off, you can do a quick swap like for
like without draining everything down.
Alan
Went to try changing the isolation valve (tap) - turned off the mains,
checked no flow through taps and disconnected the flexible hose at the tap
end - water poured out from the flexy hose :o
Fortunately I was paranoid enough to have been prepared (with plasic sheet
and bowl) so no harm done.
Looks like the double check valve is also naff so now it's down to draining
the system and replacing both valves :(
ARWadsworth
Did you say something that rhymed with Clucking Bell when the water poured
out?
--
Adam
fred
>>
>Went to try changing the isolation valve (tap) - turned off the mains,
>checked no flow through taps and disconnected the flexible hose at the tap
>end - water poured out from the flexy hose :o
>
>Fortunately I was paranoid enough to have been prepared (with plasic sheet
>and bowl) so no harm done.
>
>Looks like the double check valve is also naff so now it's down to draining
>the system and replacing both valves :(
>
To avoid this sort of problem my system has a 1/4 turn isolating valve
on both the mains side and the C/H side.
Also, to make it easier to drain down the system and to inject
inhibitor, I have an open port (via valve) on the system side and the
check valve on the mains side (flipped to correct the orientation).
As you're draining down anyway this may be a sensible change to
incorporate.
If you fancy a bigger chore, it may be time to shift the filling point,
above that rad isn't the most inconspicuous spot.
--
fred
FIVE TV's superbright logo - not the DOG's, it's bollocks
John Rumm
Deep joy!
> Fortunately I was paranoid enough to have been prepared (with plasic sheet
> and bowl) so no harm done.
>
> Looks like the double check valve is also naff so now it's down to draining
> the system and replacing both valves :(
If you are feeling brave, leave the flexy connected at both ends, and
undo to union nut for the double check valve, while keeping it pushed
against its stub of pipe with the other hand. Once the nut is free,
quickly swap the DC valve for a new one[1], and do the nut up again. As
long as the CH is off, and you have bled a litre of water out of a rad
somewhere, you won't lose much more.
Just make sure you have the replacement bits easily to hand and in the
right state to use!
[1] Pull valve off, thumb over pipe end, pick up new valve and repeat.
Push valve against pipe stub while tightening union nut.
Alan
Actually it was more like Go Hit! :)
--
Alan
email ~= s/nospam//
Andrew Gabriel
John Rumm <see.my.s...@nowhere.null> writes:
>
> If you are feeling brave, leave the flexy connected at both ends, and
> undo to union nut for the double check valve, while keeping it pushed
> against its stub of pipe with the other hand. Once the nut is free,
> quickly swap the DC valve for a new one[1], and do the nut up again. As
> long as the CH is off, and you have bled a litre of water out of a rad
> somewhere, you won't lose much more.
Need to drain enough so pressure guage shows zero.
> Just make sure you have the replacement bits easily to hand and in the
> right state to use!
>
> [1] Pull valve off, thumb over pipe end, pick up new valve and repeat.
> Push valve against pipe stub while tightening union nut.
--
Andrew Gabriel
fred <n...@for.mail> writes:
> If you fancy a bigger chore, it may be time to shift the filling point,
> above that rad isn't the most inconspicuous spot.
Try to keep it so you are within line-of-sight of the pressure guage
whilst filling system. Another option would be to add another
pressure guage at the filling point.
John Rumm
> In article<S9SdndaK35JGmjPR...@brightview.co.uk>,
> John Rumm<see.my.s...@nowhere.null> writes:
>>
>> If you are feeling brave, leave the flexy connected at both ends, and
>> undo to union nut for the double check valve, while keeping it pushed
>> against its stub of pipe with the other hand. Once the nut is free,
>> quickly swap the DC valve for a new one[1], and do the nut up again. As
>> long as the CH is off, and you have bled a litre of water out of a rad
>> somewhere, you won't lose much more.
>
> Need to drain enough so pressure guage shows zero.
Well near enough - if the gauge is downstairs then just the weight of
water in the upstairs bit of the circuit will register a little bit
usually.