Temporarily turning off hot water in a combination boiler system?

Adam Funk

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Nov 25, 2016, 1:30:05 PM11/25/16

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I need to fix a hot tap in a sink in a relative's house (either clean
out & replace the washer, or perhaps replace the tap) --- that's
fine. But there's no service valve for this tap, and she has a
combination boiler.

What's the correct procedure for turning off the flow of hot water
from the boiler in order to cut the pipe and put a service valve in?
Should there be a valve somewhere downstream of the boiler, or do I
turn off the main stopcock coming in?

Thanks.

Scott M

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Nov 25, 2016, 1:32:09 PM11/25/16

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Adam Funk wrote:

> What's the correct procedure for turning off the flow of hot water
> from the boiler in order to cut the pipe and put a service valve in?
> Should there be a valve somewhere downstream of the boiler, or do I
> turn off the main stopcock coming in?

There's no "correct" procedure. Just prevent the water flowing!

There's usually a valve on the cold water inlet of most combis.
Otherwise just turn off the cold on the stopcock.

No need to turn the heating off either.

--
Scott

Where are we going and why am I in this handbasket?

Tim Watts

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Nov 25, 2016, 1:32:41 PM11/25/16

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On 25/11/16 18:20, Adam Funk wrote:
> I need to fix a hot tap in a sink in a relative's house (either clean
> out & replace the washer, or perhaps replace the tap) --- that's
> fine. But there's no service valve for this tap, and she has a
> combination boiler.
>
> What's the correct procedure for turning off the flow of hot water
> from the boiler in order to cut the pipe and put a service valve in?
> Should there be a valve somewhere downstream of the boiler,

Unless there is a ballvalve isolator inline with the tap, there is no
standard valving - it's always house dependent.

> or do I
> turn off the main stopcock coming in?

Quite possibly.

> Thanks.
>

newshound

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Nov 26, 2016, 2:20:16 PM11/26/16

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Don't Combis normally have a tap on the DHW outlet? That said, turning
off the main at the inlet (or the stop tap) is all that is needed. It's
perfectly safe to leave the CH running with the mains stop tap turned off.

Adam Funk

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Nov 29, 2016, 6:00:05 AM11/29/16

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Thanks, everybody. I do remember that her boiler has separate
controls for turning the CH & hot water on & off.

NY

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Nov 29, 2016, 6:28:00 AM11/29/16

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"Adam Funk" <a24...@ducksburg.com> wrote in message
news:dk30hdx...@news.ducksburg.com...

Er, are you talking about turning off the heating aspect of the boiler or
turning off the water supply? I thought you were talking about replacing a
tap washer, which mean tuning off the water supply to that tap (either by
closing a stop vale of by turning off the rising main). Turning off the hot
water control at the boiler would simply ensure the water to the tap was
cold rather than hot - it wouldn't turn off the water flow itself. Maybe
I've misunderstood your phrase "her boiler has separate controls for turning
the CH & hot water on & off" - maybe you are referring to a tap rather than
a control switch. Or maybe your system has motorised stop valves, which
*would* mean that when HW is turned off at the boiler controller, water flow
was turned off.

Adam Funk

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Nov 29, 2016, 2:00:06 PM11/29/16

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What I mean is this (just to clear):

1. turn the boiler control for hot water off;
2. turn off the main stopcock;
3. cut into the pipes and add service valves for the hot & cold taps
(might as well, in case the cold one goes next);
4. turn the main water back on & check that the service valves don't
leak;
5. turn the boiler control for hot water back on (so she can use hot
water at the other sinks);
6. fix the dodgy tap as necessary, reconnect, & turn the new service
valves on.

Roger Hayter

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Nov 29, 2016, 3:56:17 PM11/29/16

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I assume the CH can't work with the hot water control turned off? This
seems to be true of all the combi boiler designs I've seen, though I am
happy to be proved ignorant.

--

Roger Hayter

newshound

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Nov 29, 2016, 4:10:41 PM11/29/16

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Certainly my experience. Forget items 1 and 5.

Adam Funk

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Dec 13, 2016, 5:30:05 AM12/13/16

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On 2016-11-29, Roger Hayter wrote:

> Adam Funk <a24...@ducksburg.com> wrote:
>
>> On 2016-11-29, NY wrote:
>>
>> > "Adam Funk" <a24...@ducksburg.com> wrote in message
>> > news:dk30hdx...@news.ducksburg.com...
>> >> On 2016-11-26, newshound wrote:
>>
>> >>> Don't Combis normally have a tap on the DHW outlet? That said, turning
>> >>> off the main at the inlet (or the stop tap) is all that is needed. It's
>> >>> perfectly safe to leave the CH running with the mains stop tap turned
>> >>> off.
>> >>
>> >> Thanks, everybody. I do remember that her boiler has separate
>> >> controls for turning the CH & hot water on & off.

I was wrong about that --- the HW control knob ranges from low to
high, not including off.

>> What I mean is this (just to clear):
>>
>> 1. turn the boiler control for hot water off;
>> 2. turn off the main stopcock;
>> 3. cut into the pipes and add service valves for the hot & cold taps
>> (might as well, in case the cold one goes next);
>> 4. turn the main water back on & check that the service valves don't
>> leak;
>> 5. turn the boiler control for hot water back on (so she can use hot
>> water at the other sinks);
>> 6. fix the dodgy tap as necessary, reconnect, & turn the new service
>> valves on.
>
> I assume the CH can't work with the hot water control turned off? This
> seems to be true of all the combi boiler designs I've seen, though I am
> happy to be proved ignorant.

AFAICT the CH did keep running with the water supply (main stopcock)
turned off; but I was wrong about being able to turn the HW function
off at the boiler (without turning the boiler completely off).