Faulty Relief Valve on Bosch Combi Boiler?
Discussion
Evening all,
I've only been in this house for 3 months or so. The boiler was great until the Xmas period, but since then it's been losing pressure every couple of days. I've been opening the inlet to top it up to compensate.
But tonight I noticed I was only getting hot water for 30 seconds at a time, then cold. Even running the hot tap beyond this the boiler wasn't firing. So I took a trip out to the garage to investigate and immediately noticed water coming out of this valve at the top. Current pressure is back down to 1psi (hot) and it's still dripping. There shouldn't be water coming out of there based on my limited knowledge. Does this mean the "bladder??" inside is bust? Yes I've been googling, although do remember this from my old system.
p.s what are the two grey inlets for on the top centre of the boiler?
I've only been in this house for 3 months or so. The boiler was great until the Xmas period, but since then it's been losing pressure every couple of days. I've been opening the inlet to top it up to compensate.
But tonight I noticed I was only getting hot water for 30 seconds at a time, then cold. Even running the hot tap beyond this the boiler wasn't firing. So I took a trip out to the garage to investigate and immediately noticed water coming out of this valve at the top. Current pressure is back down to 1psi (hot) and it's still dripping. There shouldn't be water coming out of there based on my limited knowledge. Does this mean the "bladder??" inside is bust? Yes I've been googling, although do remember this from my old system.
p.s what are the two grey inlets for on the top centre of the boiler?
The part in question is not a 'relief valve' it is actually an automatic air vent which will release any air in the boiler and is then suppose to seal up.
Ideally, yours needs replacing. They are cheap. You can often close them off by screwing the little cap down. This might stop the 'leak' but of course it won't act as an auto air vent any longer. I find many of them closed because they leak a little.
It is not an indication that your expansion as failed. That doesn't mean it hasn't, or that it doesn't need pumping up.
The system pressure should ideally be set to around 1 bar cold, if it shoots right up much beyond 2 bar when all your rads get hot then the expansion vessel needs attention.
The 2 grey inlets are for flue gas analysis used normally during maintenance/servicing to confirm good combustion and healthy flue.
Ideally, yours needs replacing. They are cheap. You can often close them off by screwing the little cap down. This might stop the 'leak' but of course it won't act as an auto air vent any longer. I find many of them closed because they leak a little.
It is not an indication that your expansion as failed. That doesn't mean it hasn't, or that it doesn't need pumping up.
The system pressure should ideally be set to around 1 bar cold, if it shoots right up much beyond 2 bar when all your rads get hot then the expansion vessel needs attention.
The 2 grey inlets are for flue gas analysis used normally during maintenance/servicing to confirm good combustion and healthy flue.
Thanks for the advice.
I'll put the valve cap back on, perhaps with some plumbers tape and set the pressure to 1 bar cold tomorrow night before firing it up and see how it goes.
I did see it peak at almost 3 bar tonight which worried me, but I did probably top it up to 1.5 bar cold before firing it up. .
Will report back. Thanks again.
I'll put the valve cap back on, perhaps with some plumbers tape and set the pressure to 1 bar cold tomorrow night before firing it up and see how it goes.
I did see it peak at almost 3 bar tonight which worried me, but I did probably top it up to 1.5 bar cold before firing it up. .
Will report back. Thanks again.
Edited by scz4 on Tuesday 14th January 22:50
scz4 said:
Thanks for the advice.
I'll put the valve cap back on, perhaps with some plumbers tape and set the pressure to 1 bar cold tomorrow night before firing it up and see how it goes.
I did see it peak at almost 3 bar tonight which worried me, but I did probably top it up to 1.5 bar cold before firing it up. .
Will report back. Thanks again.
Sounds like the exp.vessel is pretty flat TBH. Even with a cold 1.5bar it should not rise to much more than 2bar with a healthy charge.I'll put the valve cap back on, perhaps with some plumbers tape and set the pressure to 1 bar cold tomorrow night before firing it up and see how it goes.
I did see it peak at almost 3 bar tonight which worried me, but I did probably top it up to 1.5 bar cold before firing it up. .
Will report back. Thanks again.
Edited by scz4 on Tuesday 14th January 22:50
Maybe time to have the boiler checked over.
If the time is not right to get it checked out, close the AAV with cap. Fill to 1 bar cold only. Turn down the left hand temp knob to say round 3. This will reduce the level of expansion and might stop you losing pressure - some water might have been dripping from the PRV (overflow) pipe. Usually a curled pipe outside. Obviously the radiators won't get as hot.
Well there's no more water leaking from that valve, was dry this morning. However, something more serious is happening.
I had no hot water this morning upstairs, but did downstairs, probably because the pressure was almost 0 bar this morning and a big pool of water under the boiler which wasn't there when I turned it off last night. Pressure was also 1 by the time it turned off last night, so it's lost pressure over night when turned off.
Time to call a plumber and get the credit card out
I had no hot water this morning upstairs, but did downstairs, probably because the pressure was almost 0 bar this morning and a big pool of water under the boiler which wasn't there when I turned it off last night. Pressure was also 1 by the time it turned off last night, so it's lost pressure over night when turned off.
Time to call a plumber and get the credit card out
I had a very similar problem with a Vailant combi three months after buying the bloody house. In my case from memory the heat exchanger had also failed and was leaking along with the same valve thing as yours and then the pressure relief also failed so that it wouldn't "relieve" which turned the boiler into a watery time bomb. Makes you think about all the people who have them in lofts as we wouldn't have known about it until something popped without noticing the gauge getting up to 4 bar!
From memory I was quoted about £600 to fix it which included some other stuff like a completely mullered filling loop. I vaguely recall it needed to come off the wall for some reason as well which made it a lot more expensive. Ended up replacing it as it was 17 years old anyway and to be honest it was actually worth the money just for the piece of mind and having a warranty.
From memory I was quoted about £600 to fix it which included some other stuff like a completely mullered filling loop. I vaguely recall it needed to come off the wall for some reason as well which made it a lot more expensive. Ended up replacing it as it was 17 years old anyway and to be honest it was actually worth the money just for the piece of mind and having a warranty.
Trustmeimadoctor said:
Handy link. Are they quite compettiive. It seems to be recommending me two boilers:
Worcester Bosch Greenstar 8000 Life 45kW @ £3300 fitted
or
Worcester Bosch Greenstar 8000 Life 50kW @ £3820 fitted.
Same heating output rating, only difference is the hot water flow rate.
Paid £2500ish. Not the cheapest and in the South East but guy who did it was a recommendation and he did a lovely neat job. It's a Glow Worm something or other (made by Vailant apparently) with a ten year warranty and it just works and so never have to think about it.
Probably paid too much but gives you a ballpark figure.
Probably paid too much but gives you a ballpark figure.
scz4 said:
Handy link. Are they quite compettiive.
It seems to be recommending me two boilers:
Worcester Bosch Greenstar 8000 Life 45kW @ £3300 fitted
or
Worcester Bosch Greenstar 8000 Life 50kW @ £3820 fitted.
Same heating output rating, only difference is the hot water flow rate.
I'm sure your boiler is perfectly fixable. All the parts are still available. However, I think I'd be inclined to replace it with a new one at 17 years old. It seems to be recommending me two boilers:
Worcester Bosch Greenstar 8000 Life 45kW @ £3300 fitted
or
Worcester Bosch Greenstar 8000 Life 50kW @ £3820 fitted.
Same heating output rating, only difference is the hot water flow rate.
Those prices are on the high side IMO. They are very powerful boilers, I don't think necessary personally.
FWIW just get a free quote from BG. You might just be surprised. If nothing else it gets a person out to pick their brains and gives another comparison. Nothing to lose.
Hopefully it's fixable, just need a plumber to actually call back. Got a Worcester\Bosch "representative" coming out to do a quote\survey tomorrow afternoon
Tonight I'm getting no hot water other than what seems to be in the system. So I initially get hot water for 30 seconds (assuming central heating has been on) and can see the flow temperature clocking down to 25 degrees when I then get cold water. The burner never comes on when the tap is open. A minute after the tap is closed the central heating kicks in again.
Tonight I'm getting no hot water other than what seems to be in the system. So I initially get hot water for 30 seconds (assuming central heating has been on) and can see the flow temperature clocking down to 25 degrees when I then get cold water. The burner never comes on when the tap is open. A minute after the tap is closed the central heating kicks in again.
Diverter valve
If your central heating is functioning perfectly but there is no hot water coming from your shower or taps, it is likely an issue with the diverter valve. This valve allows a combi boiler to switch between heating your radiators and your hot water, so when you turn on your hot tap, the diverter valve opens and sends hot water to the tap. If you are experiencing this problem then the diverter valve may be faulty, or it may be stuck in the central heating position.
If your central heating is functioning perfectly but there is no hot water coming from your shower or taps, it is likely an issue with the diverter valve. This valve allows a combi boiler to switch between heating your radiators and your hot water, so when you turn on your hot tap, the diverter valve opens and sends hot water to the tap. If you are experiencing this problem then the diverter valve may be faulty, or it may be stuck in the central heating position.
scz4 said:
Diverter valve
If your central heating is functioning perfectly but there is no hot water coming from your shower or taps, it is likely an issue with the diverter valve. This valve allows a combi boiler to switch between heating your radiators and your hot water, so when you turn on your hot tap, the diverter valve opens and sends hot water to the tap. If you are experiencing this problem then the diverter valve may be faulty, or it may be stuck in the central heating position.
Did you read he had a pond underneath the boiler?? If your central heating is functioning perfectly but there is no hot water coming from your shower or taps, it is likely an issue with the diverter valve. This valve allows a combi boiler to switch between heating your radiators and your hot water, so when you turn on your hot tap, the diverter valve opens and sends hot water to the tap. If you are experiencing this problem then the diverter valve may be faulty, or it may be stuck in the central heating position.
Thoughts I'd update this thread.. I received quotes for a new boiler, however one plumber let it slip that Worcester\Bosch do a fixed price repair for £275 even on a 17\18 year old boiler, so booked in for tomorrow. https://www.worcester-bosch.co.uk/support/boiler-r...
The leak has stopped after tightening that valve cap up, but still shouldn't be water coming out of there, still no hot water though.
The leak has stopped after tightening that valve cap up, but still shouldn't be water coming out of there, still no hot water though.
scz4 said:
Thoughts I'd update this thread.. I received quotes for a new boiler, however one plumber let it slip that Worcester\Bosch do a fixed price repair for £275 even on a 17\18 year old boiler, so booked in for tomorrow. https://www.worcester-bosch.co.uk/support/boiler-r...
The leak has stopped after tightening that valve cap up, but still shouldn't be water coming out of there, still no hot water though.
The leak has stopped after tightening that valve cap up, but still shouldn't be water coming out of there, still no hot water though.
No, water shouldn't be coming out of the AAV. It has a float type mechanism inside that seals the outlet up once air as been vented. It needs replacing ideally rather than being left closed.
The no hot water issue could simply be a faulty flow switch. And as said before the expansion vessel is probably flat. I think it'll be a straight forward job for WB when they visit you.
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