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Can anyone help me out and explain what the smaller white vessel is to the left of my hw tank (enlarged in the second photo)?
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Reason I ask is that it's had a slow leak for ages - you can see some of the water beading on the screws in the photo. Wondering how to tackle it so I thought I'd start by asking what the small tank is?
Also, the white pipe that I've just propped up with some wood on a paint tin is also leaking (slowly) where it meets the black fitting. The joint is not under any pressure, so is it just a case of getting it horizontal?
Thanks for any advice.
It is an expansion vessel for your unvented system.
You should not touch it. Only certified plumbers may work on unvented systems.
The white pipe looks like the outlet for the pressure relief valve. Although plastic pipes are permitted for he discharge pipe, they need to be tested for 110degC. Id get that double checked if I were you.
So that black "fitting" underneath the tundish - is it basically an elbow connecting the tundish outlet to the white plastic discharge pipe? or is it a T connection where the white pipe is flowing into it and then past the back of the tank?
If the former, the white pipe shouldnt have a leak at all - that would suggest that the pressure relief valve is dribbling (it does happen quite easily, but ought to be fixed by servicing the valve seat and refitting, but again that ought to be done by a qualified plumber).
If the latter, Im not sure it's approved to have the discharge join another waste outlet at all.
Ty Stoner. The black thing is a T connection that goes past the back of the tank.
The central heating is working fine, it's just this damp patch in the cellar caused by the slow leak that I'd like to fix. Guess I could start by tightening the screws and if that makes no diff as a plumber to look at it.
The pressure vessel controls the expansion pressure in your cylinder and prevents it exploding. I would guess that the diaphragm inside had ruptured and the whole thing needs replacing, should cost around 30 quid from screwfix etc. I slightly dripping relief valve when the tank is hot would confirm a knackered expansion vessel. I've changed a few of that particular brand after add little as a year
It looks to me like an inexperienced plumber had fitted it. As stoner has mentioned, the discharge pipework is quite wrong and could do with sorting at the same time
hmm. So where does the white pipe come from?
And once it's gone through the black fitting, what kind of pipe is it on the outlfow side? It's supposed to discharge safely (usually outside).
If the CH is working fine, then it's not a pressing problem. It would suggest that the membrane in the expansion vessel is intact.
EDIT: (TFM - if the rubber was shot, then the system would leave via the pressure relief valve each cycle) Unless, of course, we are assuming that the pressure relief valve is operating while GarryLager isnt watching?
It wouldn't release fully unless the pressure was excessively high, they usually just weep almost constantly.that only indicates a failed diaphragm or low pressure in the cylinder. Either way it definitely shouldn't leak on that seal and they're usually not serviceable parts
Discharge pipework does not comply with regulations.
Vessel will need replacing, they are not serviceable, unless recharging the pressure. Not sure that it will be £30 for a potable water expansion vessel though.
aha. gotcha. I was thinking low pressure as opposed to failure, but then it hasnt been recharged has it.
Out of interest, is the rubber inside the expansion vessel a "balloon" or fixed sheet across at half way?
[url= http://en.wikipedia.org/wiki/Hydraulic_accumulator ]Its a hydraulic accumulator[/url] which are used to smooth out pressure fluctuations.
Are you sure? They certainly feel like an empty can to me