Have just discovered that my sealed (ie mains-pressure) HW cylinder (a
7-year-old Vaillant Vantage 200L) has developed a slow leak. Now for obvious reasons I'm not about to attept a repair myself, but would like to narrow down the problem a bit before I call in a pro, as this could clearly be hugely expensive to resolve.
The tank seems to sit within a snugly-fitted, grey plastic dish about 1" high (see photo in link below), and this dish is full of water and overflowing, and I can't see where the leak is. However, removing the immersion heater cover reveals a spongy seal (see photo), which is sodden, especially below the element. Now AFAICS the best case scenario is that the seal on the flange around the immersion heater has gone, which would be relatively straightforward to sort out; however I'm wondering whether it's possible that the wet sponge has just sucked up water by capillary action from the grey dish below?
I don't know anything about the anatomy of the tank inside its outer metal casing, and I wonder if anyone who does might be able to comment on the likely cause of the leak?
It's more likely that the leak is at one of the openings rather than on the cylinder itself.
Although damaging some sort of investigation is required (the tank will have to be replaced if it can't be repaired) and foam will possible to reinstate after.
Thanks Ed. That's certainly my hope as it would be megabucks to have the beast replaced. Not only are these cylinders of course very expensive, but our model is no longer available so lots of new pipework would be needed (never mind ripping my airing cupboard apart... :-( )
So do you reckon I should be taking a tin-opener or something to the outer metal casing, around the immersion heater flange, in order to visualise what's going on? ie, is trashing my tank like that that what an engineer would have to do now? I'm happy doing that level of work with a view to diagnosing the problem.
Well I'm glad I didn't get the angle grinder out, since having continued my investigations, I've found a tiny puddle on top of the tank, and discovered that the leak is from (what I think is?) a pressure regulation valve:
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hadn't noticed it before; but it's hidden away behind the thermostat housing and under a low shelf in the airing cupboard... anyway, evidently the leaked water is finding its way inside the outer casing of the tank on top, running down inside it and then exiting at the bottom - which did kind of wrong-foot me.
So... this looks a whole lot more straightforward to sort out. Does this device simply need unscrewing and replacing or is it serviceable?
The mains incoming (left) goes into the black valve this is a combined non return and pressure reduction valve. There are two black plastic plugs on the valve facing up and down (almost certainly R-1/4 threaded) which could take a pressure gauge. Although hidden by the blue knob the water carries on a 3.5bar into the valve with the blue knob (which might be all of a piece with the black valve?). The blue valve is the first over pressure unit (6 bar), it discharges into the pipe which exits bottom right. Hopefully it is less than 500 mm to the tundish (not shown). Above the blue knob valve is the white potable grade expansion vessel.
By the book you are meant to replace this stuff with the manufacturers correct replacements... What you do next very much depends on what's leaking.
Ah - I've just noticed the drip it on the Black valve. The black plastic _might_ be a dust cover (possible in two parts?) and underneath there might be a spindle gland which can be nipped up.
The the black knob valve is separate or can be separated from the blue-knob-valve then a generic pressure reduction valve set to 3.5 bar should work. Otherwise you better get the whole Vaillant part.
As you say, the leak is from the black valve. It seems shrouded in heavy-duty plastic, and does seem to be in two parts - you can see (on the link above) the join about an inch down from the front end: the water is leaking from here and also from around the disk on the front face where it says "SYR 3.5 bar". I can imagine a gland nut underneath as you say; however, although there is a tiny bit of 'give' in the tip it doesn't want to move. Can this by pried off with a bit of force? Or does it unscrew or something?
If it turns out that the whole black valve needs replacing, I note it has a hex at the base - can I simply unscrew it and swap in a like-for-like replacement? (sounds like that wouldn't need a G3 CORGI to do it?)
What have you got to lose - flooded house, not hot water for several days. Realistically though turn the cold feed off, depressure the cylinder (by opening a hW tap) and try your luck. A pressure reducing valve is not too difficult to buy off the shelf at a proper plumbing shop.
Have unscrewed the black valve casing at the hex. This was a shroud for a large spring which holds a piston/diaphragm arrangement in place, and at the base of which was a small nut. Didn't fancy undoing that at this stage, but if wiggled a bit it made hissing noises (presumably air bypassing the evidently failed diaphragm seal, while depressurised). The whole lot was very wet and corroded; presumably it should have been dry.
Did the rounds of the plumber's merchants - seems this valve is specific to Vaillant and I have to go with that model in order to avoid lots of pipework changes. Certainly hard to get hold of; only one merchant expressed any interest and they have to order it up. At least, the thing is available as a cartridge which fits inside my present valve housing, so no need for any pipework at all. Should be straightforward to swap in (when I can see the new component I'll be happier to dismantle the current one, which still needs to serve a few more days yet)!
What waa Ed saying above about "what have you got to lose?"
Just when I thought I'd got it sussed: when I replaced the valve shroud just now, the leak has got far worse - evidently I've moved some muck or something around the failed seal. Certainly far too bad to be able to catch the drips as before, so the water (H&C) is now off. I'm in deep do-do with SWMBO :-( and am clearly going to have to source the replacement valve tomorrow from God knows where. Presumably (he hopes) there'll be a way of isolating the hot side, so at least I can switch cold back on.
Meanwhile - does anyone know how the hell to get the innards of the valve out? I'm hoping I can clean it adequately enough to get it to seal again tonight at least....
do you mean isolating the cold feed to the cylinder?
at times like this when needing to do mods, Hep2O is your friend, even if only temporary mods.
I have a separate and different model PRV. It also has a hex on the moulded shroud. When I dismantled it once I noticed the spring and some inards. Unfortunately the innards refused to come out. After buying a generic replacement from BES I worked out that the innards wouldn't come out because the gauze mesh had fouled. Hope you have better luck.
Unvented cylinders need to come with a complete safety package. Not sure what the regs are regarding replacing the entire installed kit with generic but that may be an economic option compared with Vaillant spares, assuming they are actually obtainable.
Yes - found the relevant gate valve and done that now, so at least we have cold water back!
Here's the link to the photo of the innards I forgot to post earlier, if it helps anyone:
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I have a separate and different model PRV. It also has a hex on the moulded
Does sound similar...
Yep, talked to the plumber's merchant guy about this; I went for the Vaillant replacement innards (50 quid) because otherwise renewing the whole assembly would surely have been more expensive; not only that but also I'd definitely have needed a plumber (and I may yet! :-( )
suspect a wire gauze under the diaphram. If its not coming out even when encouraged by a pulse of pressure I suspect it may be fouled....
In the first photograph I thought the device was a composite device. In the second photo it appears the PRV is a separate part. That makes replacement a bit easier. You could remove the PRV by pipeslicing the inlet pipe and unscrewing the PRV from the safety valve (though it looks as if the bl**dy spindle might foul the pressure vessel). You will see the gauze through the inlet and outlet ports.
have a look at BES. I used p/n 11345 but there are others. Tip - search using "sealed" not "pressure reducing valve". BES - great range but cr*p online catalogue.
I was expecting that either he would replace the entire valve or he would replace the valve with an equivalent generic item.
Looks like you would have to unscrew the vessel to allow the valve to unscrew. I suspect that the whole gubbins including the releif valve are only held by three compression joints. In which case I'd get the whole lot out where it can be worked on more easily.
Either the genric valve is a bit longer or shorter than the existing; thus requiring at worst a short extra lentgth of 22 copper and a coupling.
What a week... Finally got the hot water back yesterday, after FOUR days without. Rang the plumber first thing Tuesday morning - said he'd almost certainly be round later that day, but if not then definitely Wednesday. Not a peep out of him so I ring again Wednesday morning: "really sorry, got held up out of town, not back till 8pm but I'll definitely be round later today... Yes, absolutely certain... Honest mate, I promise you..." Guaranteed... 100%... Promise."
And guess what - nothing. Bastard [*]. So first thing Thursday morning I phone another plumber - one of those posh expensive sort with receptionists answering the phone and fleets of branded vans :-( . Two hrs later I have someone round confirming the diagnosis - the new part is duly ordered. Minor panic when it looked as if it wouldn't arrive until after the bank holiday - but it did, and he came back yesterday (Friday) to fit it. Never heard from plumber #1 again.
The whole valve plus housing was replaced with an original - seemed most cost-effective as it avoided any pipework... I'm sure I could have done it but as I know zip about pressure safety systems on unvented tanks, I wasn't comfortable in doing so. And as regards dismantling the faulty valve in situ... not a chance. I had a play with the old valve this morning and eventually got the innards out using a club hammer and drift from the back, and knackering the remains of the thing in the process. Evidently it should have simply pulled out, but it was totally seized up.
David (now hoping to be allowed back in the marital bed by the end of the bank holiday...)
[*]WTF is it with so many tradesmen these days? Why couldn't he have said 'sorry, too busy', or 'no can do'; but not only did this guy let me down he CBA even to give me a ring to let me know he couldn't come; costing me an extra 2 days with now HW. The bizarre thing with this plumber is that he fitted a boiler for me elsewhere last week (first time he's worked for me). Did a good job and as he left I pretty much promised him the job of fitting a complete CH system later in the year, which he seemed pleased about. And then he does this to me, so has 100% guaranteed that he's lost that job. (Furthermore he's only just sent me the invoice for last week, so maybe I should sit on that for a bit... "Honest mate, promise you the cheque's in the post...!"
I did try that; but couldn't find for certain exactly what model the valve was and as I really don't understand exactly how it works or what it does, I wasn't about to risk compromising things (or ordering up the incorrect, expensive part! If I'd had a "Haynes manual" or even a user guide beyond Vaillant's pathetic two-page offering I might have been more confident.
Just over 100 for the valve, including next-day delivery. Not sure about the labour side - waiting for the bill: frankly I didn't dare ask, which isn't like me...!
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