Hi, I need some advice. I came back to my house a couple of weeks ago to hear it raining hot water through my kitchen ceiling. The expansion vessel on the unvented hot water system had split open (apparently pretty violently) and was gushing steam and water into my airing cupboard. Luckily no one was under the water or they might not be here now and the damage was not too bad (must only have happened 4 or 5 minutes before my return). We had the tank recently moved by the builders of our extension and there seem to have been a couple of issues: * The temperature and pressure relief valve had no tundish fitted and was fed into a 15mm pipe which ran through some convoluted bends into a soil pipe in the airing cupboard * The pressure relief valve was at low level and had a pipe leading upwards to join the 15mm pipe mentioned above * The pressure relief valve from the central heating system also fed into the same 15 mm pipe via a long (1m horizontal) 15mm pipe I now know that this breaks building and water regulations and that the installer was probably not certified. The things I would like to know are: * From the above, does it seem likely that the incorrectly installed safety systems caused the explosion? * Any suggestions on the best way to proceed to prevent a reoccurrence? Who can I trust to fix the system? * Who should be inspecting these things? Should I get building control from the local council? All advice gratefully received. Thanks.
I now know that this breaks building and water regulations and that the installer was probably not certified. This is illegal - inform you local BCO and trading standards. Get a decent plumber who has his UVC certificate to check it all over. Until you have turn the heating and hot water off for your own safety.
sounds like they was right cowboys stand by for walter i bet he carnt wait to reply about this make sure u have turned all off water and electric and heating to it
Photographs and a video then straight to HSE, best responce if someone was hurt, but still plenty of potential!
I don't think it'll be Walter. It sounds like someone has buggered up the safety devices, and it still hasn't brought the house down or killed anyone, just leaked a bit.
none of the faults mentioned by the op would cause the expansion vessel to explode, switch it off as already said until you can get someone qualified to check it over.
Re: the damage to the expansion vessel, the metal is ripped for around 270 degrees underneath, nearly where the vessel reches its maximum diameter and the top of the vessel is bent back at an angle. Gap is about 5cm at widest point. I reckon it must have been going some to bend it in that way.
none of the faults mentioned by the op would cause the expansion vessel to explode, I wasn't thinking they would, but given the description so far it's anyones guess what else these 'builders' have done. Blocked the D2 relief pipe??? Left the cold water combination valve off the supply???
I quite agree mantor,but its a very unusual for an expansion vessel to explode, I wonder if the builders have put a red ex vessel on and its rusted.
I dont think anyone with that catastrophe would come on Screwfix Forum looking for answers,its HSE stuff,insurance,public liability and probably but hopefully??? A wind up.
Total bodge job incorrect installation,report the builders to building control.Because the person who resited the cylinder & piped it up has not got a clue obviously not certified & building control should have been notified.
The exp vessel is your last line of defence, after this its game over with the tank and Walter Systems hits paydirt!! Something is blocked somewhere.
A wind-up. A typical unvented (e.g. megaflo) will have a 3 bar reducing valve on the cold inlet and an 8 bar PRV on the same, so that the cold feed is never more than 8 bar (and of course mains is usually much less). The cylinder and exp vessel will be rated to 10 bar at least, and there is a factory fitted 10bar/90c TPRV, alongside safety cut-out stat. So, if heated by electricity..... - the TPRV and the safety cut-out will have to have failed. and even then the immersion wouldn't deliver enough energy to blow the cyl If heated by gas...... - the gas boiler would have to have heated the water to over 100c, the thermal cut out must have failed, the TPRV has failed Exp vessel has been dropped, but even then I don't believe that it would blow like that. What people fail to realise is the temperature required to "boil" pressurised water. It is much higher than 100c, so I'm sure someone will tell me how so much energy is injected into the system!
The cylinder will not be a Megaflo, in this case it has a internal diaphram no external pressure vessel.
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