Help! My unvented cyclinder keeps releasing hot steam

[dominoman]

I'm looking for some advice.

I have a unvented hot water cyclinder that feeds my flat, powered by an immersion heater. For the last few weeks it regularly releases steam via a small pressure release pipe. It'd got to the point where everything in that cloakroom is now permanently damp.

I've called a plumber out to service it and he said there was no problem but he turned down the thermostat a bit. Next day more water steaming out. I called him back and he replaced the pressure relief valve.

A day later and it is still leaking steam, though a bit less than before.

Does anyone have any ideas of what the problem could be. I've lost faith in the guy that has tried to fix it after paying him almost 400 quid now and not seeing any improvement.

Thanks very much for any ideas of what could be wrong.

 

[muggles]

You need to be G3 Registered to work on these. If it's releasing steam that does sound like an overheat problem and is quite a dangerous situation. Needs proper diagnosis from someone who actually knows what they're doing. Unfortunately it seems you've employed a chancer who doesn't. £400 to turn down a thermostat and replace a PRV is extortionate

 

[terryplumb]

You need a plumber with G3 qualification , to work on an unvented system. This is an additional qualification that not every plumber has. You stated your water is heated by immersion heater , but is it also heated by a boiler ? If not sure post a pic here of the hot water cylinder and pipework. In the meantime switch off the electric supply to immersion heater elements ,you may have two in the cylinder ,one low down one higher up. It sounds like your water is being heated to an abnormally high temperature ,and possibly have a problem with your expansion vessel as well. Any decent G3 qualified plumber can diagnose what the fault is ,once there ,quite quickly and can give you a quote to effect a repair.

 

[terryplumb]

Muggles ,you can type much quicker than me !! .