Gravity fed CH expansion tank full of hot water

31 Oct 2003
Reaction score
United Kingdom
everything seems to be working fine , have hot water although very hot , ch all ok , but i get a splashing noise comming from the loft where the tank and expansion tank is , when i went up the other day to check there was scolding hot water going into the expansion tank from the pipe that come in from the top , the expansion tank has no cover on and the hot water is causing alot of condensation over roof and dripping down through the ceiling... could this be the thermostat in the boiler not operating correctly so turning on gas valve and heating more water then when it gets upstairs there noweher for it to go so it puts it in the expansion tank?
Thanks in advance for any help.
Sponsored Links
Try & turn the boiler stat down,then see what happen,sounds like hot water overheating too quickly or pumping over
i have had the stat on min for last few weeks and still does it.. i taken out stat today and check with meter seems to be opening and closing with different temps of water ok, unless it has an intermittant fault?? dont wanna go out and buy new one if this is not the cause. thanks
Also check your hot cylinder stat as you said you're getting very hot water and what I'm thinking is that your boiler is continuing to heat the hot water & the water circulation is expanding water over to your f & e tank
Sponsored Links
exact same thing happened to my system (expansion tank thinking it was a kettle) turned out to be a blockage near to the heating pump.
Everything is not working fine. Whatever controls the temperature on your boiler, thermostat or thermocouple, is defective I suspect. If you can't sort it very soon, get someone in to fix it. This a potentially dangerous situation. Alright, it was a combination of exceptional circumstances, but someone has been killed by this. So in the meantime switch off your boiler.
yesturday i drained down system and , i noticed a drain of valve at side of boiler was leaking a little , replaced that refilled and have set thermostat to min on boiler ( there is no stsat on the tank.) , hw seems to be ok now , not mad hot and there are no noises comming from loft , checked expansion tank and it is full of cold watrer.. hope it lasts a few more weeks i`m have a combi installed so goodbye to the tank and expansion tank..
Thanks for everyones help.
Could I ask, what are your reasons for a combi?
1st to get rid of tanks in loft to give extra room.
2nd for instant hot water on denmand
3rd , boiler at mo over hangs kitchen window a little and we are to fit a new kitchen and hopefully will be able to replace boiler with one thats not quite as wide.

while i on what are the regs regarding the space around the wall vented flue , the next door neigbour had an extension built years ago b4 we moved in but i think it was put up after the CH was installed in my house, the extension comes within 6" of the flue. will a corgi regester installer be able to fit new boiler in this location or will it have to be moved?

It may be possible to put the boiler in the same place, but the flue terminal will have to move. Clearances are 300mm from corners, 600mm from openings. You also need a discharge pipe to a foul drain.

Combis may give hot water on demand, but so do storage tanks, however combis don't give it very fast, and even when it does it can't cope with more than one tap. Check your water requirements before selecting a boiler type then you can see if what you select can cope with your requirements. Also check your supply pressure and flow rate at peak times or you may be even more dissapointed. For space, can you site the boiler outside? or in the garage?

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links