Central Heating Question

My boiler leaks when the gas is turned off,is this dangerous?? help!!

ive just moved into a new house, its previous owners had prepayment meters for both gas and electricity. when the gas credit runs out, the gas turns off and the boiler cant ignite. when it does this there is rust coloured water that leaks from somewhere under the plastic cover on the base of boiler. ive had a look but cant pin point exactly where it comes from. it drips at quite a rapid rate though and easily can fill up a litre tub in half a day. as soon as the gas is topped up and boiler is ignited again it stops leaking completely and works perfectly well even when the heating isnt being used. it just seems to leak when gas connection is off. any help on what is causing this and if its dangerous would be greatly appreciated

6 Answers

Best Answer

this is due to expantion and contraction, when the boiler has gas and is hot the leak seals itself, when its cold the split open and allows water to drip out, its not overly dangerous, its just the drip isnt getting any better and needs attention, hopfully just a nip up somewhere, but possible new boiler

Answered 17th Jan 2012


Member since 28 Dec 2007

Hi Vicky, Its not dangerous, on the gas front! just electrical,if it leaks or blows the trip. either way get someone out. www.gassaferegister.co.uk.

post the job and someone will help


Answered 16th Jan 2012

kelly plumbing Heating & gas

Member since 4 Jan 2012

when the boiler cools after the gas goes off, the metal contracts and allows any loose joints to leak. unless it drips onto electrical components, it is probably not dangerous. it is advisable to get it looked at as it will eventually damage the boiler.
hope this helps.

Answered 16th Jan 2012


Member since 3 Nov 2010

you should get it checked by someone who is qualified to do the job [GAS SAFE] it sounds like a seal/washer has perrished

Answered 16th Jan 2012


Member since 1 Jun 2008

the leak and the gas topup maybe coincidental, the symptoms you have stated point to the diverter valve. this is either faulty or the diaphragm has been punctured. get someone to replace it.

Answered 22nd Dec 2014


Member since 3 Dec 2014

Hi I like to say more but I believe the answer is covered cheers dave

Answered 30th Dec 2015

Quality home improvements

Member since 21 Jan 2013

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