Plumbing Question

Pressure in boiler drops to 0 after radiators reloacted

Hi, I have had two radiators moved across the other side of the rooms. I have restarted the boiler etc and filled it upto 2 bar...however this took approx 1 min to drop to 0 bar.

I have now bled all the radiators and the psi still drops but a lot slower. It takes about 5 mins to go to zero.

A couple of people say there must be a leak under the floor where the new pipes have been laid, others say I should try charging the expansion vessel first.

Could someone advise which is the correct thing to do, and also if it this the recharge that is needed can a DIY person do this and whats involved, or should I start knocking holes through the cellar walls to get under the floor?

Any help would be reallu appeciated. Thank you

8 Answers

Best Answer

Assuming you hired a plumber to move the rads, he should have tested his work before he left so you need to give him a call!

Answered 18th Mar 2011

Crafters of London Ltd

Member since 12 Oct 2009

If you have pressurised the system after filling and bleeding the all of the rads and then pressure reduces then you have a leak somewhere. If you have had new pipework then this is the obvious place to start, pressurise the system and look for wet patches in the floor. good hunting.

Answered 18th Mar 2011

ABS Plumbing & Electrical ltd

Member since 14 Jan 2009

I would say you have a leak on your heating system.

If pressure was fine before then it will be on the pipe work that you have altered.

If you want the pressure checking in the expansion vessel then you will need to get an engineer in. Not really some thing a DIYer should be doing.


Answered 18th Mar 2011

Scott Davy Plumbing and Heating

Member since 24 Jan 2010

Hi there,check pipework & fittings [radiator valves first] then check the blowoff pipe [outside].....Brian

Answered 18th Mar 2011

E&M Plumbing & Heating

Member since 26 Feb 2009

sounds more like a leak. charge the boiler back up to 1.5 bar, go outside and see if its blowing out there. if not it will more than likely be a leak involving the move of the radiators. not sure of your situation but normally lift one board, stick your ear to the hole while someone charges boiler upto 1.5 bar,at that pressure you'll hear it if you get house quiet. good luck

Answered 18th Mar 2011

Fendex SW

Member since 29 Jan 2009

Yes in the first intace check for leaks, this is the most likely cause. It doesn;t take much of a leak for the system to loose pressure !

In respect of recharging the expansion vessell, simple process utilising a bicycle or foot pump on the pressure vessell inlet valve.

Should be gas safe registered, even to work on the wet side of the heating system as you have to remove cover from and reinstate boiler.

However good luck



Answered 18th Mar 2011

Southsea Plumbing, Heating, Electrical & Gas Services

Member since 8 Nov 2010

Hi,If you have a leak you will soon know as there will be water leaking through your cellar floor and as it is only taking 5 minutes this will be a serious leak,not just a dribble.Secondly,you have a pressurised system,sounds like a combination boiler system or a sealed system with a pressurised expansion vessel to take up the 10 %volume increase when water is heated.All sealed systems have a 15 mm pipe leading from a temperature and pressure relief valve directly to the outside wall,that will discharge when there is a problem.You will know when there is no air or nitrogen pressure left in the expansion vessel as the water will discharge outside immediately once you pressurised.On the expansion vesel there is a Shraeder valve.,which you can connect a small pressure guage and test the air pressure( usually 1 bar is sufficient ).You can use a normal bicycle pump to repressurise but ALWAYS check the data badge on the expansion vessel as too much air pressure, and the water will not have enough room to expand against the rubber diaghpram and once again water will discharge outside.Job done.Please be aware that as soon as you take the casing off a Combination Boiler to look inside the boiler, that is defined in Gas Regulations as " Gas Work "and you are potentially putting youself at risk as well as your neighbours.My advice,call in the professionals.The expansion valves you can check is the ones remote to the boiler,usually located next to the hot water cylinder in the airing cupboard

Answered 18th Mar 2011

TC Plumbing and Heating/Construction

Member since 31 Dec 2009

If there wasnt a problem before the rads were moved it would suggest that maybe some pipework has been disturbed somewhere and could well be leaking.

It could also be the expansion vessel but that shouldnt have lost all of its pressure from just draining the system down unless the membrane has ruptured but if it has you will eventually fill the system up and the pressure will stay the same and when you heat the water up it will start to come out of the overflow pipe if it doesnt its a leak.

Answered 18th Mar 2011

Bayley Property Services

Member since 21 Nov 2010

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