Pressure loss on boiler when not running

[laguna]

Hi - I'm looking for some advice on a constant boiler pressure drop. Its a pressurised system in the garage with a Main 28kw boiler 2 years old. Ive had the problem about three weeks or so now. Ive checked the pressure for 4 days at the same time when the system is cold and the pressure dropped about 1bar over this time. Yesterday afternoon 16.00 I turned off the boiler on the programmer (water and heating), refilled the system to 1.5bar and took a photo of the guage every 2 hours until 9.30am. Its dropped about 0.3 bar in 17.5 hours. this is without the boiler running at all, correct me if I'm wrong but the water must have escaped somewhere in the house through the sealed loop of central heating pipework... right? I don't now what sort of volume of water this would be, but there are no visible signs in the ceiling, rads or damp patches anywhere. I'm guessing there problem is underground under tiles and the concrete floor. I'd like to do some more analysis, maybe isolate upstairs and downstairs heating somehow and see what that does...

 

[dancinplumba]

hi, top up boiler then isolate boiler and then see if pressure drops. if not its leak on system, if it drops its on boiler.

 

[chris watkins]

Hi & welcome to the forum, a couple of things, if you are in a standard height, say,2 story house then 1.5 bar is a bit too high more like 1 bar, remember the more pressure you put on a leak the faster the leak becomes. Secondly have a good check around the connections to radiators & the rad valves look for wet but also any staining, it only takes a small amount of water leak to drop the system pressure.
As you say the next option is to try to isolate sections of pipework to break the system down & narrow it down. Cut in a pair of isolation valves one on the flow & one on the return, turn them off overnight & see if pressure still drops.

 

[laguna]

Hi thanks for your comment. I can isolate the flow and return under the boiler thats no problem. Although I don't understand how that would tell me anything new, I say that because last night (4pm) I set the pressure to 1.5 and the boiler wasn't running again (turned off the programmer) until this morning (9.30am) the pressure had dropped without the boiler coming on at all.

 

[dancinplumba]

if you isolate boiler, then you eliminating either the boiler or the system, which has the leak ?

 

[laguna]

Hi there, thanks for the welcome. This problem is really getting to me. Least it sounds like I'm thinking in the right way. I have done a lot of checking in the house around the rads and pipes, luckily (or not) I don't have any carpet upstairs yet so I've even been snooping under the floorboards along long runs of the pipe work and can't see anything and the celings downstairs all look fine too. I've just had all downstairs tiled so I'm dreading theres a leak under all that lot, although I know more or less where all the pipe work is. I will drop the pressure back a little, its a 2 story house with 5 bedrooms. A few people have mentioned trying a leak sealer, as it can't do any harm (apparently), although I've never been a fan of anything that sounds hit and miss. I think get someone to cut me in some valves so I can section areas off, as you say at least this is a pragmatic way to see whats going on. Cheers again

 

[laguna]

Ok thanks, i'll try it.

 

[dancinplumba]

once you have eliminated boiled then start cutting in isolation valves

 

[laguna]

Ok will do. Cheers

I know this adds another variable into the equation, but is there a way the water in the central heating sealed loop which is obvioulsly is fed into the bolier on the flow and return, can this leak into the hot water (cylinder) pipework somehow? Or is there no way in the boiler the two systems could cross over?

I'm just thinking of where the water might be going, thats all.

 

[dancinplumba]

yes its possible you have a split coil inside dhw cylinder

 

[Citiheat]

Have you checked that the pressure is not leaking out of the pressure relief discharge pipe? There is a 15mm pipe from the bottom of the boiler that either goes to a tundish (a funnel shaped fitting that lets you see the water passing through it) or to the outside (More likely). If a tundish, you will see the water dripping into it. If to the outside, it may be obvious that there is water dripping from it or a wet patch on the floor. If it is dripping when the boiler is off, then it will be a faulty pressure relief valve.

 

[laguna]

I went to isolate the boiler last night and found that I couldn't shut down the plastic flow lever. I unscrewed the lever and the screw was rusty, wet inside the hollow cap inside of the lever and moist around the valve. Anyway I carried on with a spanner and closed off both valves. Noted the pressure and left the boiler for 4 hours, no pressure drop. I had to run the boiler then as the house was freezing. I am hoping this is my problem although its only weeping and not gushing, however, I guess as the temp is 75/80 deg's some water could evapourate and also air could be coming out. I'm going to get the valve replaced, hopefully on Friday and carry on checking the pressure thereafter.