New heating system - gradual pressure loss

[SteveKelly]

Hi there,
Long time lurker, first time poster here.

I recently had my boiler replaced with a WB Greenstar gas combi (34CDi). Sealed heating system. (old system was gravity fed tank system).

Since installation, the pressure gradually drops till it reaches zero, then I have to go up into loft and re-pressurise it.
The company that installed checked all their work (they only installed boiler/associated stuff... and hooked into the existing rads/heating-pipework) and determined all was ok there).
Because much of the pipework beneath the floorboards is plastic, that ruled out the option of running the 'leak-sealing' chemical through the system.
Leaving only option of having the floorboards up and looking for leaks.
One of their engineers spent a day at my place and we did find one leak in the end. He fixed that. And I thought the problem was solved.
That was a couple of weeks ago, with no probs up until couple of days ago
Now it seems the pressure has started to regularly gradually drop again.
The one towel radiator, I noticed the top bar wasn't hot like the rest of it when heating was on (all other rads fine). And I was hearing a couple of the other rads gurgling away at random points through the day.
Then this morning I noticed the power in the shower was a bit lame, on the setting where it's normally jetting out, so afterwards I was up in the loft (I'm in a bungalow) and sure enough the pressure was back down to zero.
I topped it up to 1 bar.
Tonight I come home and just thought I would check it, and it's down to 0.5 bar again
What a pain in the backside!

So...is there anything else, besides 'another-leak/leaks-that-need-to-found-and-fixed', that could be causing this?

Is it likely/possible that there is something wrong with the boiler, and they've just missed it?
Or is most likely to be the 'leak' thing?

thanks in advance for your help
Steve.

 

[Boilerman2]

I would suggest a Hydralic pressure test on the pipework only (boiler isolated) to see if it is the system leaking or if not test the boiler in isolation, going back to the plastic - I assume that it is "Barrier" pipe that has been used ?

 

[SteveKelly]

I would suggest a Hydralic pressure test on the pipework only (boiler isolated) to see if it is the system leaking or if not test the boiler in isolation, going back to the plastic - I assume that it is "Barrier" pipe that has been used ?

Thanks for the quick reply.
I'll have to have a look around for local engineers that are equipped for this kind of test.

Hmm, barrier pipe you say!... this would be a good time to admit my DIY-literacy levels, which on a scale of 1 to 10, would be a 2...3 if I was exaggerating to impress!!
AKA... I don't know what you mean!

All I know is when they had the boards up it revealed a mixture of copper and white plastic pipework, going off to the rads.

 

[oilboffin]

Yup you have a leak

 

[Onetap]

Hmm, barrier pipe you say!... this would be a good time to admit my DIY-literacy levels, which on a scale of 1 to 10, would be a 2...3 if I was exaggerating to impress!!
AKA... I don't know what you mean! .

Plastic pipe is permeable to oxygen, oxygen is absorbed from the atmosphere by the water in the system and then corrodes the radiators.

Plastic pipe used in central heating systems must have a barrier layer that prevents the passage of oxygen. barrier tube isn't needed for H&C water supply systems, but this tube will create problems if used on central heating.

There will be the maker's details at intervals along the tube, make sure they've used the right tube.

 

[dcawkwell]

Drain the system down.
Isolate the boiler from the pipework.
Attach an air compressor and pump it up to 70psi.
Any faulty connection will burst or you will hear the air leaking.
Sorted.

 

[SteveKelly]

Thanks for the info, guys.

I'm now losing all pressure over the course of a day/night.

There was one potential rad joint that might've been the prob, but i've eliminated that.

Saw some good info on the Leakbusters website, and going to follow their order of checking things.
So first checking the things that might be wrong with the boiler installation

First is test the PRV pipe on outside wall, which I'm now doing(balloon over the end, reset pressure, when pressure down again, check balloon for water).

Next is get the installers back to test the expansion vessel in the boiler.

Then failing that, will probably have to get the Leakbusters in to do the whole 'compressed air / thermal imaging / etc' testing. (I hope it doesn't come down to doing this!)

Here's the thing. Yesterday I topped up the pressure again (fom zero)
Today I just checked and it's back down to zero, BUT this time there was no air in any rads! All full and piping hot. (whereas previously, when pressure lost, i've had to bleed the rads, little bit of air on 2 main culprits - this mainly before I got the first leak fixed)

So because this time there was no air in the rads, does that not indicate that it's not an issue with the pipework?

Also, it says on LB's website:
"If the pressure gauge on your boiler moves up and down when the boiler heats up and cools you most probably have a problem with the expansion vessel in the boiler
Another item to check on your boiler is the pressure gauge, does the pressure gauge rise/increase when the central heating is used ie does the needle on the gauge move from its current point eg 1bar to say 1.2bar ? If so it would be worthwhile getting a boiler engineer to check the boiler expansion vessel. "

is that right? cos mine definitely does this. BUT my installers said that this was normal... so who is wrong in this case, them? or Leakbusters?!

 

[dcawkwell]

Thanks for the info, guys.

I'm now losing all pressure over the course of a day/night.

There was one potential rad joint that might've been the prob, but i've eliminated that.

Saw some good info on the Leakbusters website, and going to follow their order of checking things.
So first checking the things that might be wrong with the boiler installation

First is test the PRV pipe on outside wall, which I'm now doing(balloon over the end, reset pressure, when pressure down again, check balloon for water).

Next is get the installers back to test the expansion vessel in the boiler.

Then failing that, will probably have to get the Leakbusters in to do the whole 'compressed air / thermal imaging / etc' testing. (I hope it doesn't come down to doing this!)

Here's the thing. Yesterday I topped up the pressure again (fom zero)
Today I just checked and it's back down to zero, BUT this time there was no air in any rads! All full and piping hot. (whereas previously, when pressure lost, i've had to bleed the rads, little bit of air on 2 main culprits - this mainly before I got the first leak fixed)

So because this time there was no air in the rads, does that not indicate that it's not an issue with the pipework?

Also, it says on LB's website:
"If the pressure gauge on your boiler moves up and down when the boiler heats up and cools you most probably have a problem with the expansion vessel in the boiler
Another item to check on your boiler is the pressure gauge, does the pressure gauge rise/increase when the central heating is used ie does the needle on the gauge move from its current point eg 1bar to say 1.2bar ? If so it would be worthwhile getting a boiler engineer to check the boiler expansion vessel. "

is that right? cos mine definitely does this. BUT my installers said that this was normal... so who is wrong in this case, them? or Leakbusters?!

You may have a problem with the expansion vessel and it needs repressurising. How many radiators do you have. It may be that you have more water in the system than the expansion vessel in the boiler can handle.

 

[SteveKelly]

I have 7 rads. 3 medium size, 3 small, and 1 towel rad.
So not that many, in my little bungalow!

My boiler is WB Greenstar 34CDi, so the standard EV that comes in the boiler should be able to handle that, eh.

I checked the pressure again 10 mins ago, it had gone down to 0.5 in 5 hours I put the heating on, and now back up to 1.2.
This variation... is that right? (leakbuster say no, my WB-approved installers say yes)

 

[dcawkwell]

I have 7 rads. 3 medium size, 3 small, and 1 towel rad.
So not that many, in my little bungalow!

My boiler is WB Greenstar 34CDi, so the standard EV that comes in the boiler should be able to handle that, eh.

I checked the pressure again 10 mins ago, it had gone down to 0.5 in 5 hours I put the heating on, and now back up to 1.2.
This variation... is that right? (leakbuster say no, my WB-approved installers say yes)

If you start off with a system cold and pressure of 1 bar.
With the heating coming on it might go up to 1.2 or 1.3. But then as the system cools it should return to 1 bar. If it goes up and looses pressure when it cools so it is below 1 bar you have a leak.