Another boiler pressure drop question.

consumers_revenge

Hi,

This is not related to the other thread by someone else.

Had a couple of rads replaced recently and some pipework moved. that was about 6 weeks ago. Only ever used to bleed rads and refill boiler if required before every winter.

Since then I've had to fill up the water into me boiler several times. 2nd time there was a lot of bleeding required to then upstairs rads. Then top up again. This wednesday, 3rd top up and bleed there was only a small amount of air from a single upstairs rad. I keep filling it to 1.5 pounds. All rads get very hot as expected.

The pressure needle on the boiler has dropped again since wednesday by about 1/4 of a pound again and I've refilled, seemed to take quite a lot tonight to get it back to 1.5 pounds. But it probably sounds more when you are refilling it.

I cant find any visible leaks. I havent gone under the upstairs floorboards and theres no wet on any part on the ceiling ( the downstairs rads were moved but cutting/resoldering the pipework upstairs. )

As the system was fully drained and is there likely to be a leak or just air pockets etc until its fully bled?

Incidentally I CAN hear a dripping by the top of the changed pipework but only when the pipes/rad are starting to heat up for 20 secs or so then its silent.

Thoughts please?

missile

If you can hear dripping, it certainly "sounds" like you have a leak rads.
Why were they replaced?
I would contact the tradesman who installed.

nofoollikeold

1. If the dripping sound stops, my guess would be the ticking from pipe / radiator expansion, rather than a leak.
2. Could well still be air in the system, particularly as it was drained down to replace radiators. If you have a hot water cylinder, then the primary coil can hold quite a bit of air, which also needs to be bled. Otherwise the air inside it just gets moved round to the radiators.
3. Bleed with the system off, otherwise the pump moves air round the system. On the basis that air rises, I like to do the lowest radiators moving upwards.

Not that it really matters, the pressure gauge registers in bar pressure, not in pounds.

consumers_revenge

thanks for replies. Its a combi worcester bosch 30cdi.

any idea where else needs to be bled other than the rads please

2 old rads were knackered so were replace, 2 other rads were moved so I could get a sound proofed wall installed.

can hear the dripping literally only when one rad is heating in the area above the pipework. goes and stays quiet apart from that, that why I dont think its a leak?

consumers_revenge

Also just noticed I never opened 1 rad so it was freezing.

southcoastrgi

Are you sure it's dripping you can hear ?
I would say it's the expansion of the pipes that's making that sound, you would have seen evidence if it was leaking

consumers_revenge

That’s what I am thinking.

Hearings been on all evening and can’t/haven’t heard any dripping.

Going to give it another 48 hours before I check pressure in boiler again to see if there’s another drop. Otherwise I’m checking every 10 mins.

consumers_revenge

Had a look earlier and the pressure dropped a bit again.

Did notice the pipe that goes outside is slowly dripping.

Can someone explain what this pipe relates to please? Something about a pressure relief valve not seating right? Or faulty.

Are these expensive to have fixed?

Don't believe the dripping noise from rad was anything bar expansion.

Thanks.

JohnB47

Ah yes. It looks like your pressure release valve has opened at some point. This is a safety valve that opens when the system pressure gets too high - usually around 3 to 3.5 bar.

Then, even though it has re-seated and the initial problem that caused it to open may have been solved, dirt may have got onto the seal and is stopping it re sealing properly, hence the drip and drop in pressure over time.

PRVs aren't that expensive - you can search the internet for yours but a plumbers rates are another thing.

Edit: then again, perhaps there is a problem and this needs to be fixed before replacing the PRV. Perhaps your expansion vessel needs re presurising.

consumers_revenge

would the ev be working correctly if I set it at 1.4 bar and when the CH is on it raises to 2.4 ish then starts coming down again as the system cools.

Im presuming here that once it goes to about the 3 bar mark ( which it might have done after the refit or filling would have cause the prv to unseat and now drip?

thanks.

JohnB47

Sorry for the late reply.

OK, I am not a plumber - just a keen DIYer.

My Worcester Bosch boiler has lost expansion vessel pressure twice in the 18 years I've had it. First about five years ago and again about a year ago.

On both occasions I was able to do the re-pressure myself, with the help of the internet, a pressure gauge and a bicycle pump. On neither occasion did my PRV 'blow', so I was lucky there.

My current pressure ranges from 1.4 bar (cold) to 2 bar (heating full on for a while).

Before the re-pressure it was going from 1.4 to about 2.8

The range you quote does seem to indicate that the expansion vessel needs re-pressurising or maybe even replaced.

Of course there may be other reasons for your problem. As I say, I'm not a plumber.

I would have a plumber back to look at/replace the PRV and check if an expansion vessel re-pressure is needed.