Finding a leak on a combi

yes both valves shut off, but i cant be certain they are not letting some water in. It would be impossible to say, but they are not old and in good condition.
 
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After 5 days of not using the central heating the boiler is still loosing pressure. I am pretty sure this indicates the leak is on the system somewhere. Is this correct? We have used the hot water only this lat week. Initially the pressure held for longer, but it looses pressure very quickly once you get down to 0.8 bar.
 
After 5 days of not using the central heating the boiler is still loosing pressure. I am pretty sure this indicates the leak is on the system somewhere. Is this correct? We have used the hot water only this lat week. Initially the pressure held for longer, but it looses pressure very quickly once you get down to 0.8 bar.
Could be weeping from the pressure relief valve,a leak on your system,or more unusual,a leak on your heat exchanger.
 
The PRV is not leaking.

If the heat exchanger would i see any water in the boiler ? There is no sign of water in there.
 
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The PRV is not leaking.

If the heat exchanger would i see any water in the boiler ? There is no sign of water in there.

Not normally, it’ll pass down the condensate pipe. Unlikely to be the heat exchanger though imo.
 
Hi all again.

I still have this issue as have just been to busy to get it sorted.

Recently we havent had the heating on and just used hot water. The boiler held its pressure at 1 bar for a good 10 days.

We put the heating on this week and i topped up on monday to 1.4 bar. This morning it was down to 0.2 bar. So it has lost a lot of pressure this week as it has been used most days now it is colder.

I am now 100% certain the issue is not on my new extension loop. This is good news for me.

So the issue is in the main house on the copper system. This was put in by the previous owner and i think it was done in 1990. So 30 years old. 22mm copper feeding runs of 15mm.

In the next 2 weeks i am going to drain down and fit a new magnaclean 2 and also add a leak sealer. I know this is a bad idea but i cant see any other way to find the leak. If this doesnt work then the issue must be on the boiler
 
The usual way to check if the PRV is passing, is to fit a plastic food bag, over the outlet, held in place with an elastic band.

If you are absolutely stuck and have run out of options, drain the system down and find some way to blow air into the system to get the pressure up to 2.5bar. Air will escape much more easily and with more noise, so much easier to trace any leaks.
 
Late night update. Thought i would update my thread before i go to bed as just checked the pressure as i always do before going to bed.

So the pressure is down at 0.3 bar at midnight tonight. So it has lost its pressure fully in 16h's. I have topped up to 1.3 bar again.

Does this give any better clues on what is happening with my system? There are still zero leaks in the house. Nothing is showing up.

I took the pressure in the expansion vessel and its 1.2 bar.

I will tie a bag on the prv tomorrow
 
Hi all again.

I still have this issue as have just been to busy to get it sorted.

Recently we havent had the heating on and just used hot water. The boiler held its pressure at 1 bar for a good 10 days.

We put the heating on this week and i topped up on monday to 1.4 bar. This morning it was down to 0.2 bar. So it has lost a lot of pressure this week as it has been used most days now it is colder.

I am now 100% certain the issue is not on my new extension loop. This is good news for me.

So the issue is in the main house on the copper system. This was put in by the previous owner and i think it was done in 1990. So 30 years old. 22mm copper feeding runs of 15mm.

In the next 2 weeks i am going to drain down and fit a new magnaclean 2 and also add a leak sealer. I know this is a bad idea but i cant see any other way to find the leak. If this doesnt work then the issue must be on the boiler


Your issue is a typical one where the original boiler was an open vented installation where system operation was dependent on system pressure exerted by the header cistern. Fast forward to new boiler that is a sealed system. Worn radiator (valves or compression fittings letting by ) will often weep from the stem. You will not see any wet patches unless the system pressure was dropping like a stone. Often the minuscule leak evaporates making its location a difficult task.

Going by what you have written, it will not be the boiler or the underfloor heating pipe. One suggestion would be to replace the radiator valves in the old part of the house
 
Ok thanks for this info DP

yes we swapped to a combo in 2008.

before they had a dual huge hot water tank which fed the water and the CH. forgot the name of this system.

In the original House I have 4 older rads still. 5 are new.

I am sure it is not on the Ufh or the 2 rads in the extension as these have been isolated.

This all stems from me leaving a cleaner in my system last spring.

I left it for 2 weeks running and then drainEd down And added 2 bottles inhibitor.

after this I noticed the filter collected a fair bit more magnetite. So I’ve disturbed something in the system I think.

I will try what you have said and may in fact replace these rads.
 
Bit of a long shot but if the expansion vessel was recharged during the service you might have a leaking schreader valve, the pressure will keep dropping till the expansion vessel is full.
 
Yes it was charged up on the service and after the service this is when the f22 problem started.

how do I check the valve?

for DP:

I have just checked my older rads and I have actually changed all the valves back in 2008. I have the good dryston trv’s as well plus the lock valves were changed at the time.

so I don’t think these rads are a problem.
 

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