Losing pressure in Central Heating system - going crazy!

cheme7676

Hi all,

I'm losing around 1 bar every ~5 days in my CH system (faster if CH runs more frequently). I ONLY lose pressure when CH is running.

I have done/checked the following:

• Isolated boiler for 3 days and topped up to 2 bar. CH pressure held and bone dry condensate outlet. After deisolating, also no loss of pressure observed.
• Whilst running CH, had a bag tied around PRV and bone dry for a week. Despite this still losing pressure
• Changed all "worn" out looking radiator plugs with new ones and PTFE, did not help
• Did a bit more tightening to all valves, did not help, still losing pressure
• Wrapped tissue around all valves. Vast majority showed no kind of discolouration. Around 3 valves showed a tiny drop of discolouration but wasn't conclusive given I'm losing about 1 bar every few days. Also I did a rad bleed in between so could be this. I have reapplied tissue to the 3 valves and will check in a couple days
• Cannot see any obvious signs of water damage on walls or ceilings, I have white ceilings and walls, I would've expected it to definitely show up somewhere
• Expansion vessel is new, I tested the valve very quickly and air came out. Looks okay

For context:
1. My boiler is an Ideal Logic Combi 35 which was installed in 2012
2. House was built in 2012
3. I've recently had new parts in the boiler: diverter valve motor, expansion vessel, PRV, flow turbine, condensate trap & spark generators
4. I used 3L of sentinnel sealer which slowed it down significantly for 2 weeks but then quickly went back to its normal behaviour

I am absolutely stumped. The only thing I can think about is that the pipework expands and leaks only when hot and possibly evapourating before I can catch it. I can't find anything anywhere and feel like I'm going to go crazy. This water has to be going somewhere?

Any ideas as to what else I can do to find this thing?

tacpot12

You have done well so far. I suspect, as you do, that you have a leak from the pipework. The amount of water that needs to be lost to drop your system pressure from 1.5 bar to 0.5bar is very small; I think this is the reason that you are not seeing physical evidence of the leak. It's probably leaking under a floor or in a wall, and the water is getting absorbed before you can see it. 

I think a thermal camera might work for you if you can rent one or find a plumber with one who will help you find the leak. I'd expect the leak to show up as a warm circle around a pipe. It's more likely that the leak is at a joint, but don't discount any areas where work has been done in the house just before the leak appeared - a nail or screw might have nicked a pipe. Try to think back if there has been any work that might have caused any damage, even moving furniture might have knocked a pipe or radiator to cause a small leak. 

I feel for you, but it is worth persevering to find the leak.  

FreeBear

tacpot12 said: It's more likely that the leak is at a joint, but don't discount any areas where work has been done in the house just before the leak appeared - a nail or screw might have nicked a pipe.

I have seen the acid flux plumbers use eat through copper pipes - If one slapped enough on to sink a battleship and didn't bother cleaning it up, 10-12 years would be enough time for a pin hole to form. If you can get access to the pipework & joints, look for a green fuzzy deposit around any soldered joints. These would potentially be the source of any leak.

cheme7676

tacpot12 said:

You have done well so far. I suspect, as you do, that you have a leak from the pipework. The amount of water that needs to be lost to drop your system pressure from 1.5 bar to 0.5bar is very small; I think this is the reason that you are not seeing physical evidence of the leak. It's probably leaking under a floor or in a wall, and the water is getting absorbed before you can see it. 

I think a thermal camera might work for you if you can rent one or find a plumber with one who will help you find the leak. I'd expect the leak to show up as a warm circle around a pipe. It's more likely that the leak is at a joint, but don't discount any areas where work has been done in the house just before the leak appeared - a nail or screw might have nicked a pipe. Try to think back if there has been any work that might have caused any damage, even moving furniture might have knocked a pipe or radiator to cause a small leak. 

I feel for you, but it is worth persevering to find the leak.  

Thanks for this, very useful. I wouldn't mind purchasing a thermal tracing service however, I was under the impression that they are extremely expensive. I want to bring them in with full confidence that I've exhausted my options and have 100% ruled out the boiler.

For some context on work I've had done on the system itself:
1. January 2023, I was losing pressure quite regularly and going into F1 fault. Plumber came and found expansion vessel flat and replaced the vessel and the PRV. Leak sealer was also added (just in case). Worked perfectly and no pressure loss since.
2. May 2023, hot water wasn’t always coming on when hot taps opened. Diverter valve motor was sticking and replaced.
3. October 2023, L2 fault develops. Plumber first visit supplied and fit new flow turbine and condensate trap. Boiler worked for a week then went back into F2. Plumber changed spark generators and this permanently fixed this issue.
4. November 2023 (exactly 3 weeks later). F1 arises with pressure loss. I topped up to 1.5 bar, then exactly 7 days after goes to 0.5 and drops into F1 again. Rinse and repeat

It might just be a coincidence that the the work done in October 2023 resulted in the pressure being lost, perhaps due to more demand on CH system going into colder months?

Work elsewhere, there is genuinely nothing that I can recall since October and now.

cheme7676

FreeBear said:

tacpot12 said: It's more likely that the leak is at a joint, but don't discount any areas where work has been done in the house just before the leak appeared - a nail or screw might have nicked a pipe.

I have seen the acid flux plumbers use eat through copper pipes - If one slapped enough on to sink a battleship and didn't bother cleaning it up, 10-12 years would be enough time for a pin hole to form. If you can get access to the pipework & joints, look for a green fuzzy deposit around any soldered joints. These would potentially be the source of any leak.

I'm not 100% sure but I believe that the majority of the pipework I have is plastic. The metalwork I have is that attached to the boiler. If I recall correctly last year, when I had some floorboards up, I just saw something like a distribution header which was all plastic. Does it affect this too?

FreeBear

cheme7676 said:

FreeBear said:

tacpot12 said: It's more likely that the leak is at a joint, but don't discount any areas where work has been done in the house just before the leak appeared - a nail or screw might have nicked a pipe.

I have seen the acid flux plumbers use eat through copper pipes - If one slapped enough on to sink a battleship and didn't bother cleaning it up, 10-12 years would be enough time for a pin hole to form. If you can get access to the pipework & joints, look for a green fuzzy deposit around any soldered joints. These would potentially be the source of any leak.

I'm not 100% sure but I believe that the majority of the pipework I have is plastic. The metalwork I have is that attached to the boiler. If I recall correctly last year, when I had some floorboards up, I just saw something like a distribution header which was all plastic. Does it affect this too?

Soldered joints will be for copper only. Plastic pipe will be push fit fittings which the manufacturers claim a 25 or even 50 year life on. A nail or screw would be the primary suspect if the leak is somewhere in the heating system. It might be possible that the leak is inside the boiler as a result of various components being changed. Unfortunately, much of this will be hidden behind a cover that you shouldn't be removing unless Gas Safe registered. So I'm afraid an engineer needs to investigate further.

If you do decide to get someone in with a thermal imaging camera, pick a really cold day and get some images of the whole house. This will highlight where you are losing heat and you can target efforts to insulate & draught proof more effectively.

cheme7676

FreeBear said:

cheme7676 said:

FreeBear said:

tacpot12 said: It's more likely that the leak is at a joint, but don't discount any areas where work has been done in the house just before the leak appeared - a nail or screw might have nicked a pipe.

I have seen the acid flux plumbers use eat through copper pipes - If one slapped enough on to sink a battleship and didn't bother cleaning it up, 10-12 years would be enough time for a pin hole to form. If you can get access to the pipework & joints, look for a green fuzzy deposit around any soldered joints. These would potentially be the source of any leak.

I'm not 100% sure but I believe that the majority of the pipework I have is plastic. The metalwork I have is that attached to the boiler. If I recall correctly last year, when I had some floorboards up, I just saw something like a distribution header which was all plastic. Does it affect this too?

Soldered joints will be for copper only. Plastic pipe will be push fit fittings which the manufacturers claim a 25 or even 50 year life on. A nail or screw would be the primary suspect if the leak is somewhere in the heating system. It might be possible that the leak is inside the boiler as a result of various components being changed. Unfortunately, much of this will be hidden behind a cover that you shouldn't be removing unless Gas Safe registered. So I'm afraid an engineer needs to investigate further.

If you do decide to get someone in with a thermal imaging camera, pick a really cold day and get some images of the whole house. This will highlight where you are losing heat and you can target efforts to insulate & draught proof more effectively.

Inside the boiler, I've had 2 gas safe engineers take a look and ruled out the inside, they couldn't see any signs of water leak.

For the plastic pipework, I was told that if it was an issue with the pushfit fittings, then I'd probably end up seeing a pressure loss very quickly (as opposed to over the course of a few days). Is that true? Also wondering how only losing pressure when CH is on plays into this. Total speculating but if we assume a pipe has had a little hole due to a nail or something, then I would've thought I'd still observe pressure loss even when CH is off?

PS, you can probably tell I'm not plumber by any means.

One idea which I've just been researching is the "cheap perfume trick". A non-convention method granted but is it worth a shot?

ThisIsWeird

Hi Cheme.
Darned annoying, eh?! There was another recent thread with the same head-scratching issue - not sure how that turned out.
You've had a few repairs carried out on you boiler recently, but there's no reason to suspect any connection with this.
When you top up the pressure, how much water do you think is being fed in?! Hard to know, but surely a good few seconds of 'hisss'?! That must surely be at least a cupful of water? I'm guessing that if this is a leak from a pipe, joint or radiator, it'll be bludy noticeable. So I'm equally guessing that you just haven't come across it yet...
Or, it's escaping some other way. The one thing you haven't mentioned is the condensate pipe. This can be awkward to monitor as water comes out in normal use, and you have seemingly no loss when the boiler ain't running.
Hmmmm, I wonder if smellies added to the water could be a great idea?! You'd be focussing on this pipe, so it should be obvious if system water is also coming out there. 
Assuming the smelly wouldn't cause any harm to internal parts - I can't imagine a small amount would - then you'd need to set up the condensate outlet to empty into a loose-lidded container so it's caught and can be sniffed.
Now, are there such smelly additives?!
Is you system pressure pretty stable in use - does it fluctuate much up and down with temp?

ThisIsWeird

Do you have a magnetic filter installed? If so, adding such stuff would be dead simple.
I've just seen a YouTube vid on just this, and found a thread on a forum about an example.
I cannot say it won't cause any harm to, say, rubber components, but I'd consider it unlikely especially if only a teaspoon was added. Your system can always be drained and refilled if concerned.

cheme7676

ThisIsWeird said:

Hi Cheme.
Darned annoying, eh?! There was another recent thread with the same head-scratching issue - not sure how that turned out.
You've had a few repairs carried out on you boiler recently, but there's no reason to suspect any connection with this.
When you top up the pressure, how much water do you think is being fed in?! Hard to know, but surely a good few seconds of 'hisss'?! That must surely be at least a cupful of water? I'm guessing that if this is a leak from a pipe, joint or radiator, it'll be bludy noticeable. So I'm equally guessing that you just haven't come across it yet...
Or, it's escaping some other way. The one thing you haven't mentioned is the condensate pipe. This can be awkward to monitor as water comes out in normal use, and you have seemingly no loss when the boiler ain't running.
Hmmmm, I wonder if smellies added to the water could be a great idea?! You'd be focussing on this pipe, so it should be obvious if system water is also coming out there. 
Assuming the smelly wouldn't cause any harm to internal parts - I can't imagine a small amount would - then you'd need to set up the condensate outlet to empty into a loose-lidded container so it's caught and can be sniffed.
Now, are there such smelly additives?!
Is you system pressure pretty stable in use - does it fluctuate much up and down with temp?

It’s honestly the worst and super stressful. I would be less stressed if my isolation test on the boiler proved the HX was faulty and the whole thing needed replacement!

I don’t know the answer to that, but I know how much water is coming out when I bleed the radiators. So draining around 300ml from a radiator gave me approximately 0.2 bar of pressure loss when I checked it on a cold system a few days ago. So definitely at least a cupful when topping up after an F1 fault.

I agree with the noticeable comment however if the leak only occurs when the system is hot, it tells me that it’s probably evaporating too quickly (considering this is a relatively slow leak) which makes it harder to catch.

Boiler is pretty stable when in operation yeah. I don’t see any fluctuations. I get around a 0.4 bar increase from cold to hot once CH is turned in.

i can add some perfume for sure and monitor. I’m back at the house next week and will check out some videos of others who have done it and try my luck. I can’t get a container under the condensate pipe because it’s so close to the drain in the ground there is hardly clearance. Could I wait for a dry day and put some paper or something on the ground and smell it after a few hours or something like that?

cheme7676

ThisIsWeird said:

Do you have a magnetic filter installed? If so, adding such stuff would be dead simple.
I've just seen a YouTube vid on just this, and found a thread on a forum about an example.
I cannot say it won't cause any harm to, say, rubber components, but I'd consider it unlikely especially if only a teaspoon was added. Your system can always be drained and refilled if concerned.

Unfortunately I don’t. However I plan to get one installed with a new boiler (assuming we can rule that the boiler is at fault)

i can just add it through a radiator. Takes a bit more time but shouldn’t be longer than about 15 minutes really. 

I’ll take a look at the videos and see what they do. Il try replicate it next week and see if I find anything