How to find leak in pressurised CH system?is it possible?

terryplumb said:
Is your hot water cylinder pressurised or gravity fed from a cold water tank ( usually in loft ) ? How did you establish that you have a leak on the system pipework/ rads ,as opposed to the boiler ? Does any water come out of the pressure relief pipework ? This question was asked earlier but I don't think you responded.
Click to expand...
Sorry, no I never saw the question. We have a y plan, fully pumped sealed system (words of the installer). Would we have had a header tank and a cold water tank before with a gravity fed system? I'm sure we no longer need the wee header tank but we still have the other cold tank as the installer said he woukdnt need to replace it if it was In Good condition and I think in plastic. I put a bag on the pipe outside from the back of the boiler and no water came out (got this info off this website) but will try a balloon instead as I read someone day that today - woukd this be the pressure relief pipe work you have mentioned?

Sorry, I hope that makes sense.

All we have done so far is:
1) checked all TRV's and valves at top of rads for leaks.
2) checked there was no leaks to any if the new pipework to the rads under the downstairs floor at the hatches.
3). Put a bag over the pipe that runs out the bavk if the boiler (the pipe that is curved back on itself).
4) I also got a pipe run outside incase we need to drain the system in a hurry but this is dry as well.
 
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A few things to note... Some earlier posts gave advice to Increase the COLD system pressure to 2.5 to 2.8 bar. If you do this and then run the boiler the pressure will increase through expansion of the system water to well over 3 bar ,which in turn would cause the PRV to lift .so before running the boiler you would need to drop the pressure back to 1 bar. I personally wouldn't subject a system that MAY have a slight leak to increased ,almost double ,the pressure. Regarding loft tanks , the small f&e tank is redundant now. The larger cold water tank will most likely feed the hot water cylinder ,a picture of cylinder will confirm this, and if so your domestic hot water is still gravity fed. How old is the hot water cylinder ? Its possible that the coil inside has a pin hole leak and CH water is weeping into the dhw .have you noticed any slight discoloured hot water from taps ,or unusual smell from hot water ? Have seen this before on older cylinders which have been on gravity systems ,and then changed to a pressurised one .As the coil is now under much greater water pressure ,its enough to finish it off. And finally are any CH pipes buried in concrete floors ?
 
We had a slight continuous loss in pressure and a few small leaks when we converted to a sealed system - were were warned about the possibility of this by the installer before the work was done. In both cases it was a radiator. (They were originals from when the system was first installed so around 50 years old!). In both cases though, the leak was visible as a very small paint blister on the rad with a faint rust trickle down the radiator. Both leaks were on the front face of each rad and I doubt whether we would have seen them if they were on the back of the rad.

As suggested, check when cold as just like some water leaks that you get on car engines when hot, some leaks seal their self due to expansion of pipes/joints etc. In fact, our old works Ford Focus runabout has a slight water leak on the thermostat housing that only leaks a little when the engine cools down and is left overnight - when hot and running, no leak.
 
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If the system went in last September and you have a 1 year guarantee then there would be no harm in contacting them and seeing if they are willing to have a look for you.

I always caveat old pipework as part of an install and clearly state that I will test the old pipework under pressure but if there are subsequent leaks then that would not be covered under the guarantee and would/could be chargeable.
 
terryplumb said:
A few things to note... Some earlier posts gave advice to Increase the COLD system pressure to 2.5 to 2.8 bar. If you do this and then run the boiler the pressure will increase through expansion of the system water to well over 3 bar ,which in turn would cause the PRV to lift .so before running the boiler you would need to drop the pressure back to 1 bar. I personally wouldn't subject a system that MAY have a slight leak to increased ,almost double ,the pressure. Regarding loft tanks , the small f&e tank is redundant now. The larger cold water tank will most likely feed the hot water cylinder ,a picture of cylinder will confirm this, and if so your domestic hot water is still gravity fed. How old is the hot water cylinder ? Its possible that the coil inside has a pin hole leak and CH water is weeping into the dhw .have you noticed any slight discoloured hot water from taps ,or unusual smell from hot water ? Have seen this before on older cylinders which have been on gravity systems ,and then changed to a pressurised one .As the coil is now under much greater water pressure ,its enough to finish it off. And finally are any CH pipes buried in concrete floors ?
Click to expand...
Ok got some pics of the HWST, hope they ate what you're looking for. I have no idea how old the tank is but the last picture below is of the pipe coming out the front bottom of the tank and the exposed metal in the hole has some rust on it (it's in an Unheated attic though). The pipe from the top goes into the top attic where the cold tank is. There is no odd smell from the hot taps, I woukd smell the inhibitor. No pipes in concrete that I know of but I still don't know how the pipes get upstairs, although I suspect they are the pipes running up the cavity in the kitchen where the old boiler was (4 pipes that run up to where the HWST us). How these pics help.
 

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Madrab said:
If the system went in last September and you have a 1 year guarantee then there would be no harm in contacting them and seeing if they are willing to have a look for you.

I always caveat old pipework as part of an install and clearly state that I will test the old pipework under pressure but if there are subsequent leaks then that would not be covered under the guarantee and would/could be chargeable.
Click to expand...
I intent to speak with the installer as there are a couple of separate minor issues. It would be helpful if I knew what actions i can safely do now ourselves and what I can ask the installer to try if we can't find the leak:
1. Can we put the boiler up to 2.5bar when cold & boiler switched off safely? Will remove the extra pressure after testing.
2. If we put the boiler up to 2.5bar, what are the chances of other leaks/weeps developing? Will the existing weep fully burst?
3. Will we hear the noise from the weep under higher pressure? The stethoscope is a good idea. I have heard a hiss when a screw was put through a microbore pipe, will it be a similar noise at same level?

If we can't find anything from the above, what should we be asking the installer to do (whether we need to pay or not is a side issue) we just need to find the leak.

Or do we leave the weep until it burst fully, then we will know what to fix.

Thanks everyone
Fluff
 
Charge it up cold and go hunting.
It will be under same pressure as when hot. You live there and can spend as much time (at all hours) as you want, without cost associated with calling in the installer. Don’t use leak sealer. If it proves to be on new pipework then seek some form of settlement with installer.
If it’s on old pipework - be pragmatic, as you say... just need to find and eradicate the leak!
 
dilalio said:
Charge it up cold and go hunting.
It will be under same pressure as when hot. You live there and can spend as much time (at all hours) as you want, without cost associated with calling in the installer. Don’t use leak sealer. If it proves to be on new pipework then seek some form of settlement with installer.
If it’s on old pipework - be pragmatic, as you say... just need to find and eradicate the leak!
Click to expand...
Thanks dilalio. I'm an amateur so by charging up, do you mean put the pressure up to 2.5 bar cold then check pipework? Cheers fluff
 
fluff29 said:
Thanks dilalio. I'm an amateur so by charging up, do you mean put the pressure up to 2.5 bar cold then check pipework? Cheers fluff
Click to expand...

Try increments first, if you haven’t done this yet. You may be able to trace leak at lower pressure before going to 2.5 bar.

However, as per @HERTSDRAINAGE2010 I do think you’ll have to resort to lifting floors.
 
dilalio said:
Try increments first, if you haven’t done this yet. You may be able to trace leak at lower pressure before going to 2.5 bar.

However, as per @HERTSDRAINAGE2010 I do think you’ll have to resort to lifting floors.
Click to expand...
Ok, the pressure is normally at 1.5. What increments should we check at? 1.5, 1.7, 2.0, 2.2 I dont think i want risk going near 2.5 as above 2.5 is red on the pressure guage (Worcester Bosch boiler). Thanks again for your patience.
 
On a cold system you have up to say 2.8 bar before the valve starts to lift. So 2.5bar should be fine. You want as much pressure as possible as the higher the pressure the more obvious the leak should be therefore easier to find.
 
It should be about 0.7 when cold; at 1.5 cold, it could well go to 2.2 or higher when hot, and that's not good for it.
 
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