Boiler Pressure Loss :-(

alanobrien

Newish pressurised boiler loosing pressure.
System converted from gravity fed to fully pumped
about 6 months ago.

No visible signs of leaks from any joints or ceiling etc.
Original hot water tank i guess maybe 30 yrs old ?
2 zone valves 1 heating 1 hot water.
Ground floor pipe work into concrete floor.

Any easy way of diagnosing where the leak is ?

Is a zone valve pressure tight ?
If so i could close off the hot water for a day or 2 to see if the press loss stops in which case i guess the loss is through the heating coil.

If not then i guess its under the concrete floor

Any pointers much appreciated.

moneysavingplumber

alanobrien wrote:

If so i could close off the hot water for a day or 2 to see if the press loss stops in which case i guess the loss is through the heating coil.

If not then i guess its under the concrete floor

Any pointers much appreciated.

If it was the cylinder coil then it would raise the level in your cold water storage tank, especially if you repressurise when it's full. This is a common problem with pressurising old systems. Try Fernox injectable leak sealer, if it's only a small weep from a joint this might fix it, if not then the pipe work will need investigating, especially if it's unprotected in the screed.

Have you checked that the pressure relief valve isn't letting by? Also you will need to check the pressure of the expansion vessel, when cold.

em512

Has the weather turned alot colder in you area in the last couple of days?
I got new pressure boiler and it works fine through the summer months but as soon as we get alittle frost the pressure drops in my water supply. You can get your local water board to run checks to see what the pressure coming in is and if its low they can sometimes boost it alittle. Normally my system settles down after a few days. You can also buy special stuff to put though your sytem that can fix minor leaks. You have to drain system then put in this liquid that fixes the leak if one is present.

All of what i just said probs wont help but i thought id mention it.
Hope you get your problem fixed.

alanobrien

moneysavingplumber wrote:

If it was the cylinder coil then it would raise the level in your cold water storage tank, especially if you repressurise when it's full. This is a common problem with pressurising old systems. Try Fernox injectable leak sealer, if it's only a small weep from a joint this might fix it, if not then the pipe work will need investigating, especially if it's unprotected in the screed.

Have you checked that the pressure relief valve isn't letting by? Also you will need to check the pressure of the expansion vessel, when cold.

Checked the pressure relief valve, thats ok.
Pressure drop was gradual at first, now its about 5 mins to complete loss. If it is leaking into the tank then i guess i should see leakage through the hot water expansion pipe back into the cold tank ? will give that a look when i am back home.

Not sure if i can isolate the tank itself i recall seeing some valves, so that may also be an option.

I hope the expansion vessel is ok the boiler is only 2 mins old. Checking pipework in the floor isnt an option as its cemented in. If the problem is there then its a re-pipe job from upstairs i guess.

Wherever it is, its significant leakage and has increased gradually which gives me some hope its the cylinder.
At least that's relatively easy to replace.

thanks for the response.

alanobrien

em512 wrote:

Has the weather turned alot colder in you area in the last couple of days?
I got new pressure boiler and it works fine through the summer months but as soon as we get alittle frost the pressure drops in my water supply. You can get your local water board to run checks to see what the pressure coming in is and if its low they can sometimes boost it alittle. Normally my system settles down after a few days. You can also buy special stuff to put though your sytem that can fix minor leaks. You have to drain system then put in this liquid that fixes the leak if one is present.

All of what i just said probs wont help but i thought id mention it.
Hope you get your problem fixed.

Thanks for the response. I have seen this leak sealer stuff but am reluctant to use it (its an old engineer thing) i would rather try and find the problem first and then figure out a solution.

that said given the speed of the pressure drop i doubt it would get to the leak quick enough to seal it off

Forgot to mention, i started to hear bubbling noises from the hot water cylinder recently that sound very like a kettle boiling, this is odd given the thing shuts off at 60c so that also gives me some hope the cylinder coil is leaking.

moneysavingplumber

Well 5 minutes for complete pressure loss is major. If it's the coil it will fill the cold water storage tank via the cylinder cold feed, although you may get a spurt up the vent pipe. If it is the coil then you are going to have a contaminated domestic system now. Wait until your cold water storage tank is full and nothing is drawing from it, then pressurise the heating a few times, if it's the coil then you should see a significant rise in the level in the CWST. If that's the case I would change that as well as the cylinder as it will have ingressed a fair amount of CH water that will be hard to eliminate. If it's not that then check the PRV isn't dumping the pressure when you pressurise it, which would suggest the exp' vessel charge pressure.

Failing that you might have to look at replacing your downstairs pipe work with drops from above, as I would suspect that would be the source of a major leak like that.

Leak sealer won't touch a leak that big.

plumb1_2

After you have checked its not comeing through the coil,into the tank.
.Also you should see some discolouration to the water coming through your hot water taps if it was the coil.
Valve off the downstairs supply and re-pressurise.

alanobrien

plumb1 wrote:

After you have checked its not comeing through the coil,into the tank.
.Also you should see some discolouration to the water coming through your hot water taps if it was the coil.
Valve off the downstairs supply and re-pressurise.

indeedy, thanks for that i thought it was an option.
i think the water looks odd but then i have no sense of colour so first i will try and oisolate the tank re pressurise and see what happens if that is ok then i will cap offf the lower circuit and re pressurise to see what happens.

either way it lools like work

moneysavingplumber

If it's been flushed correctly when converted you aren't likely to get much discolouration, you should get the scent of Fernox! Although having lost pressure so many times it's likely to be thoroughly diluted now.

alanobrien

moneysavingplumber wrote:

If it's been flushed correctly when converted you aren't likely to get much discolouration, you should get the scent of Fernox! Although having lost pressure so many times it's likely to be thoroughly diluted now.

I flushed every rad individually and replaced alll the valves before the boiler was fitted and the corgi engineer also fluhed the whole system several times so it was running very clear only a few months ago. Given the losses to date i dont expect to see much colour in the water or smell anything like inhibitor.

Anyway, i am back home now so i will do some more investigation over the next day or so and try to figure out what the problem is before i get the engineer back to fix it.

alanobrien

Just to close this one off..........my problem is the hot water tank coil.

I found it by locking off the boiler via the isolation valves, opened the system and hot water tank zone valves then pressurised the system with mains.

Low and behold the level in the cw header tank in the loft began to rise at an alarming rate.

At least replacing that is less painfull than digging up the concrete floor or ripping up floorboards to re pipe !

Thanks to all of you who provided pointers.

Just got to get the tank replaced now