Drop in Pressure on condensing boiler

emilymch1

For over 3 years i have been battling with drop in preseure on my boiler. All plumbers say it can only indicate a loss of water which means a leak, or a number of leaks. 2 years ago we did indeed find a fairly obviously leak on an incoming pipe, joint was fixed and there appeared to be no problems. This year pressure dropped consistently again, i noticed the drop was very dramatic in the very cold temperatures, once temperatures were minus. I have had a guy with thermal imaging camera - from there using his information we dug floors - and continued digging and a few small leaks which were fixed. A good quality sealer was put into the system - for the first week we thought we were sorted, then temp. began slipping - maybe by about .2 or .3 a day, then again dropped dramatically to 0 in the v. cold weather. I have been guaging it very carefully again for the past 10 days, .2 or .3 of a drop daily - one or 2 days there was no drop. yesterday, - freezing as we all know - dropped to 0 in one day. this morning i brought pressure up and already there has been a drop of over half bar in about 5 hours. i feel we could continue digging and keep find small leaks - and we still wont have the problem sorted. is there anyone out there who might have had similar experiences that can help pleeeeeeeze!!!! i am demented - dont want to dig up all the rest of the floors in vain thanks a mill

Dtp79

emilymch1 wrote: »

For over 3 years i have been battling with drop in preseure on my boiler. All plumbers say it can only indicate a loss of water which means a leak, or a number of leaks. 2 years ago we did indeed find a fairly obviously leak on an incoming pipe, joint was fixed and there appeared to be no problems. This year pressure dropped consistently again, i noticed the drop was very dramatic in the very cold temperatures, once temperatures were minus. I have had a guy with thermal imaging camera - from there using his information we dug floors - and continued digging and a few small leaks which were fixed. A good quality sealer was put into the system - for the first week we thought we were sorted, then temp. began slipping - maybe by about .2 or .3 a day, then again dropped dramatically to 0 in the v. cold weather. I have been guaging it very carefully again for the past 10 days, .2 or .3 of a drop daily - one or 2 days there was no drop. yesterday, - freezing as we all know - dropped to 0 in one day. this morning i brought pressure up and already there has been a drop of over half bar in about 5 hours. i feel we could continue digging and keep find small leaks - and we still wont have the problem sorted. is there anyone out there who might have had similar experiences that can help pleeeeeeeze!!!! i am demented - dont want to dig up all the rest of the floors in vain thanks a mill

How old is your system?

crock!

It must be a great thermal image camera to pick up small leaks

sullzz

Have you had your cylinder coil ruled out as being the problem

DeSmasher

if the boiler is outside away from the house chances are the leak could undergound outside, i dont think its the cyclinder coil as it would'nt drop to 0, it would hold at tank pressure. One other theory is that depending on what way your heating system is piped and filled its possible that the non-return on your filler valve is faulty, and if and this is a big if, with a large pressure drop in your mains with the cold weather, the heating system is losing pressure back through this filler valve. this would not be the ideal way for a system to be piped but it is done.

shane0007

What is the system pipework made from, copper, gun barrel, plastic or a bit of everything?
System should be drained, circuit isolated as much as possible & pressure tested with air.

If there is genuinely that number of leaks, it is time to re-pipe the system as what is to stop further leaks appearing after corrective works. I would also investigate as to why there are so many leaks, what is causing the destruction of your system?

emilymch1

Thanks a mill - to answer the questions i can - system is new - just 3 years old - yes it was a very sophisticated imaging camera was used, but it only traced one leak. i am reluctant to keep digging because the drop in pressure is very erratic in the really cold weather. the drop is very small until we get 0 temperatures, one it gets that cold pressure drops to 0. the system is pressurized, and the piping is about 20 years old. I changed some of the piping when i was renovating about 3 years ago.

the system has been drained before the leak sealer was put in and is due to be drained again. We know the leak isn't outside because of the piping from boiler to house - the piping used had no joints and was completely insulated, all that work was done 3 years ago when we moved the boiler outside.

shane0007

Again the various circuits should be isolated & pressure tested, especially if there is an external below ground pipe run. These are often under or incorrectly insulated. Each run should be tested individually.

emilymch1

thanks. that deffo is the next step before we do anything else. i actually saw the piping used from boiler into house and it was deffo well insulated, it was preinsulated piping, new on the market at the time. should it be possible to isolate house to boiler? thanks for the help. just wondering if you've any comment on the fact that the pressure drops far more quickly in the really cold weather?

emilymch1

Hi i am back again - has anyone any idea as to why the pressure should keep dropping to 0 in a matter of hours once the weather is really cold. I have been monitoring very carefully - while i can understand a .2 of a drop daily indicates that theres a leak, i cannot understand why it would revert to dropping to 0 in matter of hours - the only consistent factor during this drop appears to be v cold temperatures. would turning radiators have any implications? thats the only other factor i can think of.

thanks a mill - i really would appreciate any suggestions

shane0007

emilymch1 wrote: »

Hi i am back again - has anyone any idea as to why the pressure should keep dropping to 0 in a matter of hours once the weather is really cold. I have been monitoring very carefully - while i can understand a .2 of a drop daily indicates that theres a leak, i cannot understand why it would revert to dropping to 0 in matter of hours - the only consistent factor during this drop appears to be v cold temperatures. would turning radiators have any implications? thats the only other factor i can think of.

thanks a mill - i really would appreciate any suggestions

Has anybody checked the expansion vessel pressure & the safety valve discharge pipe?

emilymch1

yes, all have been checked and monitored,

shane0007

Then each pipe circuit should be isolated & pressure tested individually or re-pipe the lot.

emilymch1

thanks shane, i'm resigned - i would rather do anything else!!! have to face the music i'm afraid

emilymch1

Shane - does this make any sense to you??? I am quoting "The ghird possibility which is ofen overlooked is low pressure ont he dry side ofhte pressurisation unit diaphragm. The pressure in a sealed system is mainained by means of a chamber either integral within the boiler or an external cylinder, depending on the size/design of the heating system. In either case these units are divided into a "wet side" radiatiors etc., and a "dry side". The division is provided by a flexible neoprene diaphragm. Pressure of the wet side/heating system is maintained by the "dry side" of the diaphragm being changed to, most commonly, around 1 bar with air (no special gas is used). It is quite common that the dry side pressure over time. What happens then is that the consumer/heating engineer tops up the pressure on the wet side but when the heating starts the expansion of the water in the heating system as it gets warm blows off the excess pressure through the high pressure relief because there is nowhere for this expansion to take place (the pressure uit "dry sie" is deflated so theres nowhere for the water pressure build up to go). When the system cools down the heated water in the system contracts (remember that in this situation a quantity of water h as been expelled through the pressure relief valve as it heated up) and the control system detects this loss of pressure and thus oes ot start on the next heating cycle.

shane0007

shane0007 wrote: »

Has anybody checked the expansion vessel pressure & the safety valve discharge pipe?

Yes, hence I asked the above question.
To check the expansion vessel pressure, the system pressure must be deflated to take the pressure away from the diaphragm otherwise you will just read system pressure if the the airside is deflated.

Wearb

That is exactly why the question was asked in #11. You answered that this was checked out and OK. Perhaps you should reconsider your answer to that question, to be sure you can be certain there is adequate pressure in the dry side of your expansion vessel and that the diaphragm hasn't ruptured and caused the problem that you referred to above. Perhaps your answer was correct, but the statement above refers to this possibility.

emilymch1

ok, its all a bit technical for me - as far as i know all have been thoroughly monitored but i will double check today. thanks a mill

emilymch1

i can confirm that all the above has been checked. nothing for it now but to go isolating and pressuring as you suggested.

thanks