pressure

[eldiablo]

Hi
Few weeks ago i posted a question regarding my Baxi combi series 80E and your replies were really helpful here is the post ://www.diynot.com/forums/plumbing/baxi-combi-80e.308208/#2261191

This cured my issues but recently i've noticed the pressure dropping off so the other day I bled the system again and brought the pressure up to 0.70bar and ran it for a minute or so, so that I was sure there was no air in the boiler and then turned off the boiler, I then shut the valves on the flow and return pipes therefore in theory isolating the boiler from the heating system. I left the system turned off for 24 hours then checked the pressure and it had virtually dropped off. I trust what I did confirmed that the leak is in the boiler somewhere but i'm not sure if this has completely isolated the boiler and are these valves completely water tight , I hope you can give me some pointers and advice as to where you think the pressure loss may be.

Many Thanks
Chris

 

[Hugh Jaleak]

First port of call would be to check the PRV discharge outside. Tie a plastic bag over the end, or in the current climate look for the icicle hanging off it.....

 

[eldiablo]

Hi
Thanks for your input, i've checked it but to be on the safe side I disconnected it from the pipe going outside at the boiler and put a large sheet of blue roll directly underneath the boiler to spot any drips from inside anywhere also a container under the pressure relief valve and it is all bone dry even after the pressure has gone to nothing.


Thanks Chris

 

[andytw]

Hi,

The way I see it is this...
If your expansion vessel is pre-charged to 1 Bar then only when the pressure in your system gets to 1 Bar will the bladder in the vessel start to move and allow the vessel to fill with water. Pressurising your system to 0.7 Bar will mean that very little water needs to leak for the pressure to dissapear.

I would pressurize the system to 2 Bar before closing the isolation valves.
For the system to get to 2 Bar would mean that the expansion vessel is half full of water which would now require something of the order of 2 litres to be lost before the gauge registers 1 Bar. 2 litres ought to be locatable.

If the same problem occurs with no leakage from the boiler then I think you have to assume that the isolating valves are not 100 %

andytw

 

[eldiablo]

Hi
In retrospect i may not have completely shut off the valves during my first test (doh!), I did what you said and pressurised the system to 2bar then shut off the valves and left the system for 48hrs when I checked it again the pressure was still the same but as soon as i opened the valves on the flow and return the pressure dropped significantly, so i guess this proves the leak is in the pipework somewhere.
Anyway to get to the point I think ive found the problem, im replacing the back kitchen units at the moment and behind one of them them are two pipes coming out of the floor where once a radiator was and after removing the floor around them there is a compression style elbow joint dripping lots of water and loose aldso it looks like it has been leaking for some time so I have tightened it up and it seems to be watertight now, so i have bled and pressurised the system again and will see if it loses pressure now over the next 24hrs. I will of course replace this union if it keeps its pressure, but many thanks for your help and suggestions, you have been a life saver.

Kind Regards Chris