Loss of pressure

[neilpaterson1969]

I have had our Halstead boiler relocated in the house and new radiators and pipework installed.

Everyting has been ok for a few months but recently the boiler has started losing pressure at the rate of about 1bar a week.

I have check all the radiator valves and the blow off valve and the drain cock and they are all dry with no leaks.

Is my next step to start pulling up floor boards to check the pipe connections or is there something else I should be doing first.

Thanks


Neil

 

[John506]

Is the water being discharged due to it being overheated thus causing more expansion which raises the pressure, then the pressure relief valve is discharging the water?

There will be a pipe coming from your boiler to the outside, usually turned back on itself facing the wall, check for any water coming from there when CH is turned on

 

[MANDATE]

Hi Neil!
The pressure should increase about 1 bar when heating is on, say from 1.2 bar to 2.2 bar. But it should never reach 3 bar.
The pressure relief valve is set to blow at 3 bar and the pressure will drop quick if this happens.
If the pressure increase is beyond the 1 bar it is likely due to the expansion vessel losing its air charge (needs re charging) or the diaphragm within the vessel is ruptured (needs new vessel).
If the pressure relief valve opened for whatever reason, I understand they rarely close again properly and leak slightly at the sealing face.
I secured a plastic bag to the discharge pipe and sure enough it collected water.
So first verify the expansion vessel is OK, prove whether the pressure relief valve is the problem.
There is also a Auto Air Valve which allows air to escape but not water and I understand if this is faulty it coud leak water. I understand there is a loose cap on the top of the AAV which could be secured for test purposes.
Another important aspect before you start lifting floorboards.There should be a valve on the 'flow' pipe leaving the boiler and another on the 'return' pipe.
With the boiler off and these 2 valves closed does the pressure still drop.
If it does then you can forget the pipes and radiators cause the pressure is taken from the boiler

 

[Goldspoon]

Hi Neil!

Another important aspect before you start lifting floorboards.There should be a valve on the 'flow' pipe leaving the boiler and another on the 'return' pipe.
With the boiler off and these 2 valves closed does the pressure still drop.
If it does then you can forget the pipes and radiators cause the pressure is taken from the boiler

He would have to wait a few days to discover the answer to this

 

[bengasman]

get an rgi out to check the boiler over and do a service at the same time. ask him when he is on site if he can have a quick check.

 

[neilpaterson1969]

Thanks for all the advice guys.

I filled they system to 1.5 bar last night and left the boiler turned of until this morning and it has lost just over 0.5 bar overnight.

I am going to try the same excercise tonight with the boiler isolated by closing the flow and return valves.

Will let you know ho I get on.

neil

 

[neilpaterson1969]

So I charged the system up to 1.5 bar then isolated the boiler by closing the flow and return valves and sure enough it lost about 0.5 bar overnight again. So I guess it must be a problem with the boiler.

I also tried putting a small back over the discharge pipe outside and no water has collected so I guess it can't be the pressure relief valve.

Anymore ideas?

Neil

 

[MANDATE]

With the heating part of the system and PRV ruled out, I can only think of the AAV.
Under normal conditions the cap I gather is supposed to be loose, but for test purposes it could be made watertight. So might be worth repeating test with cap closed.
Having said that, you would think there would be signs of the leak within the boiler compartment.
A hole in the expansion vessel diaphragm would allow water to pass from the water side to the air side, but if that was the case the air side would be full with water by now and cause a high increase in pressure and the PRV would open.
Sorry can't be more helpful.