Complete loss of CH pressure

[Birdthom]

Evening all

I have a Ferroli Modena 102 which is a few years old. For the last few months we have been having to top up the central heating system constantly. I'll top it up to 1.5 bar and leave the heating running as normal, but then after a little while (could be an hour or a day, sometimes several times a day) the CH system will lose all pressure and the pressure guage drops to zero.

We don't seem to have any leaks anywhere in the house. I haven't seen any water gushing out of the pressure relief pipe outside, but then I haven't fancied sitting out in the cold for a few hours waiting for it to happen!

Incidentally, long after all this started the system was accidentally overfilled to well over 3 bar (!) and left running, but this didn't trigger the pressure relief valve and it stayed at over 3 bar until I bled some water out of the system.

Somthing is obviously very wrong but I have no idea what it is. Can anyone help?

Thanks

Tom.

 

[bengasman]

You either have a leak, or someone is stealing your system contents.
My money is on the former.
Try the old sandwichbag/rubber band trick over the prv outlet, any other fault is unlikely to change the speed of the pressure loss

 

[slapper]

tie a loose plastic bag around prv pipe to see if its leaking/letting by

 

[Birdthom]

thanks - I'll try it now.

*rummages around in desk for rubber band and plastic bag*

 

[Birdthom]

Oh dear. I tried the plastic bag trick. Nothing is coming out of the PRV (the bag has only maybe 10ml in it) but the pressure has dropped to zero and been topped back up again about 3 or 4 times in the last 24 hours.

I guess this means there is a pretty big leak somewhere in our system. It's been going on for months but I can't find any sign of it. I am guessing it must be downstairs because if it was upstairs there would be obvious water damage to ceilings etc. Fair assumption? If so, I guess it's a matter of looking under the floors until we find the leak. BUT half the house is suspended floors which have only just been newly carpeted and the other half is laminate over solid concrete floors. It's quite a big house so there are a lot of floors to look under.

Where to start is the next question. We had a radiator in the front room moved (from side to front wall) when we moved in to the house about 13 months ago and that's probably the only work which has been done on the downstairs plumbing in the last five years, so I guess that has to be prime suspect, but I looked under the boards in that room before the carpets were fitted and there was no sign of a leak. After that I have no idea where it could be and the only way to find out seems to be by lifting up all the new carpets. If it's not that then it must be within one of the solid floors and that could be a real nightmare.

Anybody got any ideas? Are there any tests we could do without lifting the floors to find out where the leak is? Help!

Thanks!

 

[bengasman]

next best guess is a compression joint that has come loose.
if you remember or suspect any of these, inspect them

 

[Birdthom]

I'm not sure as I didn't do any of the installation, but I suspect plastic piping was used to move the rad in the front room, which I guess would need a compression joint where it meets the old copper pipework. As you can tell I'm no pro, but does that sound about right?

 

[bengasman]

depends, if you deburr and clean copper pipe, a pushfit will slip on just fine.