Finding a leak in the central heating

vallo

The gas-fired central heating system is mains-fed and the pressure drops below one bar over a few days. When the boiler won't fire, I have to top up the system using the non-return valve.
I suspect a leak somewhere under the ground floor.
Any ideas on how to find this without lifting all the boards?

crosstownk

I assume by 'mains fed' you mean a sealed system that requires you to open a valve to fill it, from the mains.

Check your ground floor ceilings for dampness - just in case it's an upstairs radiator. Check all the connections at each radiator for leaks/weeps. Check the expansion vessel - I've seen these leak too. If you've any motorised valves, then check them too. Also, check the automatic air vent at the top of the hot water cylinder coil.

If you find nothing then it could require the boards to be lifted downstairs.

vallo

I've ticked off all those options ... I was just wondering if plumbers had any other leak-finding tricks!

Thanks anyway ... looks like it's a floorboard lift for me!

Vmaxer

Vallo, Whats the pressure like when the boiler is at full temp? I had a similar problem and I think I have it solved.

My Gas boiler was loosing pressure every couple of Days and I would top it up to one bar by letting in water by the non return valve. Problem was that when the heating is on I have pressure of 3bar and slightly above even, one Morning last week a pipe burst at the joint and destoyed a ceiling on Me. So I replaced the joint and everything OK but the pressure was still high when hot and gone to zero again after a few days.
So last Night I discovered that the water I was adding to the system was being vented once the pressure went above 3bar so what I had to do was recharge the expansion tank with air through the valve, this would allow for the water to expand when hot and now the pressure stays at 1 bar when cold and doesn't get above 1.5 bar when hot. If You have high pressure in the system when hot then id say the water is being vented and not leaked.

Hope this helps
I'm no plumber but it solved My problem which sounds similar to Yours..

vallo

Thanks for that ... it sounds promising! I'll check this out over the next few days. If it saves me pulling up floorboards it'd be great - I'll owe you a virtual pint.

JamesM

Dubsmax wrote:

So last Night I discovered that the water I was adding to the system was being vented once the pressure went above 3bar so what I had to do was recharge the expansion tank with air through the valve, this would allow for the water to expand when hot and now the pressure stays at 1 bar when cold and doesn't get above 1.5 bar when hot. If You have high pressure in the system when hot then id say the water is being vented and not leaked.

Certainly if the pressure vessel is not doing its job, there will be nowhere for the expanded water to go, and the safety valve can blow if the pressure gets high enough. If the pressure gets high enough some water can escape at the rad valves and might not be noticed. If the system is 15 or 20 years old, the diaphragm in the pressure vessel can burst, leaving no room for expansion, and the vessel will have to be replaced.
Jim.

flocker

Also check, before you start lifting floors, the safety valve and the outlet pipe that should go to outside or to a drain. The valve could be weeping allowing the system pressure to drop. If it's wet or dripping the safety valve may need to be replaced. Otherwise check all visible heating joints (rads, pipework in hot press and at the boiler.)
If the pressure vessel is gone the pressure will continue to rise when the heating is on till it blows off at the safety valve. Re-charging the pressure vessel doesn't always work, the diaphram may be leaking. Filling the system via a filling loop you should only need 1 - 1½bar when cold.
Sometimes if your floors are concrete you can see a darker grey colour where there is a leak.

BSHAC

I know it's too late for this thread but for anybody else who like me uses boards.ie to find solutions to diy problems I thought I would post this. I had a similar problem and was on the verge of taking up all the floor boards when I heard of leak busters based in Bray (01) 2760899, a leak detection company. THey operated on a no-leak-no-fee basis and found the leak using listening devices and now my heating is working perfectly and only one isolated hole in floor to repair. Several plumbers had told me that finding leaks is not possible but now I know it is. The cost was covered by my house insurance.

311

What was the cost and how long where they there?

BSHAC

350 and 3 and a bit hours