Dropping Pressure - Can't Find Leak

Turty3

I have an Ideal Icos HE15 boiler that was installed in 2009. About eight months back I noticed the pressure dropped from 1.5 bar to 0 so started monitoring it and topping up manually.

The pressure drops by approx 0.5 bar in a week. We got the installers to check it out & after a couple of checks, new thermostatic valves installed, serviced boiler, they suggested there must be a leak under the ground floor because there were no signs of any leaks on ceilings/floors upstairs.

After several months we got a seek & find mission with camera under the ground floor arranged but there appeared to be no visible leaks. They did find wet rot in an area so we've taken up the floor but found the pipework related to the heating is dry and the wet rot appears to be a separate issue.

I bought a leak sealer to run through the system but the installers told me they already ran a leak sealer through the system when it was installed so I didn't bother running another one through.

Now I'm still at square one with no idea what's causing the pressure to drop, there has never been an error code on the system, I'm topping up manually at least twice per week and I'm starting to pull my hair out about what to do.

Any suggestions, advice, tips would be appreciated.

Pete67

Some possibilities:

1) The relief valve is passing - you can check by examining the outlet which should be piped to an external location, most probably through the wall the boiler is mounted on, or an nearby external wall if it's mounted on in internal wall, it's usually under the flue somewhere. Don't confuse it with the condensate outlet, which should be dripping when the boiler is running. The PRV outlet should be completely dry. If it's wet, or dripping the PRV is leaking and needs to be replaced. That's a job for an RGI, a new valve is about €35 plus the labour.

Also check the operating pressure when the boiler is running, and all radiators are hot. If it's close to 3 bar or even 3.5 bar, then it is likely that the expansion vessel has either lost it's charge, or failed completely. This will cause the pressure to rise when the system heats up due to thermal expansion of the water, which will lift the PRV releasing enough water to drop the pressure to safe limits. When the system cools down again, the pressure will be low due to the loss of this water.

2) Internal leak in the boiler, possibly the heat exchanger. Usually visible as a drip from the boiler casing, but may be evaporated by the heat from the boiler, so may not be visible unless the boiler is shut down for some time. RGI will inspect and advise accordingly.

3) Leak from radiator valves or piping - usually visible, but may not be if the leak is underground or inside a wall.

4) Finally, there may be a leak from the coil in the hot water cylinder, which can be quite hard to detect, as a very small leak will drop the pressure in the system without adding very much water to the cold water storage tank. The only way to check is to isolate the coil from the heating system and carry out a pressure test on it.

Best of luck.

One word of warning, it may be suggested that you add an 'auto-fill' valve to keep the system pressurised. Don't do this, the constant addition of water will lead to corrosion of the steel radiators, associated generation of sludge in the heating system, and ultimately complete failure of the heating system due to blockage of the heat exchanger and radiators. The best option is to find and fix the leak. A good system should only need a slight top up once or twice a year.