Pressure Dropping constantly

TheTacticsGuy

Moved into my house 6 months ago and noticed the cylinder in the hot press had a tiny leak on the top part. Previous owners collected the water in a bowl and emptied it every few days. We got it replaced and the plumber noticed that the pressure was low, he checked around and didn't notice anything so he pressurized the system and that was that.

Weather is getting colder now so we started to use the heating system. No luck.

Got boiler replaced/upgraded, system balanced and pressurized again. Roll on a few days and I noticed the pressure had dropped again. We contacted the plumber and he explained that we must have a leak somewhere in the system.

Contacted a water leak detection guy and he found a tiny leak on a motorized valve in the utility room. Back comes the plumber, replaces that component and tells me that I'm really lucky if that's the issue. I monitor the pressure for the next day or so and it drops again.

Back comes the water leak detection guy, pressurizes the system with air, goes around with a listening device and can't detect anything. Funnily enough, the system seems to be holding pressure at 2.0 psa.

After this, the system is bled and the water is circulating again. More inspection on every component with no luck. The leak guy leaves and we start to use the heating again. 8-9 hrs later I check the pressure and its sitting at 1.0 psa. This morning it's sitting at ~ 0.85 psa. There's water escaping somewhere and we've no idea what to do next.

One peculiar observation though: One of the tiles in the kitchen gets luke warm when the heating is on, I asked the leak detection guy about this and he said its not a leak, it's an uncovered/insulated joint and that if it was a leak, the water would spread and other tiles would also get warm and you'd notice substances around the warm tiles.

At this point, I've a couple of options:

Sensor valve to detect pressure drop and let more water in Spend thousands ripping up all the downstairs floors to re-plumb the place

First option can only be temporary and I can't afford the second option. What else can I possibly do???

John.G

With the system cold top up the pressure to 1.5 bar then with all rads & hot water cylinder heating on switch on the boiler and watch that pressure gauge constantly for 45 minutes or and see what the pressure rises to, it shouldn't rise higher than ~ 2.3 bar if a grant condensing boiler and not > 2.8 bar if a gas fired boiler otherwise the boiler PRV (safety valve) will lift each time the system is re pressurised.

TheTacticsGuy

I have done this and the pressure does not go past 2.0 psa, in fact, it doesn't even hit it, staying closer to 1.8-1.9 psa

John.G

Well, only other, if unlikely place for a leak (apart form CH system) would be the DHW cylinder coil, not really that easy to check, if you have a zone valve fitted and a balancing valve on the cylinder coil return then shut both which may isolate the coil and again check for pressure loss. If you have a unvented DHW cylinder then its pressure will probably be > than the boiler pressure so the boiler pressure should rise, if vented and coil leak then maybe fill the CWST to just below the overflow mark, dont fire the boiler and see if the level rises.

Damien360

Not a plumber. We have a glow worm condenser gas boiler. Pressure reading couldn’t be trusted.

Plumber put a manual gauge on a pipe in hot press just beside the refill point.

Before the manual gauge, on glow worm, pressure gauge had read low, so it was topped up but it seems that was actually over the relief valve setting in reality and dumped the pressure, hence pressure low reading and failed to light.

Replaced the pressure sensor in glow worm to fix and have had to change it every few years for same thing despite system getting a full flush and has the corrosion prevention solution added.

In short, don’t trust one pressure sensor.

John.G

True but easy enough to see if the PRV has lifted as there will be water somewhere also its the pressure gauge in this case.

TheTacticsGuy

John.G wrote: »

Well, only other, if unlikely place for a leak (apart form CH system) would be the DHW cylinder coil, not really that easy to check, if you have a zone valve fitted and a balancing valve on the cylinder coil return then shut both which may isolate the coil and again check for pressure loss. If you have a unvented DHW cylinder then its pressure will probably be > than the boiler pressure so the boiler pressure should rise, if vented and coil leak then maybe fill the CWST to just below the overflow mark, dont fire the boiler and see if the level rises.

Ok I will try and look into this and report back at some stage, tks