Underfloor heating leak

[JT101]

Hi all

I have a polypipe overlay underfloor heating system. Unfortunately due to poor project management, the system has been tiled over before I could test it. And now of course I have a leak.

No screws have been used, only adhesive. I'm connecting directly to the barrier pipe, and pressurising to 18bar using a Rothenberger pressure test pump. The pressure drops about 1bar in 30mins. I only got to 2hrs i.e. 16bar last night.

I've left it overnight, and will report back tomorrow but any suggestions of how I can find this leak are welcome.

Could it be an air leak from air still in the system?

[harryagain]

18 bar!!! I'm not surprised it's leaking. Thats over ten times working pressure.

[A.Lee]

18 bar? What are you trying to do - make the pipes split? They will never get to 10 bar in normal service, maybe 4 if you have high pressure, but unlikely. I think the maximum rating for that pipe is around 12 bar, so I'd be checking the documentation to see what it can hold. Surely you know that anyway if you have a pressure testing kit, which is a pretty specialised piece of equipment.

Could be a leak forced by the high pressure used to test it.

[Onetap]

It won't be air, that will just compress. There is a different testing procedure for plastic pipes, because the plastic will stretch slightly under pressure, showing a pressure drop and an apparent leak.

Look on the manufacturer's website or, if they don't specify it, another manufacturer of similar tube.

18 bar sounds excessive, 10bar is usual ISTR.

[Onetap]

The only certain means of finding an underfloor leak SFAIK is helium leak testing, there are leak finding companies. Expensive, but I've no 1st hand knowledge. It may be cheaper to dig the floor up; you may be doing that anyway, if there are several leaks..

With existing floors, with the heating operating, you can sometimes find it by mopping the floor. The floor dries over the pipes first showing the layout and, hopefully, a circle over the leak.

[Piers]

As others have said 18 bar sounds way high. When I installed my UFH system I think it specified the pressure test at 6 bar. I found that the pressure would vary quite a lot based on ambient temperature, but I convinced myself it was fine based on it going back to the same pressure when at the temperature I initially pressurised it at.

I also initially found a bunch of "leaks" where I simply needed to tighten some compression fittings on the manifold. (Do remember you need to isolate the UFH circuit from the main central heating system before pressure testing!)