Testing CH install for leaks?

[EricP]

I want to pressure test my installation as I complete it and thought compressed air was a good test for leaks.

Combi's seem to dump pressure at about 3bar, so, if I assume a bar is

16 psi, then if I pressure to 50psi and leave for a period, would this be a fair test?

Or have I got the figures wrong? I don't want to hear bangs as all my new rads bulge out. :))

Cheers

[Andrew Gabriel]

That's a bit high. I normally used 2 bar, ~30 psi, or 3 bar, 45 psi max. Air leaks much faster than water would, but because it's compressible, it can take a long time for a small leak to show up as a pressure drop. What I suggest you do is buy a can of gas leak detector spray (something like LD-90, from a builder's merchant or plumber's supplier), and spray it on all the joins and fittings when the system is pressurised. It can take a minute to soak into the join, and then it will grow a frothy 'cuckoo-spit' lump if you have a leak. It works much better than soap or wasking-up liquid. In the case of compression fittings, you can try tightening them up a bit to see if that stems the leak.

One thing to be aware of -- a heating system pumped up to 2 bar has a hell of a lot of energy stored in it, and if something completely fails like a joint separating, it will do so with a big bang. I did my testing in small sections, like a couple of radiators and associated pipework at a time, using pushfit endcaps to seal the sections. If you want to see how far a radiator pumped up to 2bar will fire a pushfit endcap when you release it, make sure you are wearing eye protection, ear defenders, and there's absolutely nothing breakable (like windows) in the house. Also, it takes a lot of energy to pump up a couple of large radiators up to 2 bar by hand -- you'll only manage it if you're fit.

I think my radiators claimed to have been tested to 10 bar, but their max working pressure was much lower -- I forgot what it was.

[EricP]

I am decrepit, but I will survive! :))

Thank you sir. Nice info.

:))

[IMM]

If the leaking pressure is too high it will not form bubbles.

[EricP]

You mean it will just dribble?

That's ok, I can do dribble. :)

[tarquinlinbin]

dont bother,just fill it up and check it..!!

[Ed Sirett]

In which case you'll hear it hissing - even if you can only get 0.25 bar in.

[Aidan]

No.You do not pressure test with air. You are proposing subjecting an untested system to 2 or 3 bar of air pressure? A pressure test should disclose any leaks and also any weak joints or components which will fail under pressure. If it fails rather than leaks (which is quite likely) metal parts may fly with lethal velocities.

You carry out pressure tests with the system filled with water. If a test with air is unavoidable, e.g., some compressed air systems, then the relevant BS recommends evacuation of the building/area for the duration of the test.

[EricP]

Thanks for this, I had forgotten the energy capacity of air as compared to water.

I will restrict pressure to that required to blow up a kids balloon, which is all required to verify a leak, and the aerosol recommended above to find it.

Cheers