Re: Air pressured testing of pipework

Cheers Ed. You've put my mind at ease.

BTW What did you do about the auto bypass requirement on your Keston? (See 'Central heating bypass circuit' thread.)

Thanks

Paul

Through the bathroom towel warmer - 2 locksheilds on the pipework.

I tested the heating circuits I did this way too. Some got left pressurised for weeks, but didn't lose any pressure. (Mostly, I tested at 2 bar because pumping 3 or so radiators up higher than that with a bicycle pump would kill me. As Ed said, air is much less viscous than water, and will leak out at very many times the speed water would.) What does happen though is the pressure changes slightly as the temperature of the pipework changes. If you want to check for this, make sure the temperature isn't changing, or you leave it until the temperature has got back to same value. Don't forget to check all the radiator blanking plugs and bleeding niples with leak detector too. Also, don't assume there are no leaks inside the Keston -- the drain c*ck was leaking in mine where it screwed into a cast elbow, which showed up as an air pressure drop when I was testing -- fortunately easily fixed.

BTW, you get the same effect doing a soundness test on gas piping if it's changing temperature (e.g. if there a length exposed outside and the sun goes in), only it's much more noticable.

The testing of gas pipes is done at two magnitudes less pressure. For the reasons you state there is a one minute settling time before the start of the test to reduce the thermal effects.

With an electronic manometer the last digit is 0.00001 bar if you as much as put a hand on a gas pipe the digits will start to move.