On Sat, 02 Dec 2006 15:35:32 +0000, Ian Stirling wrote:

Doctor Drivel wrote:

"Moz" wrote in message
...

About 40 years ago my Dad pressure tested a DIY plumbing installation
using a car tyre valve (soldered somehow into a 1/2 inch BSP
compression fitting), a foot pump and a car engine compression gauge.
After filling the system with compressed air he left it overnight and
checked for pressure drop.
Does anyone know if this would be an appropriate way to test a plastic
(JG Speedfit) central heating system prior to filling (the gas fitter
is coming to fit the boiler on Tuesday)? I can seal off the open ends.

No. Never test with compressed air. If a fitting fails it can shoot off like
a rocket and seriously hurt.

Yes, it can - some care is needed.

For maybe a bar of pressure, you've got 4Kg of force on a 22mm fitting.
Over 3cm, this'll accellerate a 100g fitting to maybe 20m/s, if it comes
completely loose, and has no attachment to the pipe at all.

Don't stand anywhere a fitting could fly.

Agreed. My own rule is that I pump with air to about 1/2 bar. If you can
get that far then nothing has been forgotten. I'll then go up a little
further say to 0.7 bar and leave it a while. If it holds pressure for 15
minutes then the air is released slowly (bleed valves) and the water is
used. The only other way I can then have a puddle is when there is a joint
that's not fully taken but the flux is holding it sound when cold.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards