Pressure testing JG speed with air?

[macplumb]

Basicly testing new install on a extention today when wet pump gave up on me. So got out trusty compressor and dry test kit. And got stuck in only to be gutted when I had a pressure of 3 bar to zero in five mins. So put pressure back in and went about with leak detector spray but to no avail all fittings sound. Test kit sound tested on some scrap capped copper. And can't se any any probs with pipework.
So basicly could the problem be using air? Managed to test flow with water all was good but when I tested with air there was a drop.
Any ideas

 

[oldplumber]

probably leaking at your commpressor end at the shraeder valve

 

[REDSAW]

long length of pipe and restrictive fittings, air compresses after it has bounced around for a while getting around fittings so drops in pressure.
correct sequence is something like. pressurise to 1bar for 10mins, then 3bar for 90mins. dont quote me on this but you get the jist?.

 

[justlead1]

Hi. Although you would not expect a drop to zero. When air testing the air is heated/warmed via the compressor and should be left to cool within the system, before recording gauge data.

 

[macplumb]

The drop was while I was waiting for stablisation. I expected a drop but 3 bar. Just going to split down sections and narrow down where it is passing.
Just gets me in 12 years had plenty of leaks when testing but they show up some way or another but this one is out to test me. Lol

Found it! Very small leak on 10mm insert for the rad valve must of missed it yesterday. Sometimes it's good to go away and come back with a fresh head.