Originally Posted by
plumberroy
Peppermint oil if you can seal the opening . someone puts it in and someone else does the smell check . If you can access it and if it is safe to do so you could run the vacuum and run a candle flame near the joints. It will pull the flame towards a leak. You can buy wind indicator at bow hunting supply store that puts out powder it would pull that towards leaks if running. PVC is rated for 5 pounds of air that is what we test sanitary systems at. At higher pressure it can come apart violently
Not a plumber but in this case I'll offer up a suggestion: If you suspect the leak's in a location you can access, try sticking one end of a short length of 1/4" ID vinyl hose lightly into your ear then with the vacuum system pulling a negative pressure use the other end as a 'stethoscope' listening for the sound of sucking as it passes over/nearby the leak.
And a big 'YES IT CAN" to the admonition
not to pressurize PVC DWV pipe over 5 PSI.