Originally Posted by Joelk
Perhaps your design is different, but the leakdown tester I have, and others I have seen used, work on the percentage difference between the guages.
If the one guage reads 100 PSI and the other 90 PSI, that is 10% leakdown.
If the one guage reads 120 PSI and the other 90 PSI, that is 25% leakdown.
The instructions with my leakdown tester recommend setting the one guage at 100 PSI to keep the math simple.
Thats correct. The 2nd gauge reads the % of leakage based on the supply psi. 90/100= 10% 67.5/75= 10% 45/50=10%
Use whatever air pressure YOUR system can maintain.