Recently witnessed a pressure test followed by the leakage test.  Pressure dropped from 161psi to 159psi for 5,710 ft of 8-inch DI pipe.  Is there a way for me to verify the leakage (7.5 gal) theoretically? 
I'm suspicious of the leakage number because they pulled the suction line out of the water tank used to pump the line up....and I suspect air got in the suction line and messed with the test. The pressure test criteria does allow you an allowable which can be calculated in the above formula. At the end of the test you are allowed to pump an additional 4.34 gallons back into the line to bring it back to the test pressure. Typically in the northeastern U.S. I have been required to hold between 150 psi - 200 psi anywhere from 1 hour to 2 hours and everwhere in between. Once completed, if I have dropped below the test pressure, I am allowed to pump in the allowable leakage in Chemical pumps, calculated above, back into the line to get back to the test pressure. If it does not pump back up, you fail. If you pumped in an additional 7.5 gal then it appears to me that you failed. Keep in mind everywhere I have done a pressure test the rules and regulations have been different! Same basic idea but everyone seems to have there own take.

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