The plumbers installed all of the plumbing lines last week and before they left, they pressurized the lines to 30 PSI. This held the pressure of 30 PSI for about 1/2 day then it dropped to 15 PSI the next day. The PB said they do not use water to pressure test the lines (at this point) in the event they would freeze (yea, we hit 30 degrees this week). How long would you expect to maintain any pressure in the plumbing lines for an air test? Should i be concerned that it dropped to 0 PSI after a 3-4 days?