I am pressure testing the drain and vent stack in a new construction and want to know if there is any initial drop in pressure and is 5psi enough to test the system with.Also how long should it stay pressurized.

When we ready a drainage system for inspection we fill the stacks to overflowing the night before and let it set until the inspector passes it. 5 PSI works out to about a little over a 11 foot head. Isn't your stack higher then that? Multiply .434 by the distance between the base and the top of the stack to get the head pressure in PSI. Good luck, tom

Hey CDEFRIA:

Like Tom said, plumbers almost always test the drainage/vent system using water to overflowing the roof vent.

In my area, they also allow for an air test of 5 PSI to be held for 15 minutes minimum... BUT you must use a 5 PSI pressure guage that has increments of 1/10th PSI.

That is my point, and only reason I popped in. Test pressures and testing times vary according to state.. so best is to call your local plumbing inspector and ask him exactly how he wants you to test the system.

Otherwise, 5psi with the correct gauge should be fine... just note that the same test with the wrong gauge may not show the leak

I still recommend testing with water myself!!!

Good luck... MARK

Thank you speedball 1 and massplumber2008