fourth year
It can only be done by capping all the roof vent lines, and installing a test ball in the sewer outlet from the building. Then the manometer is connected to a point in the drain system and pumped to the one inch level. If there are any leaks in the system, the water level will drop. This test verifies the intregrity of all the trap connections, wax seals, etc., but because of its low pressure does not push through the trap seals.
