Low Pressure Air Test for Sanitary Sewers

Testing a sewer pipe for leakage by using air at pressures of approximately 3 psi can measure effectively the quality of the installation. New work can be tested by noting the time required for pressure in a closed section of the pipe to drop from 3.5 psi to 2.5 psi. Where significant leakage is present, it can be quantitatively determined by metering the amount of air required to maintain a pressure in the test section. The effect of moisture on the permeability of vitrified clay pipe and its effect on the testing procedure is determined. Specifications for testing new pipe installations suggested, and methods of computing time necessary to meet specifications for a single size pipe and for combinations of various size pipes are given. Field tests show that pipe without a detectable failure will lose less than 0.003 cu ft of air per min per sq ft of internal pipe surface, and that any air loss exceeding 2.0 cu ft per min can be located.