unified monitoring system of the subject invention pipe 1 shall be 6 inch diameter polyvinyl chloride drain pipe with solvent cemented joints or gasketed fittings the verticalpipes 2 shall be 4 inch or 6 inch diameter polyvinyl chloride drain pipe with solvent cemented joints or gasketed fittings perforations in pipe 1 shall be circular and 1 4 34 u00b1 1 16 34 in diameter the holes should be arranged in rows parallel to the axes of the pipe 1 and shall be spaced approximately 3 inches center to center along the rows there shall be four rows of perforations composed of arranged as two rows of holes on each side of pipe 1 the lower row of holes is set at the intersection of the limbs of a 90 degree angle with the wall of the pipe 1 measured from the center of the pipe the upper row of holes is set at the intersection of the limbs of a 160 degree angle with the wall of the pipe 1 thus one row of perforations holes on each side of the pipe 1 shall be 10 degreesdown from the horizontal axis or plane passing through the center of the pipe 1 the second and lower row of perforations holes one row on each side of pipe 1 shall be 45 degrees down from the horizontal axis.