# Sec. 22-126. Construction Specification Codified through Bill No. CB-018-2026, adopted May 12, 2026, effective July 24, 2026. Source: Municode, Supplement 2026 Update 2. Editorial notes and legislative history omitted. ## Sec. 22-126. Construction Specification Prince George's County, Md., Code ยง 22-126 (2026) (a) Individual sewage disposal systems must be designed, constructed, altered, extended or enlarged, or remodeled in accordance with the requirements set forth in this Subdivision. (b) The building sewer shall be constructed in accordance with the Washington Suburban Sanitary Commission plumbing regulations. (c) Septic tanks shall meet the following specifications: (1) The septic tank shall have a capacity of not less than that shown in Table 5 (Section 22-156). (2) In tanks having two (2) compartments, the inlet compartment shall have a capacity between one-half (1/2) and two-thirds (2/3) of the total tank capacity. If an inverted fitting is used on the inlet compartment side of the baffle, its opening shall be located forty (40) percent of the liquid depth below the flow line. In each case, the total area of the opening provided by the pipe fitting shall be equal to, or greater than, the area of the inlet to the tank. (3) Septic tanks shall be constructed of reinforced concrete, or other material approved by the Health Officer, and be of permanent construction. Precast concrete tanks should have a minimum wall thickness of three (3) inches and should be adequately reinforced. The cover of the tank shall be designed for a dead load of not less than three hundred (300) pounds per square foot and, if of concrete, should be reinforced and not less than three (3) inches thick. Septic tanks which are subject to vehicular loadings shall be constructed of reinforced concrete adequate to withstand the loadings. (4) The inlet and outlet of the septic tank shall be provided with manholes. Each compartment in multiple compartment tanks shall be provided with a manhole. Manhole openings shall be at least twenty (20) inches in minimum dimension and provided with covers which can be sealed watertight. Manhole extensions shall be required where necessary to provide access for maintenance to the septic tank and be so constructed to be watertight. (5) Pipe inlets shall be installed consisting of a sanitary tee of cast iron, PVC, or other material as authorized by the Washington Suburban Sanitary Commission plumbing regulations. Outlets may be sanitary tees of cast iron, vitrified clay pipe, plastic or other acceptable material. Short sections of pipe shall be installed in the tees to the required outlet depths. Baffles may be installed when approved by the Health Officer. (6) The invert of the inlet pipe shall be located at least two (2) inches above the invert of the outlet. (d) Construction Standards for Absorption Trenches. (1) The minimum absorption trench length shall be calculated according to Appendix A (Section 22-150). (2) The trench shall be filled with filter material to a level two (2) inches above the distribution line. The filter material shall cover the tile and extend the full length, width and depth of the trench and be not less than six (6) inches below the tile and two (2) inches over the tile. The filter material shall be washed gravel or other material approved by the Health Officer ranging in size from one and one-half (1 1/2) to two and one-half (2 1/2) inches. The filter material shall be reasonably free of fines, dirt, clays and other associated material and shall be covered by untreated paper or similar material one (1) foot from the top of the ground. (3) Distribution lines in absorptive trenches shall be constructed of ridged perforated plastic pipe that shall meet National Sanitation Foundation (NSF) Standard 14 or other material approved by the Health Officer. Each pipe must sustain a minimum pressure of twenty-five (25) psi and must have a minimum of three (3) rows of perforations with each row having three (3) perforations of three-quarter (3/4) inch diameter per lineal foot. The invert of each distribution line shall be installed approximately eighteen (18) inches below ground grade. (4) Absorptive trenches with depths of three (3) feet or less shall not be constructed on ground having a slope greater than ten (10) percent. Absorptive trenches with depths of greater than three (3) feet, but less than five (5) feet shall not be constructed on slopes exceeding fifteen percent (15%). Absorptive trenches with depths of five feet or greater shall not be constructed on ground with slopes in excess of twenty-five percent (25%). (5) All absorptive trenches shall be constructed at the same depth as the percolation test. (6) Absorption drainfields depths of less than five (5) feet will be spaced according to Table 6 (Section 22-157). Absorption drainfields depths of five (5) feet or greater will maintain a spacing of twice the gravel depth between drainfields up to a maximum of twenty (20) foot separation. (7) The distribution lines within one (1) absorption trench shall not exceed one hundred (100) feet in length. A one percent (1%) slope shall be maintained on the first twenty (20) feet of pipe while the remainder of pipe should maintain zero percent (0%) slope. (e) Seepage Pits; specifications. (1) Absorptive area. Seepage pits may be installed where the absorptive strata is seventeen (17) feet or greater below grade. (2) Location. Seepage pits shall not be located in swales or ravines and shall not be installed on slopes exceeding twenty-five percent (25%). (3) Number of Pits. The number of pits shall be calculated based on the equivalent length of drainfield as determined by Appendix A (Section 22-150). (4) Depth of Excavation. The seepage pit excavation shall be constructed to the depth of the percolation tests. (5) Seepage pits shall be separated a minimum of twenty (20) feet from center to center. (6) The general construction of seepage pits shall be in accordance with Figure 1 (Section 22-158).