in a bed, lateral spacing is usually 3 ft between laterals. Laterals are generally at least 1.5 ft from the bed sides. To find the number of laterals necessary, divide the bed width by 3 ft, ignoring any fractional remainder. For example, a 10-ft-wide bed would need 10 ft =3.3 or three laterals. One would run down the center of the bed and the other two would be 3 ft away on either side. The maximum number of laterals is usually considered to be three, which would be six lateral "legs" with a central manifold, or a loop with a central lateral down the length of the bed at its center. ONSITE WASTEWATER DISPOSAL Hole diameter in the lateral distribution pipes should be at least one-eighth inch. If you don't shave off the burrs on the inside of the pipe that result from drilling these holes, you can be sure that the holes will plug up. A hole diameter larger than one-eighth inch is recommended to minimize the chances of plugging. Three- sixteenths to five-sixteenths inch holes are the smallest size holes commonly used. Holes much larger than three-eighths inch in diameter can result in uneven distribution or the need for a large pump. Too much effluent delivered too fast can result in seepage out of the mound sides. Hole spacing may be from 2 ft to 6 ft. Choose 4 ft for a place to start the calculations. The number of holes per lateral is calculated as follows: No. of holes per lateral = length of lateral (ft) hole spacing (ft). In addition to the holes in the underside of the lateral, if the mound is downhill from the bottom of the dosing chamber, there must be a one-quarter inch hole drilled in the bottom of the supply pipe just before it exits the dosing chamber (Figure 4.6). This hole is to assure that the contents of the dosing chamber will not siphon to the mound after the pump shuts off. When the pump is running, about 2 gal per min will be pumped through this hole and back into the dosing chamber. Pressure head is the amount of pressure pushing on the water, and it is measured in feet of water or in pounds p