ngle lateral is sufficient. The calculation to confirm this is 4 ft 3 ft = 1.3 or 1 lateral The length of the lateral will be 100 ft minus 6 in. on either end, or 99 ft. Since laterals cannot be longer than 50 ft from the inflow point to the end, the supply pipe must be attached to the lateral at its center, and each leg of the lateral will be 49 ft 6 in. long. Starting with a hole diameter of three-sixteenths inch, a hole spac- ing of 4 ft, and a pressure head at the holes of 3 ft, we see from Table 6.5 that the flow rate per hole will be 0.72 gal per min, and from Table 6.6 we find that we need 1.25-in. diameter laterals. CONVENTIONAL SYSTEM MODIFICATIONS In 99 ft of lateral there will be 99 ft 4 ft = 25 holes The flow will be 0.72 gpm/hole X 25 holes = 18 gpm This flow is below the 25 gal per min minimum flow for a house with fewer than four bedrooms. Therefore, let's go to the next larger hole size (0.25 in.). A 0.25-in. hole will deliver 1.28 gal per min at a 3-ft head. So 25 holes would deliver 1.28 gpm/hole X 25 holes = 32 gpm Let's be very picky and try to get that flow down to around 25 gpm to maybe save a little money on the pump. Let's keep the 0.25-in. holes but extend the hole spacing to 5 ft. 99 ft / 5 ft = 20 holes 1.28 gpm/hole X 20 holes = 26 gpm That's close enough to satisfy an engineer, and we don't have to go to a larger pipe diameter. Our dosing chamber pump will be 5 ft below the ground, and is 82 ft from the trench in the mound. Over that 82 ft, the ground rises 4 ft in elevation. The trench bottom is 2 ft above ground and there are 6 in. of gravel above that. So the total height that the effluent has to be lifted by the pump is 5 + 4 ft + 2 ft + 0.5 ft = 11.5 ft We will use 2-in. supply pipe and 1.25-in. lateral pipe. Table 4.4 will give the associated friction loss. The flow in the supply pipe is 26 gal per min, SO the head loss due to friction is about 1.5 ft per 100 ft. Since there are 82 ft of supply pipe the friction loss is 82 ft X 1.5 ft = 1.2 ft 100 ft 128 ONSITE WASTEWATER DISPOS