(a) Each pipe associated with a sludge processing unit must have a slope that ensures the flow of sludge.(b) A pipe under a stationary structure must allow a blockage to be easily eliminated by rodding or a sewer-cleaning device.(c) A gravity pipe must have uniform grade and alignment.(d) The slope of a gravity discharge pipe must not be less than 3.0%.(e) The minimum diameter for a pipe associated with sludge processing is shown in Figure: 30 TAC §217.243(e):Attached Graphic(f) The available head on a discharge using a gravity withdrawal pipe must be at least 4.0 feet.(g) A gravity withdrawal pipe from a clarifier must allow for the removal of sludge.(h) Each sludge pipe must include a means to observe the quality of the supernatant from each of the withdrawal outlets.(i) Each individual sludge processing unit must have a dedicated means of dewatering.(j) Pipes located inside a digestion tank must be designed for use in corrosive environments and must be sufficiently supported to prevent damage to the pipe or adjacent equipment.(k) A sludge pipe must not contain any bends that form an acute angle with the pipe.