A toilet's sewer drawn on the site plan: M.E.P.flow lays the PVC at a true 2 % fall, keeps the cover, puts the cleanout at the building, drops the tank inlet 100 mm above its outlet and sizes the tank at 3.88 m³. Turn to the section and a 6 L flush reaches the tank in 6.9 s at 1.4 m/s, settles, and the clear effluent runs on to the drain field.