A = p × Vp x 0.20 for package sewage treatment plants where p is the number of people served by the tank (this should be the maximum number of people that could live in the house).
A = p × Vp x 0.20 ar gyfer gweithfeydd trin carthion lle mae p yw nifer y bobl a wasanaethir gan y tanc (sef y nifer fwyaf o bobl a allai fyw yn y tŷ).