Mains feeds the lower house direct (metered) and fills the header tanks. The tanks feed the booster set by gravity through two parallel risers (V11 direct, V12 via the strainer); the boosted discharge leaves along the floor through V7 and V2 into the underground main to the houses up the hill. Valve numbers V1–V12 are proposed labels. Still to record: pressure-switch set points, pump 2 plate, vessel plate, tank capacity, and which riser is normally in use.