(1) Where flushing-valves are used, they shall deliver, automatically, a volume of water not less than, and at a rate not less than, that prescribed for flushing cisterns.

(2) Adequate measures shall be taken to prevent a back siphonage from the soil-water fittings into the water-supply, which measures may consist of either a completely separate tank of sufficient capacity and height to secure satisfactory operation or an anti-siphonage device integral with the valve approved by the local authority.