Section P-808 Water Supply Tanks

A water supply system shall be supplemented from a gravity house tank, pressure tank, or booster pump system when the water pressure from the public water main or other potable water line is insufficient to supply the fixtures of the water supply system which are likely to be in simultaneous operation at the residual pressures specified in Section P-811.1.

All potable water supply tanks shall be properly covered or sealed to prevent the entrance of foreign or contaminating material into the water supply. Soil or waste lines shall not pass directly over non-pressure water supply tanks or over manholes in pressure tanks.

A potable water supply tank from which water for human consumption is drawn shall not be lined, painted, or repaired with any material which may affect either the taste or potability of water supplied from such tank when the tank is returned to service. Tanks shall be disconnected from the water distribution system whenever necessary to prevent a foreign fluid or substance from entering such system during any such operation or from any other source.

After a potable water supply tank has been installed, cleaned, painted or repaired, it shall be disinfected by filling it with a solution containing 100 ppm of available chlorine and allowing it to stand for two hours before the tank is flushed and returned to use.

All water pipes, water tanks, and water-supplied appliances and devices subject to freezing temperatures shall be effectively protected against freezing.

Overflow outlets for gravity tanks shall not be less than 4 inches below the tank supply and shall discharge at least 6 inches above a roof or within 6 inches of a floor drain or they shall discharge over and above the flood level rim of an open water supplied sink or other approved receptacle having a trap with a diameter equal to that of the overflow pipe.

Overflow pipes shall be properly screened against the entrance of insects or vermin.

Overflow outlets shall terminate in a horizontal position above a roof or in a turned-down position above a sink or receptacle.

Overflows shall be sized as specified in Table P-808.

TABLE P-808 —
WATER SUPPLY TANK DRAINS AND OVERFLOWS

Tank Capacity (Gallons)	Minimum Size Drain Pipe (Inches)	Minimum Size Overflows
Up to 750	1-1/4	One size larger than supply pipe
75 to 1500	1-1/2
1501 to 3000	2
3001 to 5000	2-1/2
5001 to 7500	3	One size larger than supply pipe (Minimum size 4")
Over 7500	4

All water supply tanks shall be provided with valved drain lines located at or near their lowest point and discharged as an indirect waste or as required for overflow pipes in Table P-808. Each tank shall be provided with pipes of diameters specified in Table P-808. Each drain shall be equipped with a gate valve or ball valve of the same diameter as the pipe.