Altitude Valves. Provide an altitude valve that can,
in winter, be set to keep the high water level at minimum of 3
ft below the overflow, thus preventing floating ice from
damaging the tank roof when lifted by rising water.
Corrosion Protection . Refer to MIL-HDBK-1004/10,
Electrical Engineering Cathodic Protection and AWWA D102,
Coating Steel water-Storage Tanks.
Pollution . Protection against pollution should be
accomplished as discussed below.
Roof . Cover all tanks and reservoirs with roofs to
preservation may contain arsenic or other toxic chemicals.
Ground. To divert the surface runoff, grade and drain
around ground storage and underground storage tanks.
Vents. To keep out insects and rodents, provide
20-mesh bronze insect screens over all vent openings. The vents
should be rainproofed by using Goose necks or vent caps.
Underground Storage Tanks . These tanks should have
Vaults and Valve Chambers .
These chambers should be
watertight or self- draining.
Provide structural and operational safety.
Vent. Adopt a size to relieve the air pressure
caused by the change of water level. Maximum air velocity
through the opening area should not exceed 1,000 fpm. Design
the screen so that, if clogged by insects or frost, it will
either swing on hinges or collapse before allowing damage to the
Provide a minimum capacity equal to
the maximum inlet flow.