ice ring several inches thick may form inside elevated tanks, especially if water
circulation is slow. In the spring, the ring melts loose from the tank sides and floats to
the top of the water. The top of the ice ring is then considerably higher than the water
surface. To keep the ring from damaging the top of a closed tank or projecting above
the top of an open tank, set altitude valves to maintain a freeboard of at least 14
percent of the tank depth during the winter.
Corrosion Prevention. For methods of preventing corrosion in
tanks and standpipes, see par. 11.9.2. Even though cathodic protection prevents
corrosion below the water surface, when it is used, the complete interior of the tank roof
and exterior need other protection, such as periodic painting.
Pneumatic Tanks. While the operation of these units is usually automatic,
the operator is responsible for operating pressure equipment effectively. It is important
to see that the air cushion is maintained at all times. Air may be depleted by leaks and
by dissolving in the water. Consult the manufacturer's instructions for methods of
starting, stopping, and operating this pressure equipment.
Maintaining Storage Facilities. Guidance on specific maintenance
procedures and paint systems applicable to water storage facilities can be found in
Water Storage Facility Safety
In general, only trained and experienced operators should be
allowed to work on elevated and ground-level storage tanks and standpipes. This work
is hazardous and dangerous for untrained workers. Special precautions are also
needed for work on or in tanks. In these confined working areas, workers need to
guard against slipping or falling from dangerous heights. Refer to Occupational Health
and Safety Act (OSHA) Part 1910.146, Permit-Required Confined Space, and to
The following guidelines apply to working in and around storage
Read, understand, and follow all applicable safety
directives, including those pertaining to confined-space entry.
Check the security of ladders frequently. Provide required
safety cages or safety cable equipment.