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Virginia Administrative Code (Last Updated: January 10, 2017) |
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Title 12. Health |
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Agency 5. Department of Health |
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Chapter 590. Waterworks Regulations |
Section 1090. Plant storage
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The applicable design standards of 12VAC5-590-1080 shall be followed for plant storage.
A. Washwater tanks shall be sized in conjunction with available pump units and finished water storage to give the backwash water required. Consideration must be given to the possibility of having to wash more than one filter at a time or several filters in succession.
B. Clearwell storage should be sized, in conjunction with distribution system storage, to relieve the filters from having to follow fluctuations in water use or meet peak demands, including filter backwash water. When finished water storage is used to provide proper contact time for chlorine, special attention must be given to size and baffling. Plant clearwells shall be equipped with a raised viewing port having a clear glass or plastic viewing window and a submerged waterproof electric light.
C. Finished water shall not be stored or conveyed in a compartment adjacent to unsafe water when the two compartments are separated by a single wall.
D. Receiving basins and pump wet wells for finished water shall be designed as finished water storage structures.
E. Hydropneumatic (pressure) tanks may be acceptable in small water systems. When used, they shall comply with the requirements of state and local laws and regulations for the construction and installation of unfired pressure vessels.
1. The tank shall be located above the normal ground surface with the tank end containing the inlet pipe, the pressure gauge and other appurtenances projecting into an operating house to prevent freezing or be completely housed.
2. The tank shall have bypass piping to permit operation of the system while the tank is being cleaned, repaired, or painted.
3. Pressure or level-pressure operated start-stop controls shall be installed on the discharge piping to permit operation of the water supply system.
4. Each tank shall have an access manhole, a drain, and control equipment consisting of pressure gauge, water sight glass, automatic or manual air blowoff, pressure and vacuum relief valves and mechanical means for adding air. Appurtenances to small capacity tanks shall be determined by the division on a case-by-case basis.
5. Tanks and pumps shall be designed to minimize pump cycling and shall have at least the following capacity:
a. When the hydropneumatic tank is fed directly by a well or wells, the effective storage volume is one-third of the hydropneumatic tank's gross volume;
b. When the hydropneumatic tank is fed directly from ground storage, the effective storage volume is the effective volume of the ground storage tank plus the effective volume of the hydropneumatic tank; and
c. At least two booster or transfer pumps are required which have a combined capacity to meet the requirements of 12VAC5-590-690 C.
Historical Notes
Derived from VR355-18-011.02 § 3.46, eff. August 1, 1991.