A. Comply With Standards: All diatomaceous earth type filters, whether of the vacuum or pressure type, shall comply in all respects with the standards of the Uniform Swimming, Pool, Spa and Hot Tub Code covering such filters, and sufficient filtering area shall be provided to meet the design pump capacity as required by the Uniform Swimming Pool, Spa and Hot Tub Code. Diatomaceous earth filters shall be so designed that elements can be hosed down during each washing cycle. Any design which provides the equivalent in washing effectiveness will be acceptable. Where necessary, a hose bib shall be provided in the vicinity of the filter to facilitate the washing operation. (Ord. 11-2-3-71, 5-6-1971; 1997 Code)
B. Rate Of Filtration: The design rate of filtration shall not be greater than 2.0 gpm square feet of effective filtering surface without continuous body feed, and no greater than 2.5 gpm square feet with continuous body feed.
C. Accurate Device: Where body feed is provided, the device shall be accurate to within ten percent (10%) and dependable, and shall be capable of continually feeding within a calibrated range, adjustable from two (2) to six (6) ppm, at the design capacity of the recirculation pump.
D. Filtering Area: Filtering area, where fabric is used, shall be determined on the basis of effective filtering surfaces as created by the septum supports with no allowances for areas of impaired filtration, such as broad supports, folds or portions which may bridge.
E. Materials: The filter and all component parts shall be of such materials, design and construction to withstand normal continuous use without significant deformation, deterioration, corrosion or wear which could adversely affect filter operation.
F. Design And Construction: The filter shall be so designed and constructed, or provision made, to preclude the introduction of appreciable quantities of filter-aid into the pool during precoating operations.
G. Tank Requirements: The tank containing the filter elements shall be constructed of steel, plastic, or other suitable material, which will satisfactorily provide resistance to corrosion, with or without coating. Pressure type filters shall be designed for a minimum working pressure of fifty (50) pounds per square inch with a four (4) to one safety factor. Vacuum type filters shall be designed to withstand the pressure developed by the weight of the water contained therein and closed vacuum type filters shall, in addition, be designed to withstand the crushing pressure developed under a vacuum of twenty five inches (25") of mercury with a safety factor of 1.5 in both instances. The septa of elements which support the filter-aid shall be of corrosion-resistant material. The septa shall be constructed to be resistant to rupture under conditions of the maximum differential pressure between influent and effluent which can be developed by the circulating pump and of adequate strength to resist any additional stresses developed by the cleaning operation.
H. Use Of Dissimilar Metals: Where dissimilar metals, which may set up galvanic electric currents, are used in the filters, provisions shall be made to resist electrolytic corrosion. The filters shall be designed in such a manner that they may be easily disassembled with allowances made for adequate working space above and around the filter to allow the removal and replacement of any part and for proper maintenance.
I. Filter Plant: The filter plant shall be provided with such pressure, vacuum or compound gauges as are required to indicate the condition of the filter. In vacuum type filter installations where the circulating pump is two (2) horsepower or higher, an adjustable high vacuum automatic shut-off shall be provided to prevent damage to the pump by cavitation.
J. Equipped For Cleaning: All filters shall be equipped for cleaning by one or more of the following methods: backwashing, air-bump-assist backwashing, spray wash (mechanical or manual) or agitation.
K. Drainage: Provisions shall be made for completely and rapidly draining the filter. (Ord. 11-2-3-71, 5-6-1971)