§ 20-14. Filtration equipment.

All family swimming pools shall be equipped with filtration equipment as follows:

(1)

Sand filters shall have a filtration rate not to exceed five (5) gallons per minute per square foot of filter area and a minimum backwash rate of twelve (12) gallons per minute per square foot of filter area. Filtering material shall consist of not less than nineteen (19) inches of suitable grades of screened sharp silica filter sand properly supported on a graded silica and/or granite gravel bed, with the effective size of the particles of sand 0.4 to 0.5 mm with a uniformity coefficient of 1.5 to 2.0. There shall be sufficient free board above the surface of the sand to overflow troughs or pipes of the filter to permit a fifty-percent expansion of the sand during backwash cycle without loss of sand. Sand filters shall be provided with pressure gauges on the influent and effluent lines and sight glass on the backwash line. The filter tank shall be of sheet steel construction either riveted or welded, hydrostatically tested to a pressure of fifty (50) psi minimum. An inlet baffle and an indirect underdrain shall be provided. Tanks placed underground shall be steel at least three-sixteenths inch in thickness with noncorrosive exterior coating. A manhole, eleven (11) inches by fifteen (15) inches minimum, and cover shall be provided on tanks twenty-four (24) inches or larger.

(2)

Pressure- or vacuum-type diatomaceous earth filters may be used, providing the manufacturer's recommendations for filtration rate are not exceeded and that three (3) gallons per minute per square foot of filter area is not exceeded. All diatomite filters shall have provisions for removing the filter cake by either backwash or by disassembly. Pressure filters shall be provided with a pressure gauge.

(3)

Other types of filtration equipment may be used if approved by the building inspector. The minimum backwash rate shall be twelve (12) gallons per minute per square foot of filter area.

(Code 1959, § 20A-15)