(A) Recirculation systems shall contain rapid pressure filters of either the sand and gravel type, the diatomaceous earth type or an approved equal. Sufficient filter area shall be provided to filter the entire contents of the pool in 18 hours at the rate of not more than five gallons per square foot of filter area per minute for sand and gravel filters and not more than three gallons per square foot of filter area per minute for diatomaceous earth filters. Filter tanks shall be built for a minimum of 50 pounds working pressure and shall be supported in a manner to prevent tipping or setting.
(B) The recirculating pump shall have sufficient capacity to backwash at a minimum rate of 12 gallons per minute per square foot of surface area.
(C) The filter system shall be equipped with the following:
(1) A pressure gauge on the influent piping;
(2) A pressure gauge on the effluent piping;
(3) A method of releasing the air at the top of the filter;
(4) A backwash sight glass that can easily be removed for cleaning; and
(5) An access head or hole large enough to permit inspection, maintenance and rapid work.
(D) A hair and lint catcher shall be installed on the suction side of the circulation pump to prevent hair, lint and other extraneous matter from reaching the pump and filters. Hair and lint catchers shall be so designed that they can be easily dismantled for cleaning and inspection and shall be so located as to be easily accessible for cleaning. The design features shall be as follows: Water passes through the strainer from the outside; the strainer is made of noncorrosive material; the width or diameter of strainer openings is not more than one-eighth of an inch; and the area of the strainer opening is at least five times the cross-sectional area of the inlet pipe to the strainer.
(E) Pool piping shall be sized to permit the rate flows for filtering and backwashing without exceeding the maximum head at which the pump will provide such flow. In general, the water velocity in the pool piping shall not exceed 10 feet per second. The recirculation piping and fittings shall meet the following requirements.
(1) The inlet fitting shall be located so as to discharge below the pool overflow level.
(2) An outlet shall be placed at the deepest point in every pool for recirculating and emptying the pool.
(3) A vacuum inlet fitting shall be located in an accessible position below the water line.
(4) Pool recirculation piping passing through the pool structure shall be of copper compound.
(5) A minimum of one recirculation system inlet shall be provided for every 800 square feet or fraction thereof of surface area of rectangular or oblong shaped pools, and a minimum of one recirculation system inlet shall be provided for every 615 square feet or fraction thereof of surface area of kidney-shaped or L-shaped pools.
(6) Inlets shall be placed so as to produce, so far as possible, uniform circulation of water throughout the pool.
(7) A minimum of one recirculation system outlet shall be provided for every 800 square feet or fraction thereof of surface area of all private pools.
(8) Pools shall be equipped with facilities for completely emptying the pool and the discharge of pool water.
(2000 Code, § 15.88.110)