Every swimming pool shall be equipped with a pressure sand filter or an approved equal. Filters will be approved if certified tests from an independent testing laboratory are submitted to the building inspector indicating that the filter tested is equal to the pressure sand filter in the following:
(1) 
Clarity of effluent;
(2) 
Dirt-holding capacity and length of filter cycle;
(3) 
Durability of material.
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-26)
(a) 
The filter system shall have sufficient capacity to provide a complete turnover of the pool water in eight (8) hours or less, when operated at a rate not to exceed three (3) gallons per minute per square foot of filter area.
(b) 
The recirculating pump shall have sufficient capacity to backwash the filter at a rate of at least ten (10) gallons per minute per square foot of filter area, when operating against the total head of the backwash system. The pump motor shall not be operated at overload which exceeds the service factor.
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-27)
Pool pumps shall be equipped on the inlet side with an approved type hair and lint strainer. The basket of the strainer shall be non-corrosive and shall have an open screen surface of at least ten (10) times the cross-sectional area of the inlet pipe.
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-28)
(a) 
Size of Sand.
Filter sand shall be a hard, uniformly graded silica material with effective particle sizes between 0.45 and 0.55 millimeters in diameter with uniformity coefficient of 1.45 to 1.69. There shall be no limestone or clay present.
(b) 
Depth of Sand.
Filter sand shall be no less than nineteen (19) inches in depth with a freeboard of no less than nine (9) inches or no more than twelve (12) inches.
(c) 
Grades of Rocks.
There shall be no less than four (4) grades of rock which shall be clean, noncrushed, rounded noncalcareous material.
(d) 
Depth of Rock Bed.
The total depth of the rock-supporting bed shall be no less than fifteen (15) inches and each grade shall be two (2) inches or greater in depth. Each layer of rock shall be leveled to prevent intermixing of adjacent grades.
(e) 
Size of Layers.
The top layer shall vary in size between one-eighth (1/8) inch and one-fourth (1/4) inch. The next layer shall vary in size between one-fourth (1/4) inch and one-half (1/2) inch. The next layer shall vary in size between one-half (1/2) inch and three-quarter (3/4) inch. The bottom layer shall vary in size between one (1) inch and one and one-half (11/2 ) inches.
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-29)
Filter tanks shall be built for a minimum of fifty (50) pounds working pressure with a safety factor of four (4). The filter under drain shall have an effective distribution of at least twenty-five (25) percent of the cross-sectional area of the tank. Tanks placed underground shall be steel plate at least three-sixteenths (3/16) inch in thickness, with an approved noncorrosive exterior coating. Filter tanks shall be supported in a manner to prevent tipping or settling.
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-30)
Operating instructions shall be posted on every filter system and all valves shall be properly designated with metal tags indicating purposes or methods of use.
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-31)
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 if the backwash discharge outlet to the receptor is not visible from the backwash control valve. (Sight glass shall be installed adjacent to the backwash control valve.)
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-32)
Pool piping shall be sized to permit the rated flows for filtering and backwashing without exceeding the maximum head at which the pump will provide such flows. In general, the water velocity in the pool piping should not exceed ten (10) feet per second. The recirculating piping and fittings shall meet the following requirements:
(1) 
The vacuum inlet fittings shall be located in an accessible positions below the water line.
(2) 
An outlet shall be placed at the deepest point in every pool for recirculation and emptying the pool.
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-33)
Fullway valves shall be installed to insure proper functioning of the filtration and piping system as follows:
(1) 
A valve shall be installed on the main suction line located in an accessible place outside the wall of the pool.
(2) 
Valves up to, and including two (2) inches in size, shall be brass. Sizes over two (2) inches may have cast-iron or brass bodies. All working parts of valves shall be of noncorrosive material.
(3) 
Combination valves may be installed if the materials and design comply with the intent of this article.
(1974 Code of Ordinances, Chapter 28 1/2, Sec. 28 1/2-34)