(a) The recirculation system shall be equipped with a filtration system that is NSF International listed, or the equivalent, and will filter the entire water volume of the swimming pool within the required turnover time specified in Section 838.33(b). Filtration equipment shall be operated continuously, twenty-four hours per day. Valves shall be provided at appropriate locations to allow the isolation and maintenance of equipment. Filter components which require servicing shall be accessible for inspection and repair and installed according to the manufacturer's specifications and recommendations. All pressure systems shall be provided with a manual or automatic means to permit the release of air which may accumulate within the filter tank. Design criteria for the indicated type of filters shall be as follows:
(1) High-rate filter. A filter utilizing a media capable of filtration at a high rate of flow. The rate of flow shall not be less than five gallons per minute per square foot of filter surface area, and not greater than twenty gallons per minute per square foot of filter surface area. The backwash rate of flow shall be at the rate specified by the manufacturer.
(2) Diatomaceous earth filter. A filter utilizing diatomaceous earth as a filter media.
A. Pressure or vacuum type. A diatomaceous earth filter through which the rate of flow does not exceed one and one half gallons per square foot of filter surface area.
B. Pressure or vacuum with slurry feeder. A filter that is equipped with a feeder that continuously feeds a diatomaceous earth suspension and has a rate of flow not exceeding three gallons per minute per square foot of filter surface area.
C. Separation tanks or a sump pit with a stand pipe shall be installed to collect spent diatomaceous earth so that it can be collected and disposed of in an approved manner. Alternative methods for diatomaceous earth collection may be approved by the Director. When using diatomaceous earth filters with separation tanks, the separation tank shall be provided with a means of release or a lid which provides a slow and safe release of pressure and shall have a readily visible precautionary statement affixed that warns the user that the air release must be opened before opening the separation tank.
D. Piping and valves shall be provided for all diatomaceous earth filters to allow for a pre-coat cycle that re-circulates water directly from the outlet to the inlet of the filter without returning to the swimming pool.
(3) Rapid sand filters. A filter utilizing sand as the filter media, with a filtration flow rate not exceeding three gallons per minute per square foot of filter area. In sand filters, the layer of filter sand shall be at least 20 inches in depth, properly supported by uniform layers of clean graded gravel to a minimum depth of 12 inches or supported by porous plates. The filter sand shall have an effective size of between 0.45 and 0.55 millimeters with a uniformity co-efficient not greater than 1.7. In anthracite coal filters, the anthracite shall have a depth of at least 24 inches and shall have an effective size between 0.6 and 0.8 millimeters with a uniformity co-efficient of not greater than 1.8. The backwash rate of flow shall be four times the filtration rate.
(4) Cartridge filters. A cartridge filter through which the rate of flow does not exceed the design rate or a maximum of three hundred seventy-five thousandths gallon per minute per square foot of filter surface area. Cleaning of cartridge filters must be in accordance with the manufacturer's recommendations. One complete extra set of cartridges shall be available at all times to facilitate cleaning.
(5) Other filtration systems whose performance equals or exceeds those described above may be used in a pool recirculation system with the approval of the Director.
(b) Gauges and Flow Meters. The filter system shall be provided with a minimum of one influent pressure gauge for each filter and one effluent pressure gauge following the filter system. Recirculation system pumps shall be fitted with a vacuum and pressure gauge installed as near as practical to the pump suction and discharge pipe connections. All pressure gauges shall measure pressure directly in pounds per square inch (psi). Vacuum gauges shall measure in inches of mercury. The system shall have a flow meter on the return line to measure the flow of filtered water being returned to the swimming pool and a flow meter to measure the rate of backwash in sand or anthracite coal filters. The flow meter shall be of fixed calibration, shall measure in gallons per minute, and shall be properly sized to indicate the design rate of flow at approximately mid-scale. Gauges and flow meters shall be readily accessible and clearly visible, shall be in good repair, and shall be located and installed according to the manufacturer's specifications and recommendations.
(Ord. 07-14. Passed 12-18-07.)