(1) Filtration equipment shall be provided on all pools, spas, and other water features and shall be installed and maintained in accordance with the manufacturer's specifications. Filters shall be sized to accommodate or exceed the design flow rate of the system.

(2) Filters shall be designed so that filtration surfaces may be easily inspected and serviced.

(3) A flow rate indicator shall be provided and installed in a manner that shows the recirculation rate of the pool, spa, or other water features. The indicator shall measure the rate of flow through the filtering system with an appropriate range readable in gallons per minute and that is accurate within ten percent of actual flow.

(4) Flow meters shall be installed in a straight section of the piping unless the manufacturer's guidelines require the flow meter to be installed in some other location. There shall be straight pipe upstream and downstream from the location of the flow meter. The upstream pipe section must be a minimum of ten pipe diameters in length. The downstream straight pipe section must be a minimum of four pipe diameters in length.

(5) Filters shall comply with the requirements of ANSI/NSF 50-2008.

(a) The maximum flow rate for different types of filters may not exceed the requirements of ANSI/NSF 50-2008. The maximum application rate for sand filters shall not exceed 15 gallons per square foot of media, unless a higher rate is specifically approved by the manufacturer for commercial use.

(b) Filters shall be fitted with both influent and effluent gauges.

(6) For cartridge type filters, a minimum of three filters must be provided for each pool, spa, or other water feature:

(a) one in use;

(b) one which has been cleaned and is ready for use; and

(c) one which is being cleaned.

(7) For sand-type filters, whether of the gravity or pressure type, including high-rate filters, the filter system shall be provided with an influent pressure indicator and an effluent pressure indicator to show the condition of the filters. The filter system shall include an air relief device at or near the high point of the filter. A sight glass shall be provided on the back-wash discharge line.

(8) For diatomaceous earth type filters, whether of the vacuum or pressure type:

(a) the filter shall be designed, constructed, and operated to preclude the introduction of appreciable quantities of filter-aid into the pool, spa, or other water feature during pre-coating operations; and

(b) the filters shall be designed and installed with adequate working space provided above and around the filter to allow the easy removal and replacement of any part and for proper maintenance.