(a) General.

1. (1) Filter required.

   1. (A) All pools/spas shall be equipped with a filtration system for the purpose of clarifying the water.
   2. (B) The filtration system shall be an integral part of the circulation system and shall consist of:

(i) Sand-type filters;

1. (ii) DE type filters; or

   1. (iii) Cartridge filters.

2. (2) Design.

   1. (A) All filter units shall be designed and constructed in accordance with applicable NSF/ANSI standards pertaining to swimming pool/spa filters.
   2. (B) The filter system shall be designed and installed with all the necessary valves and piping which may be needed to isolate, backwash, or drain an individual filter unit for maintenance and/or repair.
3. (3) System capacity. The filtration system shall have the capacity to meet the flow rate required for the prescribed number of turnovers without exceeding the maximum allowable filtration rate.
4. (4) Rate of flow control. All filter installations shall be equipped with a rate of flow control valve (ball, gate, and other control valve types) on the discharge side of the pump.

5. (5) Accessibility. All filters shall be designed and installed so as to provide easy accessibility for:

   1. (i) Cleaning;

      1. (ii) Operating;
      2. (iii) Maintaining; and
      3. (iv) Servicing.

6. (6)

   1. (A) Gauges. Filters shall be equipped with an approved pressure gauge or gauges.
   2. (B) Vacuum filters shall be equipped with a vacuum gauge or gauges.
7. (7) Drainage. All filters shall be designed and installed with all the valves and piping needed to drain the filters completely for servicing or winterizing.
8. (8) Bypass. Provisions shall be made to bypass the filter and empty the pool water to waste.

9. (9) Air relief.

   1. (A) All pressure filters shall be designed and installed with an air relief valve or valves which shall be located at or near the high point of the filters and be capable of being operated manually.
   2. (B) Automatic air-relief valves on top of the filters with manual air-relief capabilities are acceptable.

10. (10) Filter backwash.

    1. (A) Backwash from the filter or filters shall be piped to a sanitary sewer or other disposal method approved by the Department of Health.
    2. (B) If required, a permit for the discharge shall be obtained from the Division of Environmental Quality.
    3. (C) In all cases of filter backwash discharge, an air-gap shall be provided with a minimum of six inches (6”) between the discharge pipe and top of the sump or sewer piping.
    4. (D) Both the sump and the exit pipe shall be sized to accommodate the backwash flow.
    5. (E) A sight glass or other means for viewing the clarity of the backwash shall be provided.
    6. (F) A provision to filter to waste shall be provided.

(b) Sand filters.

1. (1) General.

   1. (A) When a sand-type filter or filters is installed, it may be either a gravity, or a pressure, or a vacuum sand-type filter.

   2. (B) Options include:

      1. (i) Rapid-rate sand-type filter, which shall be designed for filtration rates not in excess of three gallons per minute per square foot (3 gpm/sq. ft.) of sand bed area; or
      2. (ii) High rate sand-type filter, which shall be designed with filtration rates not in excess of:

(b) (b) Fifteen gallons per minute per square foot (15 gpm/sq. ft.) of sand bed area on newly constructed pools using a six-hour turnover rate.

1. (C)

   1. (i) All other pool/spas may utilize the fifteen gallons per minute per square foot (15gpm/sq. ft.) of sand bed area rate.

      1. (ii) See 20 CAR § 136-108(b) for turnover rates.

2. (2) Single filter flow control.

   1. (A) If a single filter unit is provided on pools designed and constructed prior to December 2003, the pump shall be sized at fifteen gallons per minute per square foot (15 gpm/sq. ft.) of filter area to provide the necessary backwash flows.
   2. (B) A valve to control flow shall be provided to limit the normal filtration rate to seven and five-tenths gallons per minute per square foot (7.5 gpm/sq. ft.) of filter area.
   3. (C) Flow control valves shall be required on existing facilities utilizing single sand filters on a seven and five-tenths gallons per minute per square foot (7.5 gpm/sq. ft.) rate.
   4. (D) Any filter renovation of pools prior to 2003 will require preliminary review to determine existing piping size and design considerations.
3. (3) Multiple filters. If two (2) or more filters are used to achieve the required filter area, they must be of the same size.
4. (4) Inspection port. Internal components of the filter shall be accessible through an inspection port as required by NSF.
5. (5) Backwash. When a sand-type filter is installed it shall be designed and installed such that it may be backwashed at a rate of no less than fifteen gallons per minute per square foot (15 gpm/sq. ft.) of filter bed area.

6. (6) Filter media.

   1. (A) Filter sand shall be hard filter silicon material free of carbonates or other foreign material, with:

      1. (i) An effective particle size of between four tenths millimeters (0.4 mm) and fifty-five hundredths millimeters (.55 mm); and
      2. (ii) A uniformity coefficient not exceeding one and seventy-five hundredths (1.75).
   2. (B) Depth of filter sand shall be adequate for the function intended.

   3. (C) In no case shall it be less than:

      1. (i) Twenty inches (20”) for rapid-type filters; and
      2. (ii) Twelve inches (12”) for high-rate type filters.

7. (7) Freeboard. A freeboard between the top of the filter media and the lowest draw off point of the upper distribution system shall be provided and be of sufficient height so no media is lost during backwash.

   1. (c) Diatomaceous earth filters.

8. (1) Filter type.

   1. (A) When a DE type filter is installed, it may be:

      1. (i) Either a pressure or a vacuum type; and
      2. (ii) Designed to operate either with or without continuous slurry feed.
   2. (B) A DE filter with a continuous slurry feed shall be used for filtration rates not in excess of two and five-tenths gallons per minute per square foot (2.5 gpm/sq. ft.) area.
   3. (C) A DE filter which operates without continuous slurry feed shall be used for filtration rates not in excess of two gallons per minute per square foot (2 gpm/sq. ft.) of filter area.

9. (2) Cleaning.

   1. (A) When a DE filter is installed it shall be designed and installed with provisions for cleaning by one (1) or more of the following methods:

      1. (i) Backwashing;
      2. (ii) Spray wash (either mechanical or manual); and
      3. (iii) Agitation.
   2. (B) The water used in cleaning a DE filter shall be discharged to waste or other approved means.

10. (3) Precoat.

    1. (A) Precoating of the septa shall be in accordance with manufacturer’s recommendations to ensure adequate coating of DE prior to filtering water through the system.
    2. (B) A precoat pot may be installed on the suction side of the pump to ensure adequate coating of the filter septa.
    3. (C) No additional precoat equipment is needed on vacuum systems since the DE can be placed directly in the filter tank.
11. (4) Filter piping. The system piping shall be such that during precoat procedures the filtered effluent shall be refiltered or wasted without passing into the pool until the effluent is clear of suspended matter.

12. (5) DE substitutes. Synthetic substitutes such as cellulose products manufactured as DE replacements may be utilized.

    1. (d) Cartridge filters.

13. (1) General.

    1. (A) Cartridge type filters are permitted for use on Class E spas or Class F spas.
    2. (B) Approval of cartridge filters for use on all other classes of pools shall be on a case-by-case basis.

14. (2) Number.

    1. (A) One (1) extra complete set of cartridges per filter shall be kept on the premises at all times.
    2. (B) Replacement of cartridge elements shall be done whenever the requirements of 20 CAR § 136-105(b) cannot be maintained.
15. (3) Cleaning. Cartridge filters must be cleaned by soaking in an approved cleaning solution and/or by pressure spraying.
16. (4) Filter rate. Cartridge filters must filter at a rate not in excess of three hundred seventy-five thousandths gallons per minute per square foot (.375 gpm/sq. ft.).