R392-302-20. Filtration

  (1) The filter system must provide for isolation of individual filters for backwashing or other service.

  (2) The filtration system must be designed to allow the pool operator to easily observe the discharge backwash water from the filter in order to determine if the filter cells are clean.

  (3) A public pool must use either a rapid sand filter, hi-rate sand filter, precoat media filter, a cartridge filter or other filter types deemed equivalent by the Department. All filters must comply with the standard NSF/ANSI 50-2015.

  (4) Gravity and pressure rapid sand filter requirements.

  (a) Rapid sand filters must be designed for a filter rate of 3 gallons, 11.36 liters, or less, per minute per square foot, 929 square centimeters, of bed area at time of maximum head loss. The filter bed surface area must be sufficient to meet the design rate of flow required by Section R392-302-16, Table 1, for required turnover.

  (b) The filter system must be provided with influent pressure, vacuum, or compound gauges to indicate the condition of the filters. Air-relief valves must be provided at or near the high point of the filter or piping system.

  (c) The filter system must be designed with necessary valves and piping to permit:

  (i) filtering of all pool water;

  (ii) individual backwashing of filters to a sanitary sewer at a minimum rate of 15 gallons, 56.78 liters, per minute per square foot, 929 square centimeters, of filter area;

  (iii) isolation of individual filters;

  (iv) complete drainage of all parts of the system;

  (v) necessary maintenance, operation and inspection in a convenient manner.

  (d) Each pressure type filter tank must be provided with an access opening of at least a standard size 11 inch, 27.94 centimeters, by 15 inch, 38.10 centimeters, manhole with a cover.

  (5) Hi-rate sand filter requirements.

  (a) Hi-rate sand filters must be designed for a filter rate of less than 18 gallons, 68.14 liters, per minute per square foot, 929 square centimeters, of bed area. The filter bed area must be sufficient to meet the design rate of flow required by Section R392-302-16, Table 1, for required turnover. Minimum flow rates must be at least 13 gallons, 49.21 liters, per minute per square foot, 929 square centimeters, of bed area. The minimum flow rate requirement may be reduced to a rate of no less than 10 gallons per minute per square foot of bed area where a multiple filter system is provided, and where the system includes a valve or other means after the filters which is designed to regulate the backwash flow rate and to assure that adequate backwash flow can be achieved through each filter per the filter manufacturer's requirements.

  (b) The filter tank and all components must be installed in compliance with the manufacturer's recommendations.

  (c) An air-relief valve must be provided at or near the high point of the filter.

  (d) The filter system must be provided with an influent pressure gauge to indicate the condition of the filter.

  (6) Vacuum or pressure type precoat media filter requirements.

  (a) The filtering area must be compatible with the design pump capacity as required by R392-302-16(7). The design rate of filtration may not exceed 2.0 gallons per minute per square foot, 7.57 liters per 929 square centimeters, of effective filtering surface without continuous body feed, nor greater than 2.5 gallons per minute per square foot, 9.46 liters per 929 square centimeters, with continuous body feed.

  (b) Where body feed is provided, the feeder device must be accurate to within 10 percent, must be capable of continual feeding within a calibrated range, and must be adjustable from two to six parts per million. The device must feed at the design capacity of the circulation pump.

  (c) Where fabric is used, filtering area must be determined on the basis of effective filtering surfaces.

  (d) The filter and all component parts must be designed and constructed of materials which will withstand normal continuous use without significant deformation, deterioration, corrosion or wear which could adversely affect filter operations.

  (e) If a precoat media filter is supplied with a potable water supply, then the water must be delivered through an air gap.

  (f) The filter plant must be provided with influent pressure, vacuum, or compound gauges to indicate the condition of the filter. In vacuum-type filter installations where the circulating pump is rated at two horsepower or higher, an adjustable high vacuum automatic shut-off device must be provided to prevent damage to the pump. Air-relief valves must be provided at or near the high point of the filter system.

  (g) A filter must be designed to facilitate cleaning by one or more of the following methods: backwashing, air-bump-assist backwashing, automatic or manual water spray, or agitation.

  (h) The filter system must provide for complete and rapid draining of the filter.

  (i) Diatomaceous earth filter backwash water must discharge to the sanitary sewer system through a separation tank. The separation tank must have a sign that meets the requirements of a "2 Inch Safety Sign" in R392-302-39(1), (2) and (3)(b) warning the user not to start up the filter pump without first opening the air relief valve.

  (j) Personal protection equipment suitable for preventing inhalation of diatomaceous earth or other filter aids must be provided.

  (7) The Department may waive NSF/ANSI 50-2015 standards for precoat media filters and approve site-built or custom-built vacuum precoat media filters, if the precoat media filter elements are easily accessible for cleaning by hand hosing after each filtering cycle. Site-built or custom-built vacuum precoat media filters must comply with all design requirements as specified in Subsection R392-302-20(6). Any design which provides the equivalent washing effectiveness as determined by the Department may be acceptable. Where the Department or the local health department determines that a potential cross-connection exits, a hose bib in the vicinity of the filter to facilitate the washing operation must be equipped with a vacuum breaker listed by the International Association of Plumbing and Mechanical Officials, IAPMO, the American Society of Sanitary Engineering, A.S.S.E., or other nationally recognized standard.

  (8) Vacuum or pressure type cartridge filter requirements.

  (a) Sufficient filter area must be provided to meet the design pump capacity as required by Subsection R392-302-16, Table 1.

  (b) The designed rate of filtration may not exceed 0.375 gallons, 1.42 liters, per minute per square foot, 929 square centimeters, of effective filter area.

  (c) The filter and all component parts must be designed and constructed of materials which will withstand normal continuous use without significant deformation, deterioration, corrosion or wear which could adversely affect filter operations. The filter element must be constructed of polyester fiber only.

  (d) The filter must be fitted with influent and effluent pressure gauges, vacuum, or compound gauges to indicate the condition of the filter. In vacuum type filter installations where the circulating pump is rated at two horsepower or higher, an adjustable high vacuum automatic shut-off must be provided to prevent damage to the pump. Air-relief valves must be provided at or near the high point of the filter system.

  (e) Cleaning of cartridge type filters must be accomplished in accordance with the manufacturer's recommendations.