North Carolina Administrative Code › Title 15A - Environmental Quality › Chapter 18 - ENVIRONMENTAL HEALTH › Subchapter A - SANITATION › Section .2500 - PUBLIC SWIMMING POOLS › Section 18A .2519 - FILTERS

Current through Register Vol. 39, No. 2, July 15, 2024
(a) All swimming
				  pools shall be equipped with a filtration system for the purpose of clarifying
				  the swimming pool water; said filtration system shall be an integral part of
				  the circulation system and shall consist of one or more units of sand type
				  filters, of diatomacious earth type filters, or of cartridge type
				  filters.
(b) All filter units shall
				  be designed and constructed in accordance with Section 5 of the National
				  Sanitation Foundation's Standard number 50 which is hereby adopted by reference
				  in accordance with
				  G.S.
				  150B-14(c), or
				  equivalent.
(c) When a sand type
				  filter is installed on a swimming pool, it may be either a gravity or a
				  pressure sand type filter, and it may be either a standard-rate sand type
				  filter which shall be designed for filtration rates not in excess of three
				  gallons per minute per square foot (122 L per minute per square meter) of sand
				  bed area, or a high-rate sand type filter which shall be designed for
				  filtration rates not in excess of 15 gallons per minute per square foot (612 L
				  per minute per square meter) of sand bed area or the flow rate indicated for
				  commercial pools in the most recent NSF listing.
(d) When a sand type filter is installed on a
				  swimming pool, it shall be designed and installed such that it may be
				  backwashed at a rate recommended by the manufacturer or, in the absence of
				  manufacturer's recommendations, at a rate not less than 15 gallons per minute
				  per square foot (612 L per minute per square meter) of filter bed area. The
				  backwash water shall be discharged to waste. A sight glass or other means for
				  viewing the clarity of the backwash water shall be provided.
(e) If the sand type filter is designed to be
				  operated in conjunction with a coagulant, a chemical feeder shall be provided
				  for adding the coagulant ahead of the filters.
(f) When a diatomacious earth type filter is
				  installed on a swimming pool, it may be either a pressure or vacuum type and it
				  may be designed to operate either with or without continuous body feed.
				  Diatomaceous earth filters which operate with continuous body feed shall be
				  designed for filtration rates not in excess of 2.5 gallons per minute per
				  square foot (102 L per minute per square meter) of filter area; and
				  diatomaceous earth filters which operate without continuous body feed shall be
				  designed for filtration rates not in excess of two gallons per minute per
				  square foot (82 L per minute per square meter) of filter area.
(g) When a diatomaceous earth type filter is
				  installed on a swimming pool, it shall be designed and installed with
				  provisions for cleaning by one or more of the following methods:
(1) backwashing at two gallons per minute per
				  square foot minimum;
(2)
				  air-bump-assist backwashing;
(3)
				  spray wash, (either mechanical or manual); or
(4) agitation.