3129B Rapid Sand Pressure Filters — 2025 California Building Code
California Building Code (Title 24, Part 2) · 2025 edition · updated 2026-10-19 · California
CBSC: official editions, supplements and errata
Italicized text is a California amendment to the model code, as printed in the official publication.
Cite as: 2025 California Building Code (Title 24, Part 2) § 3129B · Effective January 1, 2026 · Official source: Building Standards Commission
In addition to the requirements for all filters as indicated in Section 3128B, the following apply to rapid sand pressure filters.
3129B.1 Flow rates.¶
The filtration rate shall not exceed 3 gallons per minute per square foot (122.24 L/m per m [2] ) of filter area. The back- wash rate shall not be less than 15 gallons per minute per square foot (611.2 L/m per m [2] ) of filter area.
3129B.2 Filter media.¶
The filter shall contain not less than a 20-inch (508 mm) depth of media and not less than a 10-inch (254 mm) depth of filter gravel above the underdrain system.
3129B.2.1 The filter media shall have an effective particle size between 0.40 and 0.55 millimeters and a uniformity coefficient not exceeding 1.75.
3129B.2.2 The filter gravel shall be sized and placed to provide uniform flow distribution from the underdrain system and to support the bed of filter sand without loss of sand to the pool or without development of jet streams or channeling in the filtration media.
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