D.C. Mun. Regs. tit. 25, r. 25-C408
The pool recirculation system shall be operated at all times when the pool is open for use. The recirculation system may be shut off three (3) hours after the pool closes and shall be turned back on three (3) hours before opening the pool. Shut down time shall be controlled by a time clock.
Recirculation and treatment equipment such as filters, recessed automatic surface skimmers, water ionizers, ozone generators, disinfection feeders and chlorine generators shall be tested and approved using the NSF/ANSI Standard 50-2007, Circulation System Components and Related Materials for Swimming Pool and Spas/Hot Tubs.
The recirculation system shall be designed to provide a minimum of four (4) turnovers of the pool volume per day. Pools that are less than one thousand square feet (1000 sq. ft.) shall be required to provide eight (8) turnovers per day.
The design pattern of recirculation flow shall be one hundred percent (100%) through the main drain piping and one hundred percent (100%) through the perimeter overflow or sixty percent (60%) through the skimmer system.
All swimming pools including wading pools and spa pools that are open to the public and that are built without a main drain collector tank shall be retrofitted with a properly sized and piped collector tank to eliminate direct suction through the main drain.
All existing public swimming pools with direct suction shall install a main drain cover that meets the ANSI/ASME A112.19.8-2007 standard for drain covers.
Public pools and spas with a single main drain (other than an unblockable drain) shall be equipped with a device or system such as a safety vacuum release system to prevent entrapment.
Public pools and spas that are not in operation do not need to meet the requirements specified in sections 408.5 and 408.6 until they resume operations.
A construction permit shall be obtained from the Department of Consumer and Regulatory Affairs prior to installation of a collector tank.
Any pool that cannot be retrofitted as required in Subsections 408.5 and 408.6 shall be closed.
Newly constructed swimming pools and spas built after the effective date of these regulations shall be built with either:
Hot water facilities shall be disinfected with automatic chemical feed equipment as specified in Subsection 607.3 of these regulations.
The turnover rate shall not exceed thirty (30) minutes.
The whirlpool shall be designed and the hydraulic analysis calculated to provide a thirty (30)- minute turnover rate when the filter is at maximum pressure and ready to be cleaned or backwashed.
The filter shall be cleaned or backwashed when the filter pressure and the flow meter indicate it is necessary.
The plumbing system shall be designed to preclude entrapment in main drains.
Return fitting(s) shall be provided and arranged to facilitate a uniform circulation of water and maintain a uniform sanitizer residual throughout the entire spa or exercise spa.
Suction fittings shall be sized and installed in accordance with the manufacturer's specifications. Spas and exercise spas shall not be used or operated if the suction outlet cover is missing, damaged, broken or loose.
Submerged vacuum fittings shall be prohibited.
D.C. Mun. Regs. tit. 25, r. 25-C408