SECTION 310:315-7-14. Recirculation system

(a)   General considerations.

(1)   A circulation system shall be provided which will include pumps, hair-catcher, and filters, together with all necessary piping connections to the inlets and outlets of the pool. The water heater, chlorinator, and suction cleaner are also usually connected with the recirculation system and shall be considered as integral parts thereof. The entire system and all component parts of swimming pools shall be designed to provide a minimum of three (3) replacements of the bathing water volume every twenty-four (24) hours (four (4) turnovers are recommended), with maximum frictional resistance. The required turnover rate at spas and other facilities appears in the appropriate section; note that at pools and spas with skimmers, the required skimmer flow, rather than turnover, may determine the minimum flow. Design is to be based on provisions for main drain flow at thirty (30) percent of the total recirculation, and thirty (30) gpm through each skimmer. This is represented as 0.3Q + 30n = Q = total recirculation flow rate and n = number of skimmers. (Main drain flow is 0.3Q.) These criteria, plus the maximum allowable filter flux (15 gpm/ft for rapid sand filters) and the maximum total dynamic head loss calculated assuming a "dirty" filter ready for backwash, comprise the basic design requirements for the most commonly designed pools and spas.

(2)   Filtration and disinfection are discussed in subsequent subchapters. A collector tank or other means for accommodating surge capacity shall be provided for all pools using overflow gutters connected to the recirculation system.

(b)   Pumps.

(1)   Centrifugal pumps are preferable for swimming pool circulation. Electric drive is also preferable. When pipe lines from suction cleaner lead to pump suction, a pump which will develop good vacuum must be used. The pump and piping at swimming pools shall be of such capacity as to provide for a turnover of pool water in at least eight (8) hours. Refer to the appropriate section for requirements at spas, water slides, and other facilities. When pressure filters are used, pumps must be designed to pass the required volume under the maximum head which may develop in the filters.

(2)   The pump shall have adequate capacity to provide the design recirculation flow rate at maximum calculated head loss, and 15 gpm/ft of sand filter area during backwash; the pump should be located below the water level of the pool when feasible, to avoid air-lock. Should it be necessary to locate the pump above the water level of the pool, a check valve shall be provided on the suction side of the pump unless a self-priming pump is furnished.

(3)   If the filter is located above the water level of the pool, then valves shall be provided in the inlet and discharge lines which can be closed when the filter is not in use.

(4)   A filtration pump equipped with a device that disables the pump operation shall be equipped with both an audible and visual alarm to alert the operator to the condition.

(c)   Strainers. The recirculation system shall include a strainer to prevent hair, lint, and other solids from reaching the pump and filters. Strainers shall be corrosion-resistant with openings not more than one-eighth (1/8) inch in size and shall be readily accessible for frequent cleaning. Larger openings for strainers will be considered only on a trial basis. At least two (2) baskets, or screens, must be provided. The area of strainer openings shall be at least four (4) times the cross-sectional area of the connecting pipe. A compound pressure gauge shall be installed to measure the pressure between the pump and the hair and lint strainer. Where filter systems are located above the pool water level, a standard vacuum gauge is acceptable.

(d)   Vacuum cleaner. Vacuum cleaner facilities, either portable or installed integrally in the pool piping system for the operation of a vacuum cleaner, shall be provided. Piping and hose shall be required to produce not more than fifteen (15) feet total head loss at the pump, while moving four (4) gallons per minute per linear inch of cleaner head. All pools shall be designed with pipes for vacuum cleaning facilities integrally with the pool piping or portable facilities will be provided. Vacuum cleaner heads with brushes are recommended. The mixture of water and sediment from a suction cleaner may, in the case of outdoor pools subjected to heavy dust loads, be discharged to an approved waste treatment system. The discharge from suction cleaners used in cleaning indoor pools, which are not subjected to heavy dust loads or in which sedimentation is slight, may be returned to the pool through the filter system. Any point source discharge must comply with the requirements of OAC 310:315-5-2 (relating to sewer).

(e)   Water heater. Indoor pools operated during the colder months shall be provided with some method of heating the pool water. Introduction of steam directly into the pool or the use of heating coils placed directly in the pool is prohibited. A heater designed to heat all or a part of the circulation water is preferable. Such a heater may be designed for use with steam or hot water and ample surface for heat interchange must be provided. Automatic thermal control is desirable. Provision should be made for easy removal of the heater parts for cleaning. A check valve shall be installed between the filter and the inlet side of the heater. On all heated pools, a fixed thermometer shall be placed on the recirculation line immediately downstream from the heater after blending and another on the return line from the pool. Thermometers shall be accessible and have a Fahrenheit scale.

(f)   Piping system. The determination of sizes of pipe, fittings, and valves on the complete main pump suction line from the swimming pool shall be based upon a rate of friction losses for piping of not more than six (6) feet per one hundred (100) feet of pipe based upon the Hazen-Williams formula for fifteen (15) year old piping. All piping on the discharge side of the pump for filtration and to the point for discharge of backwash water from the filter plant shall have pipe sizes determined on a basis of friction losses which shall be not more than twelve (12) feet per one hundred (100) feet and the velocity in any pipe shall not exceed ten (10) feet per second. Pipe selection shall be made based upon the Hazen-Williams formula for fifteen (15) year old pipe. In the determination of pipe sizes required, the criterion which would call for the largest pipe size shall govern. All pool piping shall be supported by piers or other substantial means to preclude possible settlement which will either provide dirt traps or air pockets and a condition which might result in rupture of the lines. The use of plastic pipe on suction lines and lines beneath the pool and bathhouse structure is not recommended. All plastic pipe used shall bear the approval seal of the National Sanitation Foundation. All piping shall be labeled or color coded and all valves shall be labeled.

(g)   Rate-of-flow indicator. Every public swimming pool distribution system including those for wading pools shall be provided with an accurate and durable rate-of-flow indicator, installed in accordance with the manufacturer's recommendations and with the required uniform distance upstream and downstream for accurate response. In pressure sand filter installations, a rate indicator shall be provided and located on the filter inlet line so as to record both filtration and backwashing rates. It shall be calibrated for and provided with an easily readable scale reading in gallons per minute, and shall have a range at least ten (10) percent below the required filtration rate and ten (10) percent above the required backwash rate. It shall be accurate within ten (10) percent of true flow. In a diatomite type filter installation, a rate-of-flow indicator can be located wherever convenient to visibly indicate the flow rate, preferably in the filter effluent line.

(h)   Outlets. All pools must be provided with an outlet at the deepest point to permit the pool to be completely and easily drained. Each public bathing place subject to licensure by the Department permitted after September 1, 2009 that does not utilize indirect suction shall be provided with an unblockable suction outlet as defined in American National Standards Institute (ANSI) A112.19.8-2007, or have multiple outlets, placed a minimum of 3 feet apart measured from center point of the drain cover/grate. Outlet openings of the grating in the floor of the pool shall be at least four (4) times the area of the discharge pipe. Each submerged suction outlet shall be fitted with a cover/grate that conforms to the entrapment protection standards of the ANSI A112.19.8-2007 performance standard. Submerged suction outlet cover/grate shall be installed according to the manufacturer's installation instructions. Field fabricated sumps shall be constructed according to ANSI A112.19.8-2007. Openings in the drain cover(s) shall be designed for a maximum velocity of one and one-half (1-1/2) feet per second. The outlet shall be marked by a dark colored stripe outlining the main drain, disk, or circle unless the plate or grating is of a contrasting color. Multiple outlets to meet this requirement shall be provided where the width of the pool is more than thirty (30) feet. In such cases, outlets shall be spaced not more than twenty (20) feet apart and not more than fifteen (15) feet from the side walls. A line shall run from the main drain(s) to a manifold connected to the inlet of the hair and lint strainer. A separate line shall run from each skimmer to the manifold. A valve that will permit adjustment of flow shall be installed in each line carrying water from the pool. Where provided, the vacuum line shall connect to the manifold through a suitable valve. Vacuum lines shall have a cover in place when not in use. After September 1, 2009 any existing pool licensed by the Department that plans modifications relative to the replacement or modification of submerged suction outlet cover/grates, or the addition of systems or devices intended to minimize the risk of physical or suction entrapment, shall submit a scope of work as specified under OAC 310:315-3-1 (relating to plans and specifications). At a minimum the proposal shall include the make and model of all equipment to be installed. Documentation shall be provided that all cover/grates conform to the entrapment protection standards of the American Society of Mechanical Engineers/American National Standards Institute (ASME/ANSI) A112.19.8-2007. Additionally the modification shall incorporate at least one of the following devices or systems relative to prevention of suction entrapment:

(1)   A safety vacuum release system which ceases operation of the pump, reverses the circulation flow, or otherwise provides a vacuum release at a suction outlet when a blockage is detected, that has been tested by an independent third party and found to conform to American Society of Mechanical Engineers/American National Standards Institute (ASME/ANSI) A112.19.17 or American Society for Testing Materials (ASTM) standard F2387;

(2)   A suction-limiting vent system with a tamper-resistant atmospheric opening;

(3)   A gravity drainage system that utilizes a collector tank;

(4)   An automatic pump shut-off system;

(5)   A device or system that disables the drain; or

(6)   An unblockable suction outlet as defined in American National Standards Institute (ANSI) A112.19.8-2007, multiple outlets placed a minimum of 3 feet apart measured from center point of the drain cover/grate, or any other system determined by the department to be equally effective as, or better than, the systems described in (1) through (5), at preventing or eliminating the risk of injury or death associated with pool drainage systems.

(i)   Inlets. Multiple inlets shall be provided and shall be so spaced that each inlet will serve a linear distance of not more than fifteen (15) feet, provided that the distance from side wall or corner to adjacent inlet in an end wall shall not exceed five (5) feet. At least four (4) inlets are required at pools of any size, and more may be required at recessed features (stairs, seats, etc.) or in pools with irregular shapes, to achieve satisfactory disinfectant distribution. On pools less than sixteen hundred (1600) square feet in area, only directional (eye-ball type) inlets are permitted. In pools with surface area greater than sixteen hundred (1600) square feet or length in excess of sixty (60) feet, inlets shall be placed at fifteen (15) feet intervals around the entire perimeter. In any case, an adequate number of inlets shall be provided, properly spaced, and located to accomplish complete and uniform recirculation and maintenance of uniform disinfectant residual at all times. Inlets shall be a minimum of eighteen (18) inches below the water surface. Each inlet shall be designed as an orifice subject to adjustment or at least must be provided with an individual gate valve to permit adjustment of water volume and/or velocity to obtain a balanced circulation. In the event recessed stairs are used, an inlet at the stairs must be provided to assure adequate circulation.

(j)   Overflow gutters. Overflow gutters shall be required on all pools having a surface area or more than twenty-four hundred (2400) square feet. Pools having a surface area of twenty-four hundred (2400) square feet or less shall be provided either with overflow gutters or skimmers. Overflow gutters shall extend completely around the pool except at steps or recessed ladders, and shall be designed to assure that water does not wash back into the pool from the gutter. Guttered pools shall be designed for at least some water to be overflowing into the gutters or into surge weirs at all times, not just when the pool is at full bather capacity, for continuous removal of surface oils and debris. The gutter, drains, and piping shall be designed to rapidly remove overflow water caused by recirculation displacement, wave action, or other causes produced from the maximum pool bathing load. The opening into the gutter beneath the coping shall be not less than four (4) inches, and the interior of the gutter shall be not less than four (4) inches wide with a depth of at least three (3) inches. Where large gutters are used, they shall be designed to prevent entrance or entrapment of bathers' arms or legs. The overflow edge shall be rounded and shall not be thicker than two and one-half (2-1/2) inches for the top two (2) inches. Prefabricated gutter and return systems will be evaluated on a case-by-case basis.

(k)   Gutter outlets. Drainage outlets shall be provided at least every fifteen (15) feet and the gutter bottom may be level, or preferably pitched slightly, to these outlets. Outlet pipes shall have a minimum inside diameter of two (2) inches. Outlets shall be covered by gratings. Angle gutter drains, which are not as subject to stoppage, are recommended. Drainage from overflow gutters may be discharged to sewers (without direct connection), or connected to the recirculation system through a properly designed surge tank or other acceptably designed provision for handling surge capacity, such as deep gutter channels. The gutter, drains, and return piping to the surge tank shall be designed to rapidly remove overflowing water caused by recirculation displacement, wave action, or other causes produced from the maximum pool bathing load. The outlet fittings shall have a clear opening in the grating at least equal to one and one-half (1-1/2) times the cross-sectional area of the outlet pipe. Open, roll-over, semi-recessed, or overflow gutters recessed in the side wall of the pool may be used, provided the design is such as to minimize accidents and to enable the gutter to be easily cleaned.

(l)   Skimmers. Skimming devices are permitted in lieu of gutters on swimming pools with not more than twenty-four hundred (2400) square feet of surface area, providing approved handholds are installed and sufficient motion to the pool water is induced by the pressure return inlets. At least one (1) skimming device shall be provided for each six hundred (600) square feet or fraction thereof. The required surface skimmers shall be located at least thirty (30) feet apart, measured horizontally. One (1) skimmer shall be located on the leeward side. Where used, skimming devices shall be built into the pool wall, shall develop sufficient velocity on the pool water surface to induce floating oils and wastes into the skimmers from the entire pool area, and shall meet the following general specifications:

(1)   The piping and other pertinent components of the skimmers shall be designed for a total capacity of at least fifty (50) percent of the required filter flow of the recirculation system, and no skimmer shall be designed for a flow-through rate of less than thirty (30) gallons per minute.

(2)   The skimmer weir shall be automatically adjustable and shall operate freely with continuous reaction action to variations in water level over a range of at least four (4) inches. The weir shall operate at all flow variations as described in the above paragraphs. The weir shall be of such buoyancy and design as to develop an effective velocity.

(3)   An easily removable and cleanable basket or screen through which all overflow water must pass shall be provided to trap large solids.

(4)   The skimmer shall be provided with a device to prevent air-lock in the suction line. If an equalizer pipe is used, it shall provide an adequate amount of water for pump suction should be water of the pool drop below the weir level. If any other device or arrangement is used, a sufficient amount of water for pump suction shall be assured. When the equalizer pipe is used, it shall be sized to meet the capacity requirements of the filter and pump and shall in no case be less than two (2) inches in diameter. This pipe shall be located at least one (1) foot below the lowest overflow level of the skimmer. It shall be provided with a valve or equivalent device that will remain tightly shut under normal operating conditions but will automatically open when the skimmer becomes starved. Equilizer openings shall comply with the drain cover provisions of OAC 310:315-7-14(h) (related to outlets).

(5)   The skimmer shall be of sturdy corrosion-resistant materials.

(6)   Where multiple skimmers are installed, valves shall be provided to isolate each skimmer and/or regulate the flow through each skimmer. See OAC 310:315-7-14 (relating to recirculation systems) for additional details.

(7)   In addition to the above requirements, the skimmers must be approved and listed as currently approved by the National Sanitation Foundation (NSF) Standard 50 - Circulation System Components and Related Materials for Swimming Pools, Spas/Hot Tubs.

[Source: Amended at 26 Ok Reg 2003, eff 6-25-09]