Gauges and Release Valves. An owner shall ensure that the circulation system for a recreational pool, semipublic pool, or public spa includes the following: A pressure gauge on the filter or on the influent side of the filter piping; A pressure gauge on the effluent side of the filter piping; A vacuum or compound gauge on the influent side of a pump; A flow meter that: Indicates the rate of flow through the circulation system; Has a permanent scale readable in gallons per minute; Is accurate to within 10 percent of the actual flow; and Reads in the range encompassing the minimum and maximum flow rate; A thermometer on the return line to a pool or spa if the circulation system includes a heating system; and A manually operated air release valve on a pressure filter or a separation tank, or both. Turnover Rate. An owner shall ensure that: A recreational pool, semipublic pool, or public spa is constructed to produce the following minimum turnover rates, with continuous 24-hour flow: Pools for swimming and diving: Minimum turnover rate = volume of pool in gallons/480 minutes; Pools for water recreational attractions and therapy: Minimum turnover rate = volume of pool in gallons/360 minutes; Pools for wading have a minimum turnover rate equal to the greater of: Volume of pool in gallons/120 minutes; or The minimum flow required for the skimmer system and main drain to operate according to the manufacturer's specifications; and Spas: Minimum turnover rate = volume of spa/30 minutes; The flow through a circulation system is maintained between the minimum turnover rate and the design capacity of the filter system and associated piping; and A limited public-use pool has a turnover rate in conformance with: American National Standard for Residential Inground Swimming Pools; or American National Standard for Aboveground/Onground Residential Swimming Pools. Head Loss Calculations. An owner of a recreational pool, semipublic pool, or public spa shall ensure that head loss calculations include the following: Piping head loss, found by using: The Hazen-Williams formula which is: piping head loss per 100 feet of pipe = 0.2083 (100 / C) 1.852 (Q1.852/ D4.865) Standard engineering tables; Equipment head loss, including filters, valves, heaters, and other circulation equipment, based on the manufacturers' specifications for the equipment at the design flow rate, and filter pressure differential with the filter in a clean and in a dirty condition; Elevation of pump suction and discharge in relation to the pool or spa water surface level; and Determination of the total dynamic head of the circulation system for use in pump selection. Surface to Bottom Flow Ratio. An owner of a recreational pool, semipublic pool, or public spa shall ensure that: Piping for surface outlets is designed to accommodate 80 percent of the flow; and Piping for bottom outlets is designed to accommodate 20 percent of the flow. An owner of a recreational pool or semipublic pool may have a gutter surface overflow system with a flow design of 50 percent from the surface outlets and 50 percent from the bottom outlets. Filter Capacity. An owner of a recreational pool, semipublic pool, or public spa shall ensure that a filter: Operates within the filter design flow rate; Has a filtration capacity sufficient to operate in the range between the minimum turnover rate and the filter design flow rate when the circulation system is at the: Lowest level of calculated total dynamic head when the filter is in a clean condition; and Highest level of calculated total dynamic head when the filter pressure differential is at the maximum allowed in Regulation .43E of this chapter. Interconnections Between Pools. An owner of a recreational pool, semipublic pool, or public spa shall ensure that a pool is not interconnected with a: Spa or wading pool except during the filling of a spa or wading pool; and Spray pool. For a public pool or spa with a flow rate that is at least 10 percent greater than the design capacity of the filter system or associated piping or at least 10 percent less than the minimum turnover rate as specified in §B of this regulation, an owner or operator shall: Record the information required in Regulation .46C of this chapter in 1-hour intervals; and Prior to restoring normal circulation, vacate the pool or spa of all bathers until: 15 minutes after restarting the pump; and The water quality is verified as not exceeding the limits set for a major violation under Regulation .05(7-1) of this chapter.