ATCP 76.11(6)(a)2.2. Filter shells and appurtenances shall be maintained in operating condition. Pf ATCP 76.11(6)(a)3.3. The backwash procedure shall follow the filter manufacturer’s written directions. ATCP 76.11(6)(a)4.4. Backwash procedures shall be conspicuously posted in the filter area on an easily read chart. ATCP 76.11(6)(a)5.5. Filter media shall be inspected annually and cleaned or replaced when necessary. ATCP 76.11(6)(b)(b) Sand filters. The following types of sand filters shall be backwashed as recommended by the manufacturer: ATCP 76.11(6)(c)(c) Diatomaceous earth filters. Diatomaceous earth filters shall meet all of the following: ATCP 76.11(6)(c)1.1. Pressure and vacuum type diatomaceous earth filters shall be backwashed as recommended by the manufacturer. Pf ATCP 76.11(6)(c)2.2. Septum covers shall be removed, cleaned, or replaced when they no longer provide effective filtration or create a friction loss preventing maintenance of the required recirculation rate. Pf ATCP 76.11(6)(c)3.3. Diatomaceous earth wastewater separation tanks, where installed, shall be cleaned according to manufacturer instructions.Pf ATCP 76.11(6)(c)4.4. Positive displacement feeder suction intake shall meet all of the following: ATCP 76.11(6)(c)4.d.d. Installed and maintained to prevent backflow of water into the tanks and to prevent the slurry from being siphoned out of the tanks into the pool recirculation system. P ATCP 76.11(6)(c)5.a.a. The lowest effective concentration of solution shall be used in a diatomaceous earth slurry feeder. ATCP 76.11(6)(c)5.c.c. The diatomite slurry feeder head and lines shall be flushed as recommended by the manufacturer to assure proper and continuous operation. Pf ATCP 76.11(6)(c)5.e.e. If connection is to a potable water supply line, the supply line shall be equipped with an approved backflow or backsiphonage prevention device. P ATCP 76.11(6)(d)(d) Cartridge filters. Cartridge filters shall meet all of the following: