Filbur FC 3430 Spa Pool Replacement Filter Cartridge airreliefvalves Air bleed assemblies help release Air bleed assemblies help release trapped air from filter systems so pressure can stabilize and filtration can operate more efficiently Heaters in a no box format are useful when the surrounding system layout does not require the added enclosure and the replacement needs to match that simpler configuration A properly selected cartridge helps restore intended filtration performance and contributes to cleaner routine maintenance this replacement filter cartridge helps restore dependable debris capture and contributes to cleaner overall water care results