A standard water filter housing is made up of three parts: the filter cap, filter sump, and filter cartridge. The sump is a plastic container that’s made to hold the cartridge in place and channel water through it as required. The filter cap allows water to flow into and out of the sump correctly. Inside the sump, you can put any filter cartridge that fits, including sediment or carbon filters. Some filter housings are sold with cartridges included, but it’s easy to find those that allow you to choose your own filter type.
Inside the sump, you’ll find a small tab and sealing ring to hold the bottom of the cartridge filter in place and seal it. A similar tab can be found on the underside of the filter cap to hold the top of the cartridge in place. Around the top of the sump, where it connects to the filter cap, you’ll find a rubber O-ring that helps seal the two pieces together and eliminate leaks.
Water filter housing sumps come in several colors, including white, blue, red, and clear, with the color often indicating what they are used for. A red sump and cap, for example, may indicate that the filter is designed for hot water filtration. Filter caps are typically black or white.