Filtering at the point where water enters the house is the efficient way to do it. One cartridge on the main line means every tap, every shower and every appliance draws from the same filtered supply, which also helps protect water heaters, dishwashers and plumbing from the sediment that shortens their lives. This Pentair OMNIFilter whole home system is built on the 20-inch heavy duty Big Blue format, sized for households with higher water demand and connecting to a 1-inch line. Two features make the maintenance painless. A quarter-turn bypass diverts water around the housing, so you can change a cartridge without shutting off the water to the house, which matters when the rest of the household is not on your schedule. A pressure relief button vents the pressure trapped inside the housing before you unscrew it, and the valve-in-head design keeps the head plumbed in place while the sump comes away in your hands. The filter itself is sold separately, which is deliberate: it lets you match the cartridge to your own water, whether that means sediment reduction, taste and odor reduction, or lead and cyst reduction. The system is for cold water use only. Replace the cartridge when you notice a drop in water pressure or a change in water quality.