When you’re looking for a whole house water filter (meaning all your water is filtered right from the main line -- faucets, showers, toilets, laundry, etc.), there are four main variables to keep in mind:
Flow rate is basically just what it sounds like -- the amount of water available at any one time (measured in gallons per minute or GPM) for your sinks, water heater, shower, etc. Most appliances and your toilet should have their demand rate printed on them: For example, a showerhead usually requires 2.5 to 5 GPM, and a toilet 5. Calculate the flow rate you’ll need by considering all the water outlets in your house, how often they’re used at the same time, and the size of your family. Typically, it’ll be somewhere between 15 and 40 GPM. Anything less than 10 is definitely not enough.
A larger filter means more water flow and greater pressure, and also a longer service interval. Most houses require a 4.5-inch by 20-inch filter, though larger homes might need something bigger.
A good quality filter will last for 100,000 to 150,000 gallons in a normal home, though rougher water sediment may shorten this estimate.
Go for a 1-inch port system. Even if the rest of your home uses piping that’s ¾-inch, the 1-inch system will still work just fine and keep more than enough water flowing through your house.
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