How to Install a Whole-House Water Filter

A whole-house filter is installed in the main water line and filters all of the water coming into a house.


Drain the System

First, turn off the water supply at the main water supply shutoff. Next, from the lowest point in the home, open a faucet to release pressure and drain most of the water from the system.


Cut the Pipe


Once you’ve selected the location for your filter, use the template provided with the kit to mark the pipe for exact placement. Remember that you’ll need to change the cartridge periodically, and select a location with enough clearance beneath the filter tank to allow easy removal and reattachment.

Use a pipe cutter to make two cuts, and remove the marked section of pipe. Use the twist handle to tighten the cutter onto the pipe so the blade lines up with your mark, then rotate the cutter around the pipe as you continue twisting the handle. Keep rotating the cutter around the pipe until it cuts all the way through. This may take a minute or so. (Have a bucket handy to catch any excess water when the pipe is cut — especially if you’re standing directly underneath.) Once you’ve cut out the section, use the reamer blade on the cutter to remove any burrs from inside the freshly cut pipe.


Pro Tip

If you’re installing the filter in a tight space, use a mini-cutter. It works the same way as an ordinary pipe cutter but has a smaller body and handle for easier use in narrow spaces.


Attach the Fittings

Place a compression nut, small end first, on one of the cut pipe ends. Slide on the ferrule (Image 1). Repeat the same steps on the other side.

Thread a brass fitting onto the “in” and the “out” ports of the filter housing. Install them according to the manufacturer’s recommendations. (In this example, the red seal inserts into the port.) (Image 2) Use Teflon tape to ensure a good seal between the fitting and the filter port. Tighten the fittings onto the filter until they’re snug, but don’t over-tighten.


Position the Filter

Important: Install the filter so the flow of water enters the “in” port and exits through the “out” port. The filter won’t function properly if installed backward. (The “in” port should be on the end closer to the water meter; the “out” should point toward the water heater.)

Position the filter on the water line, and let it hang temporarily between the two ferrules (Image 1).

Hand tighten the compression nuts onto the fitting bodies. Keeping the filter straight and upright, tighten the fittings, using two wrenches (Image 2).


Turn On the Water

The filter kit comes with a special handle used to turn the inlet valve on top to various positions — “off,” “bypass” and “filter.” With the filter properly installed, turn the valve to the “off” position. Slowly turn the water back on at the main shutoff valve, and check the filter for leaks.

Use the handle to turn the valve from “off” to the “filter” position. The tank should fill with water and the unit will begin filtering. Check again for leaks. If you detect leaks at the compression fittings or the filter housing, tighten until the dripping stops.

Important: Though it’s uncommon in newer homes, some houses use the water pipes as a ground for the electrical system. If this is the case in your home, you must install a jumper wire at the filter (provided with most kits) so the electrical ground is not interrupted by the placement of the filter.


Change the Filter as Needed

You’ll need to change the cartridge at intervals recommended by the manufacturer. In the case of the whole-house filter, the handle used to turn the inlet valve doubles as a tool to remove the filter tank when it’s time to change filters.

Turn the valve handle to the “off” position.

Use the handle to loosen and remove the tank from the housing. Have a bucket handy to catch any water.

Pour the water from the tank and discard the old cartridge. Wipe the inside of the tank with a clean cloth.

Insert a new cartridge and reattach the tank to the housing. Return the valve to the “filter” position.

Open one of the faucets slowly, and allow the water to run for a few seconds to allow trapped air to escape.

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