How to Install a Water Softener

Hard water is more than an unpleasant nuisance; it can stain sinks, reduce the cleaning power of detergent, cause buildup in faucets and pipes, and shorten the life of a water heater. Though several types of salt-free water softeners are available, a salt-based (ion exchange) softener is still the most popular choice. (See the Water Softener Systems Buying Guide for more information on choosing a water softener.)

Though most homeowners choose to buy and maintain their own water softener, a viable option is to rent one. Over the long run, renting will cost more than buying, but it can save you the trouble of installing, maintaining, and repairing a system.

Installation Basics

Installing a water softener calls for basic plumbing skills. Unless you’re simply replacing an old water softener, you may need to cut into and connect new fittings and pipes. (If you have copper pipes, see Cutting & Joining Copper Pipe for how-to help.) If doing it yourself looks like too much trouble, consider hiring a local prescreened water softener installation pro.

Cabinet-type water softeners are installed as a single unit, which houses both a softening tank and a salt brine tank. Some water softeners have a separate salt brine tank that sits to the side of the softening tank.

If you don’t have an existing water softener, the first step down the path of installing one is to choose a location for the appliance. (See How to Choose a Water Softener Location.)

An important note: In households where sodium in the drinking water may cause a health risk, it is often recommended that only the hot water be softened or that certain drinking water faucets be bypassed by the softened water. If you intend to install your softener so that the cold water system is not served by it, place it after (downstream from) the water heater—but keep in mind that you will lose all of the benefits of water softening in your cold water system. Another option is to select a salt-free water softening system (see Salt-Free Water Softeners).

Plumbing a Water Softener

Most water softeners come with a bypass valve that you must assemble and attach to the unit. In addition, some local plumbing codes require that you install shutoff valves to the pipes that lead to and from this bypass valve so the water to and from the softener can be turned off easily. If your softener has such a bypass valve, attach it to the softener, following manufacturer’s instructions.

Position the water softener where it belongs so you can easily measure for the connecting pipes. Turn off the water at the water heater and shut off the house water supply valves. Then open a couple of bottom-floor faucets or hose bibbs to drain the water from the pipes. (For more about shutting off the water supply, see How to Shut Off the Water to Fixtures and Your House.)

Using a pipe cutter, cut into the water supply line and install elbow fittings so you can run two lines, to the inlet and the outlet ports of the bypass valve. Hard water from the water supply will run into the softener’s inlet, and soft water will run out to supply the house's fixtures and faucets. If you want an outlet, such as a hose bibb, to carry hard water, install a T fitting prior to the softener and run it to the outlet.

Cut and install the pipes that lead to the bypass valve. Solder all the fittings and nipples before attaching them to the plastic bypass valve (the heat from soldering could damage the plastic). If the pipes are too large, use a reducing fitting to install pipes of the correct size. Use the compression fittings supplied with the softener to attach the pipes to the unit.

Clamp the drain hose to the softener, and run it to a drain or utility sink. The end of the hose must be at least 2 inches above a drain hole and should be securely clamped. Connect the brine tank’s overflow tube, and follow the manufacturer’s instructions for any additional assembly.

Following the manufacturer’s instructions, set the bypass valve to the “bypass” position and turn on the water to run through the softener for a few minutes to flush out sediment and expel air in the pipes. Set the valve to the “service” position and plug the unit into a nearby receptacle. Fill the tank with water and salt as directed by the manufacturer.