How to Install a Water Softener

Where should a water softener be installed?

Install the softener on the main supply line after the water meter or well pressure tank and before the water heater. EPA WaterSense adds that, where possible, it should sit after the branch to outdoor hose bibs or irrigation, so you are not softening lawn water. Penn State notes toilets, outside spigots and basement sinks can also be bypassed.

On a well, SoftPro's Elite install guide says the softener will not work properly ahead of the pressure tank. Sediment filters, iron filters and neutralizers go upstream of the softener, per the Pentair 5600SXT manual; SoftPro's guide puts a UV unit after it. Check our sizing guide before you order.

Pick a level floor within reach of a drain and an outlet. Pentair asks for ambient temperatures between 34°F and 120°F, and QWT's guide says freezing voids the warranty and that water above 120°F damages softeners.

Install numbers from the manuals

• 20–125 psiworking water pressure rangePentair 5600SXT manual
• 10 ftminimum pipe run from softener to water heaterPentair 5600SXT manual
• 1/2 inminimum drain line diameter (3/4 in over 20 ft)Pentair 5600SXT manual
• 1 inminimum air gap, or 2 pipe diameters if largerPentair 5600SXT manual
• 50 galwater used per regenerationPenn State Extension

What do you need before you install a water softener?

You need the maker's manual, fittings for your pipe type, drain tubing and a grounded outlet. Pentair says the outlet must be grounded and always on, so avoid a switched outlet, and SoftPro's code checklist (SoftPro, a store run by our team) asks for one within 10 feet with no extension cord.

QWT's parts list for a Fleck 5600SXT covers thread seal tape, 1/2-inch ID drain tubing with a hose clamp, drain fittings and push-fit connectors for copper, PEX or CPVC. Pentair adds three rules: use plumber's tape on threads, use only silicone grease on O-rings, and never use pipe smaller than your main line. Where galvanized pipe meets new copper, use dielectric connectors.

Check permits first. SoftPro's guide puts permits at $50 to $300, and our cost guide covers what a plumber charges if you would rather not do it yourself.

How to install a water softener, step by step

Read your manual end to end before cutting anything; drain ports, brine fittings and menus differ by brand.

1. Turn off the water heater. Set gas units to pilot or switch off power to electric units.
2. Shut off the main and drain the lines. Open a low and a high faucet to relieve pressure.
3. Stand the tanks in place. Pentair warns never to turn the resin tank upside down or lay it on its side, because loose media can get into the valve.
4. Cut into the main and fit the bypass. Run pipe or flexible connectors from the main to the bypass on the valve. Do not support the system's weight on the plumbing.
5. Match inlet and outlet. On a cut softener loop, SoftPro's guide says to crack the main slightly: the pipe that flows is the supply, which goes to IN.
6. Restore the electrical ground. Where plastic interrupts metal pipe, QWT's guide calls for an approved ground clamp with no less than #6 copper wire across the gap.
7. Run the drain line. Clamp 1/2-inch tubing to the valve's drain fitting and route it to a floor drain, standpipe or laundry tub, ending in an air gap.
8. Run the overflow line. Connect separate tubing from the brine tank overflow fitting to the drain, running downhill.
9. Connect the brine line between the brine tank and the valve.
10. Open the water slowly. Pentair says to fill the media tank slowly so resin does not leave the tank, then purge air at a cold tap.
11. Program the valve. Enter time of day and hardness in grains per gallon; SoftPro's guide says to divide a mg/L result by 17.1.
12. Add water and salt, plug in, and check for leaks. Switch the water heater back on once soft water is flowing.

How should the drain and overflow lines be run?

Run the drain line to an open receptor with an air gap, never straight into a pipe. Pentair's manual says the gap must be 2 pipe diameters or 1 inch, whichever is larger, and warns that inserting the line into a drain, sewer or trap risks sewage being back-siphoned into the softener. State code can be stricter; Massachusetts 248 CMR 10.12 requires an indirect-waste air gap of at least twice the drain's diameter.

Where the drain is lower than the valve, Pentair calls for a 7-inch loop at the far end of the line to act as a siphon break. The overflow line works by gravity, so it must never rise above its fitting, and it must be a separate line with its own air gap.

Septic owners have a few extra checks. University of Maryland Extension advises against connecting softener backwash to the septic tank, while Purdue Extension describes an Indiana rule letting recharge water go to a soil absorption field. WQA's septic toolkit recommends high-efficiency, demand-initiated units. Follow your local code.

How do you start up a new softener?

Start-up depends on whether the resin arrives pre-charged. The Fleck manual walks the valve through backwash, brine draw and rinse by hand, while QWT and SoftPro say their pre-loaded systems need no manual regeneration.

SoftPro's guide says to open the bypass inlet only about a quarter turn until the tank fills, then open the outlet slowly and run a cold soft-water tap until it clears. Test hardness at a cold tap afterward; our guide to how a water softener works explains the cycle you just started.

Install errors that cause callbacks

Choosing a DIY-friendly system

Choose a system that ships with a bypass and quick-connect fittings. The SoftPro ECO City includes a pre-installed bypass, and QWT includes a 3/4-inch plastic bypass with its Fleck 5600SXT, which it states installs in about 2 hours. Our best whole-house water softeners roundup lists what each pick includes, and our well water picks cover iron filters that mount ahead of the softener.

Related guides

• Best picksBest water softeners for iron and sulfur
• GuidesHow long do water softeners last?
• GuidesWater softener resin replacement

Common questions