Water Softener Bypass Valve Guide

What the bypass does

A bypass is a small valve assembly between your plumbing and the softener's control valve. In the service position, water enters the softener, passes through the resin and leaves softened. In the bypass position, water goes straight from the supply pipe to the house pipe and the softener is cut off, so you can work on it without shutting off the whole house. While it is in bypass, everything you draw is hard water.

The Fleck 5600SXT manual says to always provide a bypass valve if the unit is not equipped with one. Fleck lists three bypass part numbers in that manual: 60049 for the 3/4-inch plastic bypass, 60040 for the 3/4-inch brass, and 60041 for the 1-inch brass. Older or custom installs may use a three-valve bypass instead: three ordinary shutoff valves on the pipes, one on the inlet, one on the outlet and one on a crossover pipe between them.

For a replacement on a Fleck valve, one option is QWT's stainless 3/4-inch Fleck bypass (sold by Quality Water Treatment, our store) with 3/4-inch female NPT connections that, by the store's description, fits most Fleck 5600, 5800, 2510 and 9000 valves, from $120 (October 2026).

Service and bypass positions

Bypass styles look different, so check which one you have before you turn anything.

Fleck plastic bypass. Quality Water Treatment's Fleck guide says the knobs line up with the INLET and OUTLET pipes in normal service. To bypass, rotate both knobs clockwise, in the direction marked BYPASS, until they lock. To return to service, rotate them counter-clockwise and make sure they are fully open; a partly open bypass lets hard water pass.

Three-valve bypass. The Fleck manual gives the order: open the valve in the bypass line first, then close the inlet and outlet valves at the softener. When you return to service, open the inlet and outlet and be sure to shut off the bypass line.

After any change. SoftPro suggests running cold taps for several minutes before using hot-water appliances, which clears air and any stirred-up sediment from the lines.

On a new install, Pentair's 5600SXT manual has you work both handles back and forth two or three times before the water goes on, so the O-rings seat and do not leak. The installation guide has the full start-up order.

When to use bypass

Put the softener in bypass whenever you need to stop water passing through it:

• Service work. The Fleck injector cleaning procedure starts with the bypass; see cleaning the injector.
• Resin beads in the taps. SoftPro says to bypass at once and close the softener valves; see resin beads in the water.
• Pressure checks. SoftPro's test: bypass the softener, and if pressure comes back, the softener is the cause. More in low water pressure.
• Long trips. SoftPro says leave it running for trips under two weeks; for longer ones, use bypass but keep it under 30 days. See vacation mode.
• Freezing weather. SoftPro's winterizing steps start with shutting off the supply and bypassing before draining the tanks.
• Watering and filling. Outdoor water does not need softening. If a hose bib is on the softened side, a short bypass while you fill a pool or water a lawn saves salt, as long as you switch back.

Leaks and stuck valves

Leaks. SoftPro lists worn bypass O-rings as one of the usual causes of a leak near the valve, along with loose fittings, cracked valve parts, a faulty float and pressure over 60 psi. Its repair: water and power off, fresh seals greased with silicone, then a regeneration while you watch the joints. Pentair's manual allows only 100% silicone on O-rings, never petroleum grease. Our page on a leaking water softener covers the other leak points.

Stuck handles. Forcing a bypass that will not turn can split the valve body, SoftPro cautions. Turn off the water so there is no pressure on the seals, then work the handle gently. If it still will not move, or the body is cracked, replace the bypass rather than forcing it.

Hard water after service. A bypass left partly open is one of the simplest causes of hard water. Quality Water Treatment's troubleshooting page puts a bypass left in the wrong position near the top of the list, and the Fleck manual's checklist starts with confirming the bypass is fully in service. SoftPro adds a quick test: if raw and treated water test within 1 to 2 gpg of each other, suspect the bypass. Then work through how to tell if a water softener is working.

Common questions

Related guides

• FixFixing a softener that stays hard
• FixResetting the control after service
• InstallDrain line setup