Fixing a Leaking Water Softener

Find the leak first

Water runs downhill and along pipes, so a puddle under the brine tank may start at the valve, and a wet floor by the valve may be from the drain line. Find the source before buying parts.

1. Stop the water. Turn the bypass to its bypass position, or close the main shutoff if the bypass itself is leaking. Pull the valve's plug as well.
2. Dry everything. Wipe the bypass, the inlet and outlet connections, the valve body, the drain fitting, the brine line and the floor.
3. Turn water back on slowly. Return the bypass to service and watch each joint with a dry paper towel. The first wet spot is the source.
4. Run a regeneration if it only leaks sometimes. Some leaks appear only during backwash or brine fill. Fleck's 5600SXT service manual has you inspect the drain seal while the valve is in its backwash position.
5. Check pressure. SoftPro lists household pressure over 60 psi as a leak cause. The Fleck manual says install a pressure-reducing valve if daytime pressure exceeds 80 psi. Follow your own manual's limit.

SoftPro's leak page names the usual suspects: worn bypass O-rings, loose fittings, cracked valve parts and a faulty float.

Bypass and fittings

Start at the bypass and the inlet and outlet connections, the first items on SoftPro's list of leak causes.

Bypass O-rings. SoftPro's fix: shut off water and power, replace the seals, coat them with silicone lubricant, then regenerate and check for leaks. Pentair's 5600SXT manual allows 100% silicone grease only; petroleum-based lubricants are ruled out. Before turning water back on, Pentair says to rotate the two bypass handles 2 to 3 times to help seat the O-rings.

Stuck handles. SoftPro warns not to force a stuck bypass handle; it can crack the valve body. A cracked body has to be replaced.

Threaded and plastic connections. Pentair says use plumber tape on NPT threads and hand-tighten plastic connections, with no pliers or pipe wrenches.

Replacing the bypass. When the body has cracked or the handles no longer seal, the bypass has to go. For Fleck valves, QWT offers a 3/4-inch stainless replacement (sold by Quality Water Treatment, our store) from $120 (October 2026); the store says it has a 3/4-inch female NPT connection and fits most Fleck 5600, 5800, 2510, 9100 and 9000 valves. Our bypass valve guide explains positions and styles.

If the leak is at a soldered joint or the main line, or a pipe needs cutting, call a licensed plumber and follow local plumbing code.

Control valve leaks

A leak from the valve body itself, or water running down the resin tank, points to the valve's seals or a crack.

• Valve-to-tank seal. The Fleck manual has you lubricate the distributor and tank O-rings with silicone only and seat the valve properly. A dry or pinched O-ring here weeps down the tank.
• Drain fitting. The Fleck manual says Teflon tape is the only sealant to use on the drain fitting, and to keep at least 6 inches between the drain line flow control and any solder joint.
• Injector cover. After injector cleaning, a missing or twisted O-ring on the cap leaks. Refit with new silicone-lubricated O-rings; see injector cleaning.
• Internal seals and piston. Worn seals usually leak inside the valve, sending water to drain or letting hard water through, rather than onto the floor. Quality Water Treatment's guide suggests a yearly valve rebuild covering the piston, seals and spacers, using kit #60010307 on the 5600SXT.
• Cracked valve parts. SoftPro includes these in its list. Cracks need the part or the valve replaced; see water softener control valves.

Once the valve is reassembled, Fleck asks for a look at each sealing surface for drips.

Brine tank and overflow

Check the overflow and float before blaming the tank itself.

• Overflow line. Pentair's manual says to attach 1/2-inch ID tubing to the overflow fitting and run it to a drain, never higher than the fitting, and kept apart from the valve's own drain tubing, ending at an air gap. Without one, an overfill spills onto the floor. See the air gap guide.
• Safety float. SoftPro lists a faulty float as a leak cause. If the refill doesn't stop, the float should shut it off; when the float sticks, the tank overfills. For a Fleck brine tank, QWT offers the BV2310-C brine valve assembly, which replaces FL2310BVSC, (sold by Quality Water Treatment, our store), from $60 (October 2026). The store describes it as a security brine valve and float assembly made of a Fleck #500 air check with brine pickup tube, which keeps air from being drawn into the valve, and a Fleck 2310 brine valve (60014) that prevents overfilling.
• Why it overfilled. A float only stops the symptom. QWT points to a clogged injector or a blocked brine line as likely reasons for the extra water; see brine tank full of water.
• Drain line. Check the drain line along its full run. The Fleck manual calls for at least 1/2-inch drain line; the drain line guide covers fittings and air gaps.

If the tank itself is cracked, it needs replacing. For other faults, start at the troubleshooting guide.

Common questions

Parts for this job

Fleck 3/4" Stainless Bypass for 5600, 5800, 2510, 9100 & 9000

Check current options and prices at Quality Water Treatment.

View at Quality Water Treatment

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