Most Likely Causes (Ranked)
The brine (salt) tank is usually polyethylene and sits at ambient temperature. Over 10-15 years, the plastic becomes brittle from UV exposure (if near a window) or freeze-thaw cycles (if in a garage). Cracks typically appear at the bottom seam or at stress points near fittings. Salt water is highly corrosive to anything it contacts.
The bypass valve allows water to flow around the softener during maintenance. Its internal O-rings dry out and crack if the valve isn't exercised regularly. When they fail, water leaks from the valve body continuously. This is the most common softener leak in systems over 5 years old.
The resin tank connects to the control valve head via a large O-ring. This O-ring seals water at line pressure. Age, chlorine exposure, and improper reinstallation after service cause it to fail. Water leaks from the joint between the tank and the valve head.
During regeneration, the softener flushes brine and rinse water through a drain line. If this line is kinked, clogged, or the drain flow control is stuck, backpressure causes water to overflow from the brine tank or the control valve weep hole.
Inside the control head, a piston or rotor directs water flow during different cycles. Seals on these components wear from constant pressure and chlorine exposure. Internal leaks may bypass to the drain continuously, or water may weep from the control head body.
How to Fix It
Replace Bypass Valve O-Rings
$5-10 DIY- 1Put the softener in bypass mode. Relieve pressure by opening a nearby faucet.
- 2Remove the bypass valve (it pulls or unclips from the head — consult your model's manual).
- 3Replace the O-rings with the manufacturer's kit (Fleck, GE, Kenmore, Whirlpool all have specific kits for $5-10).
- 4Lubricate new O-rings with silicone grease before installing. Reassemble and test.
Replace the Brine Tank
$50-150- 1A cracked brine tank can't be reliably repaired — the salt water corrodes patches.
- 2Disconnect the brine line from the control head. Remove the brine well and float assembly.
- 3Transfer these components to the new tank. Standard sizes are 14x34 and 18x33 inches.
- 4Reconnect the brine line and fill with salt. Most brine tanks are universal.
Replace the Resin Tank O-Ring
$5-15 DIY- 1Remove the control head from the resin tank (usually a large union or set of bolts).
- 2The O-ring sits in a groove on the tank opening. Remove the old one and clean the groove.
- 3Install the new O-ring (must be exact size for your model), lubricate with silicone grease.
- 4Reseat the control head and hand-tighten the union. Test for leaks.
When to Call a Professional
Salt water is corrosive — wipe up brine spills immediately to prevent floor and equipment damage.
If the resin tank is cracked, the entire softener likely needs replacement ($800-2,000 installed).
Don't ignore a softener leak — the salt water damages concrete, metal pipes, and flooring.
Exercise the bypass valve every 6 months to keep the O-rings supple.
How to Prevent It
Exercise the bypass valve every 6 months by turning it back and forth.
Replace bypass O-rings every 5 years proactively ($5-10 and 10 minutes).
Keep the brine tank out of direct sunlight and freezing temperatures.
Check the drain line annually for kinks or clogs during regeneration.
Frequently Asked Questions
10-15 years for the control head and resin. The brine tank may last 15-20 years. Resin degrades from chlorine — chlorinated municipal water shortens resin life.
Repair if: it's a valve, O-ring, or brine tank issue and the unit is under 10 years old. Replace if: the control head is failing, resin is exhausted, or the unit is 12+ years old.
Possibly. Internal bypass (worn piston seals) can flush brine to drain without softening. Also check the salt bridge (a hard crust over the salt that prevents proper dissolving).
Budget models: $400-600. Mid-range (Fleck, Pentair): $800-1,200. High-end (Kinetico, WaterBoss): $1,500-3,000. Installation: $200-500 if plumbing is already in place.