Marlo Valve Head O-Ring / Tank Neck Seal Leak

Softener leaks water from around the control valve head on top of the mineral tank

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Damaged tank O-ring, Cracked mineral tank neck, Loose valve mounting, Over-tightened plumbing stressing valve

How to Fix / Troubleshooting

Safety first: Place the unit in bypass and depressurize by opening a faucet. Unplug the softener before removing the valve head.

Step-by-step checks:

  • 1. Identify leak source: Dry the area and observe where water emerges—between valve and tank, from fittings, or from the valve body itself.
  • 2. Tighten fittings: If leaks are at threaded inlet/outlet fittings, gently tighten them. Do not overtighten plastic fittings.
  • 3. Remove valve head: If the leak is at the tank neck, carefully disconnect plumbing and lift the Marlo valve head off the mineral tank. Inspect the large tank O-ring for cuts, flattening, or chemical damage.
  • 4. Inspect tank neck: Check the fiberglass or plastic neck for cracks. A cracked neck usually requires tank replacement.
  • 5. Replace and lubricate O-ring: Install a new Marlo tank O-ring, lightly lubricated with NSF-approved silicone grease. Re-seat the valve head evenly and reconnect plumbing.

When to replace parts: Replace the Marlo tank O-ring if damaged. If the tank neck is cracked, replace the entire Marlo mineral tank.

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Repair Difficulty

Hard 4/5

Required Part

Marlo tank O-ring
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