Pentair Internal Valve Blockage / Piston Failure

No water to house when softener is in service; water returns when bypassed.

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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

Collapsed or swollen seals and spacers, Broken rotor/piston in Pentair valve, Severe iron or debris blockage, Incorrect plumbing to inlet/outlet

How to Fix / Troubleshooting

Safety: Immediately place the softener in BYPASS to restore water. Shut off inlet and relieve pressure before disassembling the valve.

  • Confirm plumbing: Verify that the inlet and outlet are not reversed on the Pentair valve body.
  • Inspect valve internals: Remove the control head from the mineral tank. Examine the rotor/piston and seals for swelling, tearing, or disintegration.
  • Clean debris: Flush out any sand, iron sludge, or resin beads that may have migrated into the valve.
  • Rebuild valve: Install a Pentair seal and spacer kit and, if damaged, a new Pentair rotor/piston assembly for your valve model.
  • Reassemble and test: Reinstall the valve, slowly open the inlet to pressurize, and return the bypass to SERVICE. Check for normal flow.
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Repair Difficulty

Hard 4/5

Required Part

Pentair valve seal and spacer kit
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