LO FLO
Raypak Marginal Water Flow Condition

Raypak display alternates between LO FLO and water temperature; unit may start and stop repeatedly.

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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

Partially clogged filter, Undersized circulation pump for Raypak heat pump, Bypass valve incorrectly set, Debris in Raypak internal water passages

How to Fix / Troubleshooting

Safety first: Turn off power to both the Raypak unit and the pool pump before disassembling any plumbing.

  • Fully clean filtration system: Perform a thorough filter cleaning, not just a quick backwash. Inspect cartridges or grids for tears or collapse.
  • Check pump performance: Verify that the pool pump basket is clean and that the impeller is not clogged (remove pump lid and inspect through the opening with power off).
  • Adjust bypass: If a 3‑way valve is used as a bypass around the Raypak unit, adjust it so that most of the flow goes through the heater while still maintaining system pressure. Too much bypass will cause LO FLO.
  • Flush heater: With unions disconnected and water supply available, flush water through the Raypak heat exchanger in both directions to dislodge debris. Reassemble with new gaskets if needed.
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Repair Difficulty

Medium 3/5

Required Part

Heat Exchanger Assembly
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