How to Fix the "LF" Error on Your Hot Tub

How to Fix the "LF" Error on Your Hot Tub

An "LF" (Low Flow) error indicates that there is insufficient water moving through the heater. This is a critical safety feature designed to protect your spa's heating element from overheating or "dry-firing."

? Troubleshooting Checklist

1. Check & Clean Filter

The most common culprit is a dirty filter. Remove the filter(s) and run the spa briefly without them. If the error clears, your filter is clogged and needs a deep clean or replacement.

2. Verify Water Level

If your water is too low, the pump will suck in air. Ensure the water level is 2-3 inches above the highest jet or at the midpoint of the skimmer opening.

3. Inspect for Flow Restrictions

  • Check the skimmer, suction fittings, and pump impeller for debris or blockages.
  • Ensure all plumbing valves (slice valves) are fully open (pulled up).

4. Bleed Air from the System (Prime)

Air trapped in the lines (an "airlock") can stop water flow. Turn the pump off and on several times to dislodge the air. If your spa has a bleed valve on the pump, use it to release any trapped air until a steady stream of water appears.

5. Assess the Pump

If the above steps don't resolve the error, the pump may be failing, have a bad capacitor, or have a significant internal obstruction requiring professional attention.

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Feb 7th 2026

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