Pentair IntelliChlor: Red FLOW Light
Quick Summary
- The red FLOW light indicates the IntelliChlor is not detecting sufficient water flow through the cell.
- Without adequate flow, chlorine production stops to prevent dangerous gas buildup.
- Common causes: pump off or not primed, clogged filter, closed valves, or debris in the cell.
- Check that the pump is running and producing flow before investigating other causes.
- A dirty filter is the most common flow restriction - clean or backwash as needed.
What the Red FLOW Light Means
The IntelliChlor incorporates a flow sensor that detects water movement through the cell. When flow is insufficient or absent, the red FLOW light illuminates and chlorine production immediately stops. This is a critical safety feature - operating the electrolytic cell without water flow would create dangerous chlorine gas buildup.
Common Causes
Pump Not Running
The IntelliChlor only operates when water is flowing. If the pump is off, the FLOW light will be red. This is normal behavior - the system is designed to only receive power when wired to the load side of the pump circuit or time clock.
Pump Has Lost Prime
If the pump is running but has lost prime (no water in the pump basket, pump making loud noises, no water visible in the strainer lid), there's no actual flow through the system. Re-prime the pump to restore flow.
Dirty or Clogged Filter
A filter that needs cleaning or backwashing is the most common cause of restricted flow. Check your filter pressure gauge - if it's 8-10 PSI above the clean starting pressure, the filter needs service.
Closed or Partially Closed Valves
Check all valves between the pump and the IntelliChlor cell. A valve that's accidentally closed or partially closed will restrict flow. This includes return-side valves and any valves used for pool/spa switching.
Debris in the Cell
Leaves, debris, or other obstructions that have made it past the strainer baskets can lodge in the IntelliChlor cell, blocking water flow. Remove and inspect the cell.
Clogged Skimmer or Pump Baskets
Full baskets restrict suction flow. Empty the skimmer basket(s) and pump strainer basket regularly.
Troubleshooting Steps
- Verify pump operation: Is the pump running? Can you see water moving in the pump lid? Is the pump making normal sounds?
- Check strainer baskets: Empty the pump basket and skimmer basket(s)
- Check filter pressure: If high, clean or backwash the filter
- Verify valve positions: Ensure all valves are fully open
- Inspect the cell: Remove and check for debris blocking the flow path
- Prime the pump: If pump lost prime, refill and re-prime
Variable Speed Pump Considerations
If you use a variable speed pump, ensure it's running at sufficient RPM when the IntelliChlor is supposed to operate. Very low speeds may not generate enough flow to trigger the flow sensor. Most IntelliChlor installations require at least 20-30 GPM flow rate.
When to Call a Professional
If you've verified the pump is running with good flow through the system but the FLOW light remains red, the flow sensor inside the cell may be faulty. A technician can test the sensor and determine if the cell needs replacement.