A salt cell stops producing chlorine for six reasons, in this diagnostic order: salt level below 2,700 ppm, water temperature below 60F, calcium scale on the cell plates, low cell amperage (end of life), cyanuric acid too low so UV destroys chlorine as fast as it is made, or a failed control board. Check salt first; it takes 30 seconds and resolves 40% of cases. Salt chlorine generators are sold as "set and forget" but every operator gets the callback at least monthly. The pool is green, the customer swears they checked salt, and the cell shows "No Chlorine Output." This is the troubleshooting playbook in the order a tech should run through it.
TL;DR
- Check 1: salt level (should be 2,700 to 3,400 ppm depending on cell brand)
- Check 2: water temperature (below 60F most cells shut down automatically)
- Check 3: cell plate condition (visible calcium buildup = clean with 4:1 acid solution)
- Check 4: cell amperage on the control panel (low amps = cell at end of life)
- Check 5: cyanuric acid level (low CYA means chlorine is created but instantly destroyed by UV)
- Check 6: control panel itself (rare but real; bad board can show output when none is produced)
The diagnostic order
Six things can stop chlorine production. The order matters because checking salt first takes 30 seconds and resolves 40% of cases. Most operators skip this and go straight to "cell is dead, replace for $700," which is costly and wrong half the time.
Check 1: salt level
Salt cells need 2,700 to 3,400 ppm of dissolved salt to operate (exact range varies by manufacturer; Hayward AquaRite is 2,700 to 3,400, Pentair IntelliChlor is 3,200 to 4,500). Below the minimum, electrolysis stalls and the cell either runs inefficient or shuts down entirely.
Test salt with a digital salt meter ($30 to $50, far more accurate than test strips). If low, add NaCl pool salt to bring the level into range. Each 40 lb bag of salt raises salt by about 240 ppm in a 20,000 gallon pool.
Salt drops from rain dilution, splash-out, partial drains, and backwashing. Customers who recently had heavy rain or filled their pool are common low-salt cases.
Check 2: water temperature
Most salt cells have a low-temperature cutout at 50 to 60F. When the water dips below the threshold, the cell stops producing automatically to protect itself from inefficient electrolysis. This is normal behavior; not a malfunction.
Fix: if it is early spring or late fall in a cold climate, wait for water to warm or supplement with liquid chlorine. The cell will resume automatically as water warms.
Check 3: cell calcium buildup
Pull the cell from the housing. Look at the titanium plates. If you see visible white crusty buildup between plates, that is calcium scale and it blocks the electrolysis surface. Output drops 30 to 80% depending on severity.
Fix: mix 1 part muriatic acid with 4 parts water in a 5 gallon bucket. Submerge the cell with plates fully covered. Soak 10 minutes. Flip, soak another 10 if buildup is heavy. Rinse with garden hose at full pressure. Return to housing.
How often to clean depends on water hardness. Phoenix and Vegas: every 3 months. Florida: every 6 to 12 months. Some operators inspect monthly during routine visits.
“Visible white buildup on cell plates is the #1 fixable cause of low chlorine output. Costs $5 in acid; saves a $700 cell.”
Check 4: cell amperage on the control panel
Most modern salt control panels have a diagnostic mode showing cell amperage and voltage. Healthy cells run within a specific range (Hayward AquaRite: 5 to 8 amps, Pentair IntelliChlor: 4.5 to 5.5 amps). Low amperage at full output setting indicates a degraded cell.
If amps are healthy but production is low, the cell is producing chlorine but something else is destroying it before you can measure FC. Move to Check 5.
If amps are below the minimum threshold, the cell is at or near end of life. Replacement runs $400 to $900 in parts.
Check 5: CYA destroying chlorine
A working cell can produce 1 to 2 lbs of chlorine per day. If CYA is below 30 ppm, UV destroys it as fast as the cell produces it. The customer sees zero FC at testing and the cell shows "low output" because effectively, the output is being burnt off.
Fix: test CYA. Salt pool target is 70 to 80 ppm. Add granular stabilizer to bring into range.
Check 6: control panel itself
Rare but real. The control panel can fail in a way that reports "production on" without actually triggering the cell. Symptoms: cell amperage shows zero on the diagnostic readout, but the panel says "active." Either the relay is stuck open, the time clock is wrong, or the board is failing.
Fix: this is a service call for the manufacturer (Hayward, Pentair, Jandy). Board replacement runs $300 to $600 plus 1 to 2 hours labor.
When to recommend a cell replacement
Cells have a 3 to 7 year lifespan. Replace preventively when:
- Cell is 5+ years old AND output is dropping despite cleaning + correct salt level
- Amperage at full output is below minimum threshold by more than 15%
- Visible plate degradation: gray/scaly plates that do not clean back to bright titanium
- Customer is preparing the pool for peak summer use; a failure mid-July costs more than a planned replacement
Standard residential cell replacement: $400 to $900 for cell hardware (Hayward T-Cell-15: ~$500, Pentair IC40: ~$800), plus 1 to 2 hours labor at $75 to $125/hr.
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