Hayward Sense & Dispense No Chlorine: Why Your Pool Isn't Being Sanitized
Quick Summary
- The Sense & Dispense uses ORP to control chlorine production. If ORP reads at or above the setpoint (default 650 mV, high alarm at 850 mV), the chlorinator shuts down — even if free chlorine is actually low.
- The flow switch in the probe cell must be closed before the system will allow chlorination. A stuck-open flow switch or low flow stops production entirely.
- A CSM Comm Error between the OmniLogic and the chemistry controller module will prevent the OmniLogic from commanding the chlorinator at all.
- Low salt (below 2,700 PPM) or a scaled/expired TurboCell reduces or eliminates chlorine output independent of what the Sense & Dispense is commanding.
How ORP Controls Chlorination
The Sense & Dispense does not measure free chlorine directly. It uses ORP (Oxidation-Reduction Potential), measured in millivolts, as a proxy for sanitizer activity. When ORP is below the setpoint (default 650 mV), the system commands the TurboCell on. When ORP reaches the setpoint, the cell is shut off. If ORP rises above 850 mV (the high alarm threshold), the cell is locked out until ORP drops.
This means a pool can have low measurable chlorine while ORP reads high — common in pools with high cyanuric acid (CYA) levels, which depress ORP even when total chlorine is adequate. It also means a pool can be under-chlorinated if the ORP probe is reading artificially high due to a dirty or failed probe.
Step-By-Step Troubleshooting
Step 1: Check the OmniLogic screen for active alarms
At the Home Screen, look for any chemistry alarm indicators. Navigate to the Sense & Dispense status screen and note:
- Current ORP reading and ORP setpoint
- Current chlorinator output percentage (if shown)
- Any active alarms: CSM Comm Error, Flow Switch, Cell Low, ORP High, ORP Low
If a CSM Comm Error is active, the OmniLogic cannot communicate with the chemistry module — resolve that first before diagnosing chlorine output. See the CSM Comm Error article for diagnosis steps.
Step 2: Confirm ORP is actually below setpoint
If ORP reads at or above the setpoint, the system is correctly holding the chlorinator off. The question then becomes whether the ORP reading is accurate:
- Test free chlorine and ORP independently with a calibrated DPD test kit and a handheld ORP meter.
- If the OmniLogic ORP reading is significantly higher than the handheld reading (more than 30–50 mV), the probe may be dirty or failing. Clean the ORP probe and recalibrate.
- If ORP reads accurately high while free chlorine is low, the pool may have elevated CYA (stabilizer) suppressing chlorine effectiveness. CYA above 80 PPM significantly depresses ORP even at normal chlorine levels.
Step 3: Verify flow switch operation
The probe cell contains a flow switch that must close before the Sense & Dispense will enable chlorination. Check the following:
- Confirm the filter pump is running and the system is in normal filtration mode (not backwash or recirculate).
- Verify the probe cell influent valve is open. The cell requires 0.8–2.2 GPM flow; the ideal rate is 1 GPM.
- On the OmniLogic Sense & Dispense status screen, check whether the flow switch reads as closed. If it reads open with the pump running, see the Flow Switch Errors article.
- Inspect the probe cell for debris blocking the flow path. The cell can be removed, inspected, and flushed if flow is suspected to be restricted.
Step 4: Confirm ORP control is enabled in configuration
In the OmniLogic Configuration Wizard, navigate to the Sense & Dispense setup and verify:
- ORP Control: Must be set to Enabled. If disabled, the system monitors ORP but does not use it to control the chlorinator.
- ORP Setpoint: Default 650 mV, adjustable 400–900 mV. If the setpoint was inadvertently set very high (e.g., 900 mV), the system may not call for chlorination under normal pool conditions.
- Chlorinator assignment: The TurboCell must be assigned to the Sense & Dispense in configuration. If it is set to Manual or Schedule control only, the Sense & Dispense ORP readings will not command it.
Step 5: Verify salt level and TurboCell output
Even if the Sense & Dispense is correctly calling for chlorination, a low salt level or degraded cell limits actual output:
- Test salt level with a calibrated salt meter or test strips. The TurboCell requires 2,700–3,400 PPM salt; 3,200 PPM is optimal.
- Check the TurboCell diagnostic screen on the OmniLogic for "Cell Low" or "No Salt" indicators.
- Inspect the TurboCell blades for calcium scale. Heavy scale significantly reduces chlorine production. Acid wash per Hayward guidelines if scale is present.
- Check the TurboCell usage hours. Most residential cells are rated for 5–7 years or approximately 10,000 hours of use. An expired cell produces little or no chlorine regardless of salt level.
Step 6: Check the ORP timeout setting
The ORP timeout prevents the chlorinator from running continuously if ORP never reaches setpoint (for example, during a large chlorine demand after a pool party). The default timeout is 47 hours — if the system was reset or reprogrammed, confirm this timeout is set appropriately and has not triggered a lockout condition. After a timeout-triggered lockout, the system requires manual acknowledgment to resume normal ORP control.
Frequently Asked Questions
The OmniLogic shows ORP at 700 mV but free chlorine tests at 0.5 PPM. How is that possible?
High cyanuric acid (CYA/stabilizer) is the most common cause. CYA binds to free chlorine and reduces its electrochemical activity, causing ORP to read higher than the chlorine level would suggest. If CYA is above 80 PPM, the ORP reading no longer reliably correlates with chlorine effectiveness. Reduce CYA by partial drain and refill, and recalibrate your target ORP setpoint to a lower value (around 600–620 mV) to compensate.
The ORP is at 580 mV (below the 650 mV setpoint) but the chlorinator still isn't running. What else could be stopping it?
Check the flow switch status first — if the flow switch reads open, the system will not allow chlorination regardless of ORP. Then check for a CSM Comm Error, which prevents all chemistry commands. Also confirm the chlorinator output percentage is set above 0% in the TurboCell configuration, and verify there is no active ORP timeout lockout requiring manual reset.
Salt tests at 3,200 PPM but the TurboCell still shows Cell Low. Why?
The OmniLogic reads salt level from the TurboCell's internal sensor, not from an external test. If the cell is scaled, the internal sensor may read low even when the pool water salt level is correct. Acid wash the TurboCell to remove scale and allow the sensor to read accurately. If the reading remains low after cleaning, the cell's internal sensor may be failing and the cell may need replacement.
Can I temporarily bypass ORP control and run the chlorinator on a fixed schedule?
Yes. In the OmniLogic Configuration Wizard, you can change the chlorinator control mode from ORP to Schedule or Manual. This allows the TurboCell to run on a fixed schedule independent of ORP readings, which is useful when diagnosing whether the Sense & Dispense system itself is the problem. Remember to return the setting to ORP control once the issue is resolved.