Pentair IntelliChem pH Alarms

The IntelliChem monitors pool pH continuously and triggers alarms when the reading strays outside the configured threshold values. There are three pH-related alarm conditions: pH HIGH, pH LOW, and the pH >7.8 Lockout — which also suspends ORP dosing as a safety measure.

pH alarm thresholds default to High 7.8 and Low 6.8, each with a 5-minute delay before the alarm activates. The recommended operating range is 7.2–7.6 with a default set point of 7.5.

pH Alarm Thresholds

Alarm	Default Threshold	Delay	Set Point Range	Default Set Point
pH HIGH	7.8	5 minutes	7.2–7.8	7.5
pH LOW	6.8	5 minutes	7.2–7.8	7.5
pH >7.8 Lockout	7.8 (range 7.7–8.2)	Immediate	7.7–8.2	7.8

pH HIGH Alarm

The pH HIGH alarm activates when pH has remained above the high alarm threshold (default 7.8) for more than 5 minutes.

Causes

• Acid doser not operating — check doser connections and power
• Acid supply container empty or nearly empty
• Dose size too small to offset aeration-driven pH rise (common with waterfalls, jets, or spa spillovers)
• Daily dose limit reached — system has stopped dosing for the day
• pH Sensitivity set too low — not triggering a full dose

Troubleshooting Steps

1. Check the acid supply container level — refill if low and update the Supplies menu gauge
2. Confirm the acid doser is operating: navigate to the Supplies menu and run a manual dose to verify the pump activates and chemical is flowing
3. Check whether a Dose Limit alarm is also active — if so, clear the limit manually in pH Settings
4. Increase dose size in pH Settings to deliver more acid per cycle
5. Increase filter run time to give the system more opportunity to dose
6. Change pH Sensitivity to "High" — delivers the full dose at 0.2 pH or greater from set point. Or turn Sensitivity "Off" if you are not overshooting

pH LOW Alarm

The pH LOW alarm activates when pH has remained below the low alarm threshold (default 6.8) for more than 5 minutes. pH below 7.0 is corrosive to equipment and irritating to swimmers.

Causes

• Acid dose size too large — overdosing acid
• Mix time too short — system doses again before pH has fully mixed
• Total alkalinity too low — low TA causes pH to swing downward rapidly and resist buffering back up
• pH probe reading incorrectly low — probe may be dirty, cracked, or need replacement

Troubleshooting Steps

1. Reduce the acid dose size in pH Settings
2. Increase the mix time between doses — allows pH to equalize in the pool before the next dose is triggered
3. Test total alkalinity with an independent test kit — target 80–120 ppm. Low alkalinity is the most common cause of pH instability
4. Check the Saturation Index values — total alkalinity and calcium hardness both affect pH stability
5. Run the Probe-Open Test from Diagnostics to confirm the pH probe is functional
6. Clean the pH sensor (see sensor cleaning procedure below) and recheck readings

pH >7.8 Lockout

When pool pH exceeds the lockout threshold (default 7.8, configurable 7.7–8.2), the IntelliChem suspends ORP/chlorine dosing entirely as a safety measure. The display shows pH >7.8 Lockout.

Why ORP Dosing Is Suspended

At high pH, chlorine becomes significantly less effective as a sanitizer — adding more chlorine at pH 7.8+ would increase ORP readings while delivering far less actual disinfection. More importantly, high pH combined with high chlorine can create undesirable chemical conditions. The lockout protects against over-chlorinating an already unbalanced pool.

How to Resolve

1. Dose acid manually to bring pH down below the lockout threshold
2. Allow water to circulate and mix thoroughly
3. Once pH drops below the lockout set point, ORP dosing will automatically resume
4. Note: Bringing pH down often makes the existing sanitizer significantly more effective — you may not need additional chlorine once pH is in range

If pH Keeps Rising Back Above Lockout

• Check for high CO&sub2; outgassing from aeration features (waterfalls, spillovers, jets) — these can drive pH up faster than the acid doser can compensate
• Verify the acid doser is operating correctly and supply is adequate
• Review total alkalinity — high TA causes persistent upward pH drift. Lowering TA (via acid addition during filtration) reduces the rate of pH rise
• Consider increasing the acid dose size or daily dose limit

pH Sensitivity Setting

The pH Sensitivity setting controls how aggressively the IntelliChem doses relative to distance from set point:

• High: Delivers the full programmed dose when pH is 0.2 or more from the set point. Best for pools that are slow to respond.
• Normal (default): Proportional dosing based on distance from set point.
• Low: Smaller doses relative to deviation. Use when pH is consistently overshooting.
• Off: Delivers the full dose regardless of distance from set point. Use when dosing has been insufficient and you are confident the system will not overshoot.

Sensor Cleaning

If pH readings appear inaccurate and calibration offsets (Tweaks) are not sufficient, clean the pH sensor:

1. Turn off AC power to the IntelliChem at the GFCI switch
2. Disconnect the probe connector from the Flow Cell, then unscrew the pH probe
3. Clean the reference junction (white ring at the bottom of the probe) with a soft toothbrush
4. Use household liquid dish detergent to remove oils from the probe tip and body
5. Rinse thoroughly with fresh water
6. If detergent is insufficient: swirl the probe tip in a solution of 5 parts water to 1 part muriatic acid for 10–20 seconds, then rinse immediately with fresh water
7. Reinstall probe and reconnect — recheck pH readings

If readings remain unstable after cleaning, replace the pH sensor (P/N 522186).

Related Guides

• IntelliChem Troubleshooting Guide
• pH/ORP Dose Limit Alarm
• Self-Test, Calibration, and Sensor Cleaning
• ORP Alarms