Pentair Pool Heater Error Code 16: How to Fix It
Medium 30–90 minutes High Severity
Verified June 2026
- Error Code
- 16
- Brand
- Pentair
- Product Type
- pool_equipment
- Severity
- High
- DIY Difficulty
- Medium
- Estimated Fix Time
- 30–90 minutes
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Tools You'll Need
- Multimeter
- Phillips screwdriver
- Flathead screwdriver
- Garden hose (for filter cleaning)
- Replacement pool filter cartridge (if needed)
- Needle-nose pliers
- Insulated gloves
How to Fix Error Code 16
-
Turn Off the Heater and Allow It to Cool
Do not attempt to bypass or jumper the high-limit switch. It is a critical safety device. Bypassing it can result in fire, explosion, or severe equipment damage. -
Check Pump Operation and Water Flow
-
Inspect and Clean the Filter
-
Verify the Flow/Pressure Switch
Turn off the heater power before probing the flow switch with a multimeter. Only test the switch terminals, not the main power supply terminals. -
Inspect the High-Limit Sensor Itself
Power off and unplug or disconnect the heater from its electrical supply before testing or removing the high-limit sensor. -
Check for Blocked or Dirty Heat Exchanger
Do not use harsh acids or chemicals inside the heat exchanger without professional guidance, as this can damage the tubes and cause leaks. -
Confirm Adequate Gas Pressure (Gas Heaters Only)
Never attempt to repair, adjust, or tamper with gas lines, regulators, or gas valves yourself. Gas work must be performed by a licensed professional. -
Reset the Heater and Test
If the error returns immediately after reset without the heater running, the high-limit sensor itself is likely faulty and requires replacement.
Parts You May Need
High-limit sensor
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Flow switch / pressure switch
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Pool filter cartridge
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Pool pump basket
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High-limit sensor
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Flow switch / pressure switch
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Pool filter cartridge
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Pool pump basket
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High-limit sensor
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Flow switch / pressure switch
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Pool filter cartridge
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Pool pump basket
Check Price on Amazon
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When to Call a Professional
Call a licensed pool heater technician if: the high-limit sensor tests faulty and you are not comfortable replacing it yourself; the heat exchanger has heavy scale buildup requiring professional descaling; you suspect a gas pressure or gas supply issue (always requires a licensed gas technician); the error persists after checking flow, the filter, and the sensor; or the heater is still under warranty and opening it yourself may void coverage. Any time you smell gas near the unit, shut off the gas supply immediately and call your gas utility and a licensed technician — do not attempt to diagnose it yourself.Frequently Asked Questions
What does Error Code 16 mean on a Pentair pool heater?
Error Code 16 means the high-limit switch has tripped. This is a safety feature that shuts the heater down when it detects that water or internal temperatures have exceeded a safe limit. The most common causes are low water flow, a clogged filter, a faulty flow switch, or a failed high-limit sensor.
Can I reset Pentair Error Code 16 myself?
Yes, but you should not simply reset it without finding and fixing the root cause first. If you reset the heater without correcting the underlying issue — such as a clogged filter or failed flow switch — the high-limit will trip again immediately. Follow the diagnostic steps above before attempting a reset.
How do I know if my Pentair high-limit sensor is bad?
Use a multimeter set to continuity mode. With the heater powered off and cooled to room temperature, disconnect the sensor wires and probe both terminals. A working sensor at room temperature should show continuity (closed circuit). If the meter shows an open circuit (no continuity) at room temperature, the sensor has failed and needs to be replaced.
Why does my Pentair pool heater keep tripping the high limit?
Repeated high-limit trips usually point to a persistent water flow restriction (dirty filter, undersized pump, partially closed valves), a failing high-limit sensor that trips at lower-than-normal temperatures, scale buildup inside the heat exchanger, or, on gas models, improper gas pressure causing the burner to run too hot. Address each of these in order to find the culprit.
Is it safe to run my pool heater after an Error Code 16?
No — do not continue to run or repeatedly reset the heater while ignoring Error Code 16. The high-limit switch is a critical safety device. Repeated overheating can crack the heat exchanger, damage internal components, and in gas models, create a risk of fire or explosion. Always diagnose and fix the underlying cause before returning the heater to service.