IXI & JXi Heater Check Flow Fault – Causes & Fixes

The Check Flow fault on AstralPool IXI and Zodiac JXi gas pool heaters means there is insufficient water flow through the heater.

This is one of the most common IXI and JXi heater faults and is usually caused by a restriction in the pool system, low circulation, or a pressure-switch related issue.

A Check Flow fault is one of the main reasons an IXI or JXi heater is not heating properly.

Common Causes

• Blocked pool filter or pump basket
• Closed valves or incorrect plumbing
• Air in the system
• Low pump performance
• Faulty pressure switch

If low flow continues, it may also trigger related faults such as a High Limit fault due to overheating inside the heater.

How to Fix It

• Clean filter and pump basket
• Check all valves are open
• Prime the pump
• Inspect the pressure switch
• Confirm strong return flow

Common Heater Problems

• Heater Not Heating
• Heater Not Igniting
• Heater Keeps Turning Off

Related IXI & JXi Troubleshooting

• IXI & JXi Gas Heater Error Codes Guide
• Ignition Fault
• High Limit Fault

When to Book a Heater Repair

If the Check Flow fault remains after restoring water circulation, the heater may need a pressure switch or internal repair.

Book a Heater Service or Repair →

This article is for general information only. HeaterFix recommends all gas heater servicing, repairs and replacements be carried out by a qualified licensed gas fitter.