how to fix water sw open on pool heater

The “Water SW Open” error message on a pool heater typically indicates a problem with the water flow or pressure switch. This switch is a safety feature that ensures there is adequate water flow before the heater’s ignition sequence begins. If the switch is open, it means that there isn’t sufficient water flow, and the heater won’t operate to prevent potential damage.

Here’s a step-by-step guide to help you diagnose and potentially fix the “Water SW Open” error on your pool heater:

Tools and Materials You’ll Need:

  • Screwdriver
  • Multimeter (optional)
  • Garden hose (if needed for cleaning)
  • Filter cartridge cleaner (if needed)


  1. Safety Precautions:
    • Before you begin any troubleshooting, turn off the pool heater and ensure it is not in operation. Disconnect the power source to the heater to prevent any accidents.
  2. Inspect Water Flow:
    • Check the pool’s water circulation system, including the pump, filter, and skimmer baskets, for any signs of blockages or obstructions that may restrict water flow. Clear any debris or blockages that you find.
  3. Check Water Level:
    • Ensure that the pool’s water level is adequate. If the water level is too low, it can affect the water flow through the heater. Adjust the water level to the recommended level for your pool.
  4. Inspect the Pressure Switch:
    • Locate the pressure switch on the pool heater. It is usually near the water inlet or outlet. Examine the switch and its wiring for any visible damage or loose connections. Tighten any loose wires or connectors.
  5. Test the Pressure Switch (Optional):
    • If you have a multimeter and are comfortable using it, you can test the pressure switch for continuity to confirm whether it’s functioning correctly. Set the multimeter to the continuity (Ohms) mode and test the switch by gently blowing into the hose connected to the switch. If the switch doesn’t register continuity when it should, it may be faulty and require replacement.
  6. Clean the Filter Cartridge (if applicable):
    • A clogged or dirty filter can reduce water flow and trigger the “Water SW Open” error. If your pool has a filter cartridge, clean or replace it as needed to ensure proper water flow.
  7. Check for Air Bubbles:
    • Air bubbles in the pool water can affect the pressure switch’s operation. Ensure that there are no air leaks in the system, particularly around the pump and filter connections. Tighten any loose connections and ensure that the pump is properly primed.
  8. Restart the Heater:
    • After performing the above steps, restart the pool heater and check if the “Water SW Open” error message persists. If the issue is resolved, the heater should function as expected.
  9. Consult a Professional (if necessary):
    • If the error message continues even after performing the troubleshooting steps, or if you are uncomfortable working with pool heater components, it’s advisable to contact a professional pool technician or a heater manufacturer’s service representative to diagnose and repair the issue.

Remember that pool heater maintenance and troubleshooting should be performed with caution, especially when dealing with electrical components. Always follow safety precautions and, if in doubt, seek professional assistance to ensure the safe and efficient operation of your pool heater.

Related Articles

Leave a Reply

Back to top button