What to do if my Pentair ULTRATEMP ETi 220 Heater shows a LOW WATER FLOW alarm?
- CCory Lowe DDSAug 14, 2025
If your Pentair Heater displays a LOW WATER FLOW alarm, first ensure the water circulation pump is running. If it is on, check for sufficient water flow by verifying the filter is clean (backwash if needed) and inspecting/cleaning the pump impeller. Also, make sure any external water bypass around the heater is closed. Finally, with water flowing, test the water pressure switch; if it's open, replace it.