Jandy® R0013203 Water Pressure Switch for JXi™ Heaters 7 PSI - This water pressure switch is for use with JXi™ Heaters. The water pressure switch senses whether or not water is available to the heater by measuring back pressure at the header inlet. If insufficient pressure is detected, the display will indicate a "Check Flow" fault and combustion will stop. Please see your pool heater's manual to ensure you are using the proper part.