Flow switches are used in spas and hot tubs to tell the system to turn on and off. A damaged or defective flow switch will keep the spa from receiving electricity. If you receive an error code when you try to turn the hot tub or spa on, troubleshooting the flow switch can help indicate where a problem exists.
Turn the unit off and unplug it from the power source for 30 seconds. This resets the spa's control panel and will make the switch work again. If this does not work, turn the unit off again before trying any other troubleshooting techniques.
Ensure the flow switch valve is open. If it is not open, disconnect the cable and wait for six seconds. Plug the cable back in and check the valve again. While you are checking the valve position, check the valve to make sure there are no obstructions. If anything is stuck in the valve holding it open, the unit will not work properly. Remove the obstruction and try to turn the unit on.
Look at the water level in the hot tub. If the water level is lower than the jets, the flow switch will not work. The spa's manual will indicate how many gallons the spa will hold and how high the water level should be to function properly.
Clean out the filter. Obstructions in the filter will stop the water flow and cause the flow switch to cut off power. Remove the obstruction and turn the unit on.
Check the output pressure and input pressure of the spa's jets and filter. The appropriate pressures for each unit are written in the manual. If the PSI levels are not set to the right pressures, the unit will not work.
Confirm the LED indicator light under the pack cover is wired correctly. If the light is off, the light needs to be rewired. Instructions for the correct wiring are located in the owner's manual or on the manufacturer's website.
Check for leaks in the tank's enclosure. If there are leaks, inspect the grommet and conduit fittings. Replace or tighten any that are leaking. If the conduit fittings and grommet are not leaking, the flow switch is damaged and needs to be replaced.