The FLO error (also displayed as FL, FLOW or LF) is the most common hot tub error code that we come across. Today, we will show you how to troubleshoot and fix FLO errors in your hot tub, regardless of the make and model. But first, what causes FLO errors in the first place?

What Causes A FLO Error In A Hot Tub?

All hot tubs have sensors that are used to monitor water flow through the hot tub's heater. This is done to ensure that water is properly flowing when the heater is on. Without proper water flow, the heater could heat the water within it too much; potentially causing damage to the plumbing and surrounding equipment. FLO errors appear when these sensors don't sense enough water flowing through the heater.

Step 1 - Check Water Level

The first step when troubleshooting hot tub FLO errors is to check the water level in the hot tub. If the water is less than halfway up the opening to the skimmer/filter area, there simply may not be enough water flowing through the filtration system. Refill your hot tub to the appropriate level then shut the power down for at least 30 seconds to reset the error code. Turn the hot tub back on. If the FLO error returns, go to step 2.

Step 2 - Check Your Filter

The most common cause of hot tub FLO errors is simply dirty filters. As filters become clogged with debris, they allow less water to pass through them. If they get too dirty they can restrict water flow enough to cause a FLO error.

To fix a FLO error caused by dirty filters simply turn off the hot tub, remove the filters, then turn the hot tub back on. If the FLO error goes away when the filters are out, give them a deep clean and put them back in. If the FLO error returns - or if the filters are over 1 year old - replace the filters.

If removing your filters didn't fix the FLO error, go to step 3.

Step 3 - Check The Pressure Switch

There are 2 main types of flow sensors in hot tubs:

1. Pressure switch. These sensors test the actual water flow within the plumbing. As water moves it pushes two tiny metal plates together, completing an electrical circuit that tells the spa pack that there is water flow.
2. Temperature sensors. This type of flow sensor measures water temperature in two different parts of the hot tub. If temperatures in one sensor exceed a certain threshold, the spa pack will assume there is no water flow, shut the whole system down and display a FLO error.

A pressure sensor (left) and temperature sensor (right)

If your hot tub has temperature sensors, go to step 4. If your hot tub has a pressure switch style sensor you can quickly test to see if it is working by:

1. Shutting the hot tub down.
2. Unplugging the sensor from the spa pack.
3. Running a wire between the two contacts on the circuit board that the pressure switch plugged into.
4. Turning the hot tub back on.

This completes the pressure switch circuit in the spa pack that indicates good water flow. If the FLO error is still there, go to step 5.

If the FLO error is now gone, then it is being caused by the pressure switch. Fortunately, you might still be able to fix it. At the top of the pressure switch is a small screw or dial. Turn it one full turn counter-clockwise, then turn off the hot tub, plug the pressure switch back in (removing the wire connecting the two contacts), and turn the hot tub back on. If the FLO error is still there, go to step 4.

Step 4 - Replace The Sensors

If you've determined that your pressure switch is faulty, or if your hot tub uses temperature sensors, the next thing to do is to replace your sensors. When replacing temperature sensors, we recommend replacing both as there is no way to tell if one or both are broken.

Hot tubs with pressure switches will still have a temperature sensor, though this is just for monitoring water temperature and doesn't need to be replaced.

Step 5 - Replace The Spa Pack / Circulation Pump

At this point we've exhausted all of the easy options. The cause of the FLO error can now be narrowed down to either a faulty spa pack, or a worn out circulation pump (if your hot tub has a circulation pump that is). Replacing one or both of them will fix your FLO error.

After checking everything else, you may have no other choice than to replace your spa pack.

Wrapping Up

Troubleshooting and fixing a FLO error in a hot tub is something that pretty much any hot tub owner can do. The most important thing to remember when fixing a FLO error, or any hot tub error code, it is important to turn off power to the hot tub for at least 30 seconds. This allows the hot tub to fully power down and reset. If you don't turn the power of the hot tub off for 30 seconds or more the FLO error will remain on the screen, even if you've solved the issue.