How to Fix Hot Tub Flow Errors

Hands up if you own a hot tub and you wouldn’t have the first idea of how to fix an error? Well, you’ve come to the right place.

Our guide takes you through the various flow errors; what they are, what they mean and how to easily resolve them.

Let’s dive in and get started.

What is a hot tub flow error? 

A hot tub flow error suggests that there’s a problem with the flow of water through your hot tub heater. Some of the most common codes are FLO, FL1 or FL2 for flow or pressure switches. The most common causes are a dirty or damaged filter, low water levels, air in the piping system or a faulty pump or sensor.

What are hot tub flow switches and pressure switches?

Flow and pressure switches monitor the water flow through your tub and act as a safety device. Your heater will automatically turn off once an error is detected or the water flow is interrupted. This safety mechanism has been built to prevent costly damage to your heater and other parts like pumps.

What is the difference between flow error codes?

Hot tub error codes vary between manufacturers and models, so we always recommend checking your instruction manual. That said, the most common error codes are:

  • FL1 indicates an error with the flow switch, which is stuck in the open position.
  • FL2 indicates an error with the flow switch, which is stuck in the closed position.
  • FLO indicates there is an issue with the water flow.

Hot tub flow error troubleshooting

To try and diagnose your hot tub errors, it’s easy to check the following: 

Is the water level too low?

Your water level should be touching the bottom of your spa pillows when no one is in the hot tub. If your tub has no pillows, you’re likely to have a waterline indicator within the shell or the filtration skimmer. The hot tub waterline must meet the minimum requirements as it can lead to not having enough water pumping through your heater.

When did you last clean the filter?

If your filter is dirty, it could be restricting the flow of water around your hot tub. We advise you to clean and soak your filters overnight every ten weeks and rinse weekly to remove large debris.

For more information on maintaining your filters, take a look at our hot tub filter cleaning guide.

When did you last replace the filter?

Even if your filter is clean over time and with every use, the fibres will eventually break down and restrict water flow. We recommend replacing your hot tub filter every 12-18 months; however, they can last even longer if maintained and cleaned regularly. We advise that you use branded hot tub filters to ensure that your tub runs more efficiently and has improved water circulation.

Have you recently refilled or changed your spa water?

If you recently filled your spa, ask yourself, where did you put the hose during filling? Your hose pipe needs to be positioned down the filter housing so that the water fills the internal pipework first. If it’s positioned in the main spa area, it can cause an airlock.

And, just so you know an airlock is a large pocket of air trapped within the pipes of your hot tub. They prevent correct water flow through the hot tub heater and reduce circulation.

Are all the jets / air controls switched on and all diverters in their central position?

If not, they can prevent the flow needed for filtration, leading to problems with circulation and heating.

How to fix common hot tub flow errors 

Once you’ve performed the above checks, you can move on to fixing your issue below:

Increasing the hot tub water level and filter resolutions

If the water level is incorrect, top up your tub with more water until the waterline indicator is reached. Switch off the power, remove the filters, wait around 20 minutes (as this will allow the sensor to clear the fault), switch the power back on and run the jets without the filters to see if it clears the flow issue.

If the flow error clears, switch off the power again, reinstall the filters and switch the power back on. If the flow issue returns, the problem is with the filter, and it will need cleaning or replacing.

Removing an airlock in your hot tub filter

Ensure all jets are open, run the spa pumps without the filters, and see if the airlock clears. If this doesn’t work, try switching the spa off, then running a hosepipe to your hot tub, making sure it is positioned down the filter housing.


If the flow issue still doesn’t clear, you may have a faulty pump or pressure switch. In this case, we recommend calling a technician to help solve your hot tub problem.

Talk to our team of experts and book a hot tub service here.

Parting advice

And that’s how you fix hot tub and spa flow errors.

Need more advice? Give us a call on 01482 212322 or email and we’ll help you out. 

If you’re looking for a new hot tub you can visit our Yorkshire hot tub showrooms, explore our virtual showroom or book a video call with our showroom team.

Stay up to date with our latest products, hot tub guides and updates on Facebook or Instagram.

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