5 Common Hot Tub Problems and How to Fix Them
Find your symptom, then do the first check
On the left is what you notice. On the right is the one thing to check first. Select a symptom for the full steps.
-
1
The water is cloudy, foamy or green
First check
Test the pH and sanitiser, then rinse the filter.
-
2
The tub is not heating
First check
The thermostat setting and the heating mode.
-
3
The jets feel weak
First check
The water level against the mark on the filter.
-
4
The panel shows a flow message
First check
The water level, then whether the pumps are primed.
-
5
The power trips
First check
Reset the RCD once, then see whether anything else shares its supply.
The water is cloudy, foamy or green
Start by testing the pH and the sanitiser level and correcting whichever is off, then retest after two hours.3 Cloudiness often has a simple cause: the tub has been left unused, the circulation pump has stopped running, chemicals have not fully dissolved or the filter is due a clean.4
Foam usually means oils, lotions, soaps or detergents are changing the pH, and rebalancing the water clears it.3 Green water is a sign of algal growth,4 so the sanitiser level and a freshly cleaned filter come first.
Our cloudy, foamy or green water guide has the full step-by-step fix for each.
The tub is not heating
Work down this list in order, starting with the simplest checks.
AquaSPArkle Immerse Hot Tub Filter Cartridge Cleaner Aqua Sachet£3.99
For the filter check: dissolve a sachet in a bucket of clean water, soak the rinsed filter overnight, then rinse it and let it dry before refitting. Use it every 4 to 6 weeks, with a rinse each week in between.
If all five are in order, the heater element, thermostat or pressure switch is next,6 and your dealer or a service engineer can check them.
Thermostat and mode
Set the temperature above where the water is now. On a tub with a Balboa control system, Economy and Sleep modes heat only during the filter cycles, while Standard mode heats continuously.5
Water level and trapped air
Top the tub up to the level mark and fill it fully, so no air is left in the pipework.1
Breaker
A tripped breaker cuts power to the heater completely, so check the supply is on and reset it once if it has tripped.6
The jets feel weak
Weak jets usually come down to how easily water reaches the pump, so these checks run from the quickest to the least obvious.
- Water level
- Top the water up to the level mark on the filter faceplate.2
- Jet valves and faces
- Open any jet valves, diverters or comfort-control lever, and turn each jet face to open.21
- Suction fitting
- Clear any debris by hand or with a spa vacuum.2
- Air in the pump
- Air gets in through the way the tub was filled, and the priming steps in your manual release it.3
The panel shows a flow message
A flow message, often shown as FLO, tells you not enough water is moving through the heater. On a Balboa system, if it keeps coming back the heater switches off while the pumps and jets carry on,5 so it can show up alongside a tub that has stopped heating.
Check the water level first. If the level is right, make sure every pump is primed.5 Our guide to fixing hot tub flow errors has the full step-by-step fix.
The power trips
Reset the RCD once and see whether the tub runs. Common causes of a trip are a worn heater element, loose or corroded connections, moisture in components and other appliances sharing the tub's supply, and a hot tub should have its own dedicated circuit.7
If it trips again straight away, leave it switched off and have a qualified electrician inspect it.27 Our hot tub electrical installation guidelines show how the supply should be set up, and the hot tub safety guide covers staying safe around the tub.
Quick answers
Open a question to read the answer.
Why is my hot tub not heating?
Start with the thermostat setting and heating mode, then check the filter, the water level, the breaker and any reset button or high-limit sensor on your tub. If all of those are fine, your dealer or a service engineer can check the heater element, thermostat and pressure switch.
Why are my hot tub jets weak?
The usual causes are a low water level, dirty filters, closed jet valves, a blocked suction fitting or air in the pump. Work through them in that order, and use the priming steps in your manual to release trapped air.
What does a hot tub flow error mean?
It means not enough water is moving through the heater, so the tub switches the heater off. Check the water level first, then make sure the pumps are primed and the filters are clean.
Why does my hot tub keep tripping the RCD?
Common causes are a worn heater element, loose or corroded connections, moisture in components or other appliances sharing the supply. Reset it once, and if it trips again straight away, leave it switched off and call a qualified electrician.
Why is my hot tub water cloudy?
Cloudy water usually comes from unbalanced pH or sanitiser, a dirty filter, a pump that has stopped circulating or chemicals that have not fully dissolved. Test and correct the water, rinse the filter and retest after two hours.
How often should I clean my hot tub filter?
Rinse it once a week and give it a full soak clean with a filter cleaner every 4 to 6 weeks.
Sources
- Hot Spring Spas, Fix your hot tub with this complete troubleshooting guide, 12 November 2025
- Bullfrog Spas, Troubleshooting and FAQs, 16 May 2025
- Bullfrog Spas, Common hot tub problems (and solutions), updated 22 April 2025
- HSE, The control of legionella and other infectious agents in spa-pool systems (HSG282), 2017
- Balboa Water Group, Balboa 500DZ-Series operation guide, 27 September 2011
- Hydropool, Why is my swim spa not heating?, 16 January 2026
- Hydropool, Hot tub keeps tripping breaker: what to do, 12 December 2025
Paul Margerison
Managing Director & Founder, Outdoor Living
Most hot tub problems have a simple first check. This guide puts that check beside each symptom so you can start in the right place.
Rather we did it for you?
Our own service team visits hot tubs anywhere in the UK. Book online, then we call you to pick a date.
-
Diagnostic visitA technician finds and explains the fault. Any parts or repairs are quoted first.
£129View service
-
Annual hot tub serviceA 32-point check, a drain and clean, and a photo report. About two hours.
£179View service
-
Drain, clean and fillDrained, cleaned inside and out, and refilled ready to heat. Ideal every 3 to 4 months.
£129View service
