Hot tub overheating usually comes from one of three things: heat gained from the sun and pump run time (common in summer), poor water flow through the heater (dirty filter, closed valves, low water, an airlock), or a fault such as a failing sensor or a pump stuck on. If your panel shows an OH, OHH, OHS or HL message, the control has already shut the heater or the whole spa down to protect you and the equipment. Stay out, take the cover off, and work through the checks below.
What hot tub overheating error codes mean
Codes vary by control and model year, so your manual is the final word. The table below is taken from the Canadian Spa Company Alberta owner’s manual (2020 UK edition).
| Message | What the manual says it means | What the manual says to do |
|---|---|---|
| OH / OHH (Overheat) | A sensor has detected spa water at 110°F (43.3°C) or higher. The spa shuts down. | Stay out. Remove the cover to cool; it should reset at 107°F. If not, cut power and call your dealer. |
| OHS (Water is too hot) | Water at 110°F; spa functions disabled. | Auto resets below 108°F. Check for long pump run times or high outdoor heat. |
| OHH (Heater is too hot) | A sensor has detected 118°F (47.8°C) in the heater. The spa shuts down. | Press any button to reset once water is below 108°F, then do the flow checks. |
| HL / HFL | A significant difference between the temperature sensors, which could indicate a flow problem. | Check water level, make sure pumps are primed and there is no airlock. |
| LF | Persistent low flow (fifth HL/HFL in 24 hours). Heater shuts down. | Same checks as HL, then press any button to reset. |
| Pump stuck on | A pump appears to be stuck on. Water may be overheated. | Power down the spa, do not enter, contact a dealer or service company. |
Tubs with Gecko controls use their own codes; Canadian Spa’s support page for its 2024 Gecko K300 panel lists HL and OH messages with flow checks.
Why a hot tub overheats
Hot tub overheating in summer: heat creep
A spa can climb past its set point with the heater off. Master Spas calls this heat creep and lists the usual causes: hot, sunny weather, long filter cycles (water moves through the heater and the pump itself makes heat), a spot with no shade, and good insulation that holds heat in. The Alberta manual says the same thing in plainer terms: in extreme heat the spa may overheat from friction in the plumbing, and the fix is a lower set point, a shorter filter cycle, or taking the cover off to cool.
Pump and filter cycle run time
Every hour a pump runs adds heat. The Alberta troubleshooting chart lists filtration duration as a cause of overheating and says to reduce it to the minimum setting during extreme heat.
Dirty filters and low flow
A clogged filter, closed jets, a closed gate valve or low water slows flow, so water in the heater gets hotter than the water in the tub. Canadian Spa’s Gecko support page lists the checks: keep water at the right level, make sure the suction fitting is not blocked, rinse the filter weekly, open the jets and air controls, and confirm the gate valve behind the cabinet is open.
Airlocks after a refill
Trapped air in the plumbing can starve the heater of water. The manual’s response to HL and dry messages is to confirm the pumps are primed and no airlock exists. Our hot tub airlock guide walks through priming mode and bleeding air step by step.
Sensor or pump faults
If the water feels cool but the panel still says OH, or a pump will not shut off, suspect a sensor, relay or board. That is a technician job.
Hot tub too hot? Step by step fix
- Do not get in. Check the water with a separate, accurate thermometer. The CPSC has warned that hot tub thermostats can be off by as much as four degrees.
- Take the cover off so heat can escape. Master Spas also suggests venting the cover overnight by propping the corners.
- Shorten filter cycles and move them to the coolest part of the day or night.
- Rinse the filter, or replace it if worn.
- Lower the set point, open all jets, air controls and valves, and top up to the fill line.
- If you just refilled, run priming mode and bleed any airlock.
- For a fast drop, partially drain and refill with cool hose water (a Master Spas tip), then rebalance chemistry.
- Reset per your manual. If the code returns, turn off power at the disconnect and call for service.
Do not pull insulation out of the cabinet to cool the tub. Master Spas warns it can cause performance problems and may affect your warranty. For shade, timing and economy mode ideas, see using a hot tub in summer. If your problem is the opposite, see hot tub not heating.
Safe temperature and health
The CPSC says hot tub water should never exceed 104°F, and pregnant women should keep to 100°F. The Alberta manual gives the same limit and warns long hot soaks can cause dizziness, nausea and fainting. Anyone who is pregnant, has heart disease, high or low blood pressure, diabetes or another health condition, or takes medication should ask their doctor before using a hot tub. Get out right away if you feel unwell.
When to call a technician
- OH or OHH returns after the water cools and the flow checks are done.
- A pump will not shut off, or the panel says a pump is stuck on.
- Sensor messages (SA, Sb, Sn) persist.
- The breaker or GFCI trips.
Any work inside the equipment bay or on the electrical supply should be done by a qualified spa technician or licensed electrician, and local code has the final word.
Heater, pump and cover specs on tubs we carry
A 240V tub with two 5 HP pumps has more equipment adding heat than a 120V plug and play tub, so it may need shorter summer filter cycles. Specs are from our listings.
| Model | Electrical | Heater | Pump | Insulation and cover | Price |
|---|---|---|---|---|---|
| Canadian Spa Muskoka 5-Person | 120V, 15A | 1.0 kW | 2 speed 1.5 HP | Blackout insulation, 3″/2″ hardtop | $6,000 |
| Canadian Spa Calgary 4-Person | 120V, 15A | 1.5 kW | 2 speed 2 HP | Blackout insulation, 5″/3″ hardtop | $8,449 |
| Canadian Spa Richmond 6-Person | 120V, 15A | 1.5 kW | 2 speed 2 HP | Blackout insulation, 5″/3″ hardtop | $10,249 |
| Canadian Spa Burnaby 6-Person | 240V, 50A | 5.5 kW | 2 x 2 speed 5 HP | Blackout insulation, 5″/3″ hardtop | $13,249 |
| Canadian Spa Victoria 7-Person | 240V, 50A | 5.5 kW Balboa | 2 x 2 speed 5 HP | Blackout insulation, 5″/3″ hardtop | $14,749 |
| American Spas 6-Person 40-Jet Lounger | 240V | 5.5 kW titanium | 1 x 6.0 BHP | Thermo layer blanket, insulated ABS base, tapered cover | $7,300 |
The Calgary and Victoria listings mention Balboa digital controls. See the full Canadian Spa Company range, or start with our hot tub buying guide if you are still choosing a size and voltage.
Frequently asked questions
What does a hot tub OH error mean?
On the Balboa style panels in the Canadian Spa Alberta manual, OH means a sensor has read water at 110°F or higher and the spa has shut down. Stay out, remove the cover, and let it cool. It should reset at about 107°F.
Why is my hot tub too hot when the heater is off?
Sun, hot air and pump run time add heat, and a good cover holds it in. Lower the set point and shorten filter cycles.
Can a dirty filter cause a hot tub to overheat?
Yes. A clogged filter cuts flow through the heater, which can trigger HL, LF or heater OHH messages.
How do I stop hot tub overheating in summer?
Set the temperature lower, run filter cycles at night, shade the tub and vent the cover.
Questions about a tub’s heater or controls? Call us at 866-777-2590, Monday to Friday, 9AM to 6PM PST. We offer free freight shipping on orders of $999 or more, with a $200 flat rate below that. You can also review our return and refund policy.
