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Cooling my Hot Tub to Stop Overheating | Spa and Hot Tub Owners Blog.com

Hot Tub and Spa Water- How to Prevent Temperature Overheating on Hot Sunny Days

by Steve

Alex commented with this question about hot tub temperature control in hot weather situations. This can be a problem for outdoor spa installations especially in warm climates. We try cover everyday snags and solutions on the Spa and Hot Tub Owners Blog so I’ve posted it here with my reply as the info may be useful to other hot tub and spa owners who experience similar water temperature problems.

Alex’s question:

Cooling my hot tub.
The weather has been very hot and the temperature on my hot tub keeps going above the set temperature by several degrees and I’m worried about it overheating. Why is this happening and how can I keep it stable in summertime?


I presume that all this is happening when the hot tub cover is in place and it is an outdoor installation. Hot tubs are very well thermally insulated to keep heat inside. You can see this from the thickness of the insulation around the tub and inside the hot tub cover.

Although you may have the temperature set to a maximum of say 98F (38C) and the hot tub heating system turns off when required, there are other factors which can continue the heating process.

On hot weather days the high air temperature will reduce the cooling down period of the spa or hot tub water and there will be a certain amount of heat transfer from the sun shining direct on the cover. It’s acting as a solar collector. With the jets running, the circulating pumps also create heat and all this can create an incubating effect and cause the water temperature to rise without the heater being switched on. This is especially true if the sun is shining on the exposed hot tub cover.

To prevent overheating I would suggest that you could try:

  • Set the spa temperature a few degrees lower than required so the heater element cuts out sooner
  • If the water temperature still rises too high trya very low setting
  • Reduce the amount of pump cycles to a minimum 

The added benefit of this strategy is that you will be conserving energy and using the solar power of the sun to heat your hot tub water even though by accident.

Note:  Simply leaving the cover open is not a good idea because this will have an effect on the water cleaning system by increasing the growth of algae and bacteria.

I hope this was useful. 

I’d love to hear your comments below.

Spa and Hot Tub Owners Blog.com

{ 3 comments… read them below or add one }

Ron Walker July 4, 2012 at 2:02 pm

We live in Bakersfield Ca It gets over 100 degrees some times in the summer the spa will get so hot it shuts down over 110 degrees to do that the spa is set at
80 it is in the sun does anybody make a reflector to put on the spa to keep the temp down


Ron Walker July 4, 2012 at 7:43 pm

up date on spa getting too hot from the sun. Went to Lowe’s bought two panels of 2 inch thick foam insulation with foil glued to one side. I place them foil side up on the spa. I think the foil will reflect the sun and the insulation will help. I Will keep this updated to let every one know if it works


Mike June 18, 2015 at 7:35 pm

Hi Ron

I live in Phoenix AZ and tub is at 112 degrees even with a triangle shade over it. DID the foam do the job?


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