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Top 5 Hot Tub Heater Problems

March 7th, 2013 by

Hot Tub Won’t Heat?

hot-tub-not-heatingA Hot Tub without heat, is … cold! And no fun for anyone. Hot Tubs are meant to be HOT, and if you’ve ever been in a Warm Tub, you know it’s just not the same.

If you’re in charge of the hot tub at home, you hear the complaints when the hot tub heater is not working properly. You need a quick solution to the problem of no heat, or not enough heat in your spa or tub.

So here we have, a quick guide to the common issues affecting common spa heaters. I won’t go into gas heaters, but restrict this to common spa pack type heaters, or electric immersion element heaters.

Top 5 Spa Heater ProblemsHOT-TUB-PARTS

LOW FLOW: A spa heater relies on sufficient water flow to operate. A pressure switch, screwed into the heater chamber, senses when the water flow is too low to properly protect the heater. It breaks the electrical circuit powering the heater element, and the heater shuts down, and will begin to heat until proper water flow is established. With a flow issue, you don’t normally need any spa heater parts to repair.

Low flow in your spa or hot tub is most commonly associated with a dirty spa filter. If your spa heater won’t heat, remove your spa cartridge and clean the filter(s), to see if you have a pressure or flow rate problem. Other flow problems will be more severe – broken pump impeller, broken valves, or clogged pipes or spa jets. These problems will be evident from the noticeably reduced flow coming into the spa or hot tub.

THERMOSTAT:  The thermostat is the dial that you turn to crank up the heat. Most new spas use a solid state thermostat, connected to a circuit board. If you have a thermostat “knob”, instead of a lighted red arrow, you can test your thermostat to see if the unit is faulty internally, or if the sensor bulb has become corroded.

HIGH LIMIT:   The High Limit is another switch, similar to the pressure switch and thermostat discussed above. It’s purpose is to prevent a run-away spa heater – one that won’t shut off. It has a preset maximum heat (e.g., the upper limit), at which the switch will open, and short the electrical circuit carrying power to your spa heater element.


HOT TUB HEATER ELEMENT: Your heater element is similar to a kitchen cooktop element, only they are built to be immersed in water while operational. Spa heater elements burn out very quickly if operated without cooling water surrounding it. Hot tub elements can also be tested to determine if there is a short in the coating surrounding the heating element.

Spa heater elements can also develop a scale buildup, from hard water or sanitizing with salt systems. When a spa element develops scale on the outside of the element, it will reduce the element’s heat output, and could lead to element failure.


For those of you with newer spas, you’ll often find that your spa heater element is housed in a sleek stainless steel chamber, with unions for easy removal. On this type of spa heater, you can test the element, high limit and pressure switch for resistance, as measured in Ohms. When testing with a multi-meter or ampmeter, an “OPEN” is when the meter spikes to a high reading. A “SHORT” is when there is little to no activity on the meter. When there is no resistance, the current is leaving the circuit, known as a “short-circuit”.


This last category causes profound heartburn to many of our customers. These spa heater problems are causes that you normally don’t think about, but can be a quick solution, and isn’t that what I promised you? Check these causes of spa heater troubles first, for the quickest solution that will have you shaking your head.

  1. GFCI tripped. Look for the electrical outlet on your spa pack. The one with the red TEST button. If it’s popped out, push it back in firmly.
  2. Spa Pack Door Interlock open. Many spas have a switch that is only closed when the spa equipment door is fully inserted and secured.
  3. Spa Cover needs to be replaced. Warped, broken and ill fitting spa covers can allow as much heat to escape as is being put into the tub.
  4. Loose Wires – Connections must be tight and not oxidized. Chewed wires (rodents) is another possibility.

I have sincere hopes that this information has helped you heat your hot tub up again. If you’re still baffled, leave a comment below for me, or give our customer support hotline a call at 800-770-0292.

Happy Hot Tubbin’!

Daniel Lara

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