Hot tub & spa or whirlpool bath use, maintenance, troubleshooting & repair:

This article describes the operation, controls, & troubleshooting of heaters used in hot tubs, spas, whirlpool tubs & Jacuzzis.

In these articles we describe the use, operation, maintenance as well as common problems, troubleshooting, & repair suggestions for hot tubs, spas, and whirlpool baths. We discuss hot tub leaks, broken hot tub or spa jets, hot tub or spa water temperature & heater repair, hot tub or spa pump diagnosis & repair, hot tub or spa filter maintenance, cleaning & repair, noisy air pumps at hot tubs, noisy water pumps at the hot tub or spa, and other hot tub, spa or whirlpool bath diagnosis & repair topics.

Spa Heater Troubleshooting & Repairs

Here is a 20+ year old Heat Wave II electric heater for a spa or hot tub showing the main controls. Newer digital heater units will have similar features.

• The Pump ON/OFF switch is the main power switch for this system. Nothing will work when this switch is in the OFF position.
  
  Watch out: Do not turn on the pump before preparing the hot tub / spa according to the manufacturer's directions or you may damage the unit.
  
  See SPA / HOT TUB PUMP OPERATION
  
  Watch out: missing from this hot tub installation is a separate, GFCI - protected emergency - off switch readily accessible to building occupants or tub users.
• The Heat Level switch 
  
  adjusts the temperature to which the heater will warm the spa / hot tub water. As shown the switch is set to its highest position.
• The "Blower Switch" and "Pump Switch" connections 
  
  in the lower area of the photo are individually connected by plastic air tube to push-buttons located on the rim of the spa or hot tub (shown earlier in this article). By using pneumatic controls (air) to operate the actual electrical switch inside the Heater Control and Pump Control the risk of electric shock is reduced substantially.

Below are two more key features of most hot tub or whirlpool tub heaters:

1. Spa heater on light
   
    (green arrow) indicating that the spa heating elements are working and
2. Spa heater thermal overload reset button
   
    / switch (blue arrow). If the spa heating elements are OFF try pressing the heater overload reset switch through the rubber button (that's to keep you from getting fried).

Watch out: do not keep pressing the reset-switch repeatedly. If the system keeps switching off, find and fix the problem. Otherwise the system maybe unsafe.

Watch out: GFCI (Ground fault circuit interrupter) protection should be provided on all hot tub, spa, and pool electrical circuits to reduce the chances of fatal electrical shock.

Troubleshoot a Spa or Hot Tub Heater That's Not Working Properly

If your hot tub or spa heater is not heating at all check that it has electrical power, and check that its indicator light is on [Green arrow in our photo just below].

The Heat Wave II hot tub / spa heater shown above was produced by

• Hot Water Products, 5542 Research Drive, Huntington Beach CA 92649, USA, Tel: 714-891-5509

Most spa heaters will include a thermal overload reset switch [Blue arrow in our photo above]. To protect the spa heater or hot tub heating elements from damage from overheating, this switch will turn OFF the heater if its internal temperatures become too high. A common cause of excessive temperatures in the spa heater and thus of its constant tripping of the thermal overload switch is inadequate water flow through the unit.

For the hot tub heater shown here, Heat Wave notes in the unit's instructions (you kept those, right?) these important points about water pressure and heater operation:

1. Required water flow rate: The filter must be kept clean enough to keep water flow rate (provided by the spa pump) above15 gallons per minute (GPM). If system pressure drops below this level the pressure switch will drop out (turn off) and the hot tub heater will turn off or become inoperative. Incidentally for this heater unit the maximum flow rate in GPM is 60.
   
   Basically, anything that slows the water flow rate may prevent the heater from staying on: clogged piping, clogged filter or strainer, a valve that's closed, a damaged pump impeller, excessive air in the system from air leaks on the suction lines, etc.
2. Required operating system water pressure: A pressure sensing switch inside the heater unit is set to 2 psi. If water pressure falls below this limit the heater will turn off. If your heater is located below the level of the spa this switch may require adjustment for proper heater operation.
3. Maximum heater output water temperature: a high limit thermostat is set to 140°F.
   
   Watch out: Keep in mind that in a spa or hot tub the maximum safe water temperature is 104°F - much cooler.
   Also see this article on SCALD PROTECTION at plumbing fixtures.

Watch out: in returning the hot tub to operation and to keep the heater working for the hot tub illustrated in this article we needed to run the pump at high speed. But before the pump would operate successfully at high speed we needed to take several steps:

Above: when we first turned on the spa pump this Hayward filter leaked like mad. The white deposits all over it indicated a history of leaks when the unit was last used. We removed the filter cap and found that it was cracked.

1. Fill the hot tub or spa above the jets.
   
   Until you put enough water into the spa to reach above the jets you cannot operate the pump - you won't know if the spa or its piping or fixtures are leaking or not. Unfortunately when you find leaks you'll probably have to drain the spa below the level of any parts to be removed or repaired.
2. Fix leaks anywhere in the system.
   
   At the filter, leaks due to cracks in the filter top were squirting water everywhere. It may be possible to repair cracks and small leaks at the filter using epoxy, taking care not to obstruct air bleeder holes and threads for the filter air bleed screw. Otherwise such parts need to be replaced.
3. Clean the spa filter: if the spa filter is clogged the pump may not reach the required flow rate to operate the spa heater.
   
   Hayward filters can be removed and washed with warm water and a garden hose with spray attachment. Don't try a car wash high-pressure sprayer or you'll ruin the filter. If the filter or its sealing gaskets are torn or damaged, replace it.
4. Fill the spa or hot tub to its upper water intake level. If the water level is below the upper pump intake port air will be drawn in to the port, the pump will cavitate,
   
   it will be very noisy, and it will not pump water properly. In turn this may keep the spa heater from operating. See the photo just below.

Above: required water level in the hot tub or spa: must be over the upper spa water intake port that in this installation is hidden behind the vertical plastic cover. Otherwise at high speed the spa pump will draw air, cavitate, and fail to pump properly. When cavitating or pumping air, the pump will also be as noisy as all get-out.

Inside the Whirlpool Heater Control Box

Below: a peek below the top cover of this whirlpool tub heater control shows us several key components:

Whirlpool Tub Heater Trips Thermal Overload & Water Won't Get Hot Enough

At the time of our inspection (March 2016) this whirlpool tub would not heat satisfactorily, shutting its heater off by tripping the thermal overload switch at about 95°F.

Earlier we noted that inadequate water flow rate can trip the pressure switch causing the tub to fail to heat. The pressure switch is there to prevent burn-up of the heater element - a condition that would occur if the heater were switched on and the pump was not circulating water or if there was no water or not enough water in the tub.

On this whirlpool tub the temperature control and sensor are sold as a unit and the device has been replaced at least once before: below is an old temperature control and sensor found under the tub.

On this whirlpool tub heater unit we suspect that the temperature sensor or its relay is the problem.

While our repair service tech opined that the system is beyond economical repair, if we can swap in a new temperature sensor for $50. or less in parts (and free labor from the author) this repair might be worth trying.

As we learned with heating boiler aquastats (AQUASTAT TROUBLESHOOTING), something as simple as poor thermal contact between the temperature sensor bulb and the sides of the well into which it inserts can be enough to cause thermostatic controls to malfunction.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

How to fix a hot tub that's too hot

I have a hot tub heated by a stainless steel heat exchanger.

On the tub side I have a 4 hp pump for the jets and a fractional hp pump for heat and filter. Either pump circulates thru heat exchanger and filter. Small pump only circulates on timer for filtering or Tstat for call for temp.

Call for temp also opens a zone valve with end switch that pulls a relay to fire the home heating system gas boiler and start the main heating system circulating pump. The zone valve for the tub is on the return side of the piping. I have had constant problems maintaining temp (always too hot) and am looking for recommendation for improvement.

Should I install another zone valve on the supply to the heat exchanger?

Should I be using domestic hot water heater instead of directly off boiler?

Is it possible the zone valve is stuck open and circulating hot water thru heat exchanger on call from any other zone? On 2018-04-26 by Don Hoolihan

by (mod) -

If your hot tub is too hot then I suspect that the controlling thermostat is improperly-set or is not the right model to provide the necessary temperature.

by Don

The thermostat is the first thing I checked. It is working properly. The stat pulls a relay which turns on the fractional hp pump and opens the zone valve at the boiler. Zone valve end switch makes and pulls another relay which turns on whole house circulating pump and fires the boiler.

The water from the boiler is less than 200 since that is what the limit is set to.

The 1" pex supply line to the heat exchanger is about 50' away from the zone valve, however the valve is on the return side and I would think there would not be any hot water to the heat exchanger if not calling for heat, however, the supply side at the heat exchanger is usually very hot.

Could it be the water temp is so hot and the rate of rise, temp, is faster acting than the thermostat? You said not the right model. I bought it thru a pool/jacuzzi supply house. I have tried two models to no avail.

by (mod) - thermostat seems to respond too slowly to temperature changes

I'd be surprised that the thermostat would not act "fast enough" it the thermostat is actually working at all and assuming it's properly located.

I'd also check that you're not circulating boiler water through the heat exchanger involuntarily, such as can happen if there is a defective zone valve or check valve that doesn't close when it should.

Reset button not working on hot tub control panel

I tried to press the high limit reset button it wasn’t going in so I took the button off the red one put a small screwdriver in there it killed the light on there but it didn’t kill the power because I hooked A tester and it’s still getting power

but I looked in there in a little Control panel it looks like behind the button or below it a spring is broke thank You will you help me On 2020-02-29 by Russell

by (mod) -

Russell the reset button is a replaceable part - a switch - matched by the manufacturer of the specific control being repaired, but

Watch out: for shock hazards and other damage: I think I also see signs of water leaks and corrosion inside the assembly.

by Russel

Where can I get the whole assembly?

By mod: from the manufacturer, from any local electrical or hot tub supplier and from some online vendors such as Grainger.com

Jacuzzi DC25 leaking water under the rapid heater

My whirlpool jacuzzi bath model #DC25 Was leaking water under the rapid heater while filling tub. Once I turned pump on it stopped leaking . What causes this ? On 2018-12-11 by Lee

The water is coming up through the rivets on a electrical component on the inside heater itself . Only leaks while filling the tub once motor is on the leak stops .I know crazy ! On 2019-01-14 by Lee

by (mod) -

I don't know, Lee, perhaps a change in water pressure adjusted a gasket, or a vibration slightly changed a connection that was leaking. Or there was water siphoning out of a vent.

Watch out: I would be very nervous about water inside of an electrical component or motor - as there could be risk of fatal shock hazards. Leave the system OFF until it has been repaired.

We need to know what that component is and probably to replace it. My WILD GUESS is it may be a temperature or pressure sensor.

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Continue reading  at SPA, HOT TUB, SWIMMING POOL INSPECTION & CODES, or if your spa or hot tub needs repair see SPA HOT TUB WHIRLPOOL REPAIRS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• SCALD PROTECTION

• STEAM BATH / SHOWER GENERATOR INSTALLATION

• HOT TUB SPA WHIRLPOOL OPERATION & REPAIR

  • SPA TURN ON PROCEDURE
  • SPA CONTROLS & SWITCHES
  • SPA / HOT TUB BLOWER UNIT
  • SPA / HOT TUB FILTER CLEANING
  • SPA / HOT TUB FILTER LEAK REPAIR
  • SPA / HOT TUB FILTER REPLACEMENT
  • SPA / HOT TUB HEATER REPAIR
  • SPA, HOT TUB, SWIMMING POOL INSPECTION & CODES
  • SPAS, WHIRLPOOLS, INSTALLATION
  • SPA / HOT TUB JET CLOG REPAIR
  • SPA / HOT TUB LEAKS
  • SPA / HOT TUB & POOL OZONE
  • SPA / HOT TUB PUMP OPERATION
  • SPA / HOT TUB PUMP REPAIR
  • SPA JETTED TUBS NOISE
  • SPA HOT TUB WHIRLPOOL REPAIRS
  • SPA / HOT TUB CHEMICALS & CHLORINATION
  • SPA / HOT TUB DRAIN / WINTERIZING PROCEDURE
  • SPA / HOT TUB / POOL MANUALS, PARTS, REPAIR, SUPPLIES
• SCALD PROTECTION

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SPA / HOT TUB HEATER REPAIR at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BATH & KITCHEN

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