Why is My Hot Tub Not Heating Up?

As cool air sweeps in and temperatures drop, nothing’s quite as invigorating as sinking yourself neck-deep into the warm waters of your hot tub. You’re expecting a wave of tropical paradise to warm your bones. So imagine your surprise when you dip your toes into what feels like an ice pond instead!

There’s only one thing that’s more “invigorating” than a hot tub in cold weather, and that’s a paradoxically cold hot tub in cold weather. Even though winter lows are particularly high in South Florida, a hot tub that’s not heating up can be an absolute nuisance. While it can be quite confusing, the good news is that it’s usually a pretty easy problem to diagnose.

Before we begin, we should remind you to NEVER work on a broken hot tub while it’s plugged in. doing so could put you at risk of electrocution. ALWAYS make sure that your hot tub is turned off, the circuit breaker is shut off, and the unit is disconnected from all power sources. Better yet, leave it to a professional!

Reason #1: Dirty Filters and/or Broken Flow Switches

They don’t make ‘em like they used to — cars, ovens, houses, and hot tubs, too! Most modern hot tubs are equipped with a computer that monitors and regulates the water flow and temperature. 

One component of that computer is a flow switch or pressure switch that tells the hot tub whether to turn on or off. When there isn’t enough water flowing past this switch, or if the hot tub’s water pressure is too low, this switch automatically shuts off your hot tub. This helps increase the lifespan of the hot tub’s heater because it reduces the amount of time the heater “runs dry,” or is powered on without actually heating any water. 

So, if your hot tub isn’t heating, it may be because the water flow is too low and the flow switch is shutting off the power. This could be caused by a number of problems, including: 

• Dirty or clogged filters
• Low water level
• Broken flow switch

If a dirty filter is causing your hot tub to lose flow, a rinse or replacement should do the trick. And while it’s easy to diagnose, it’s more difficult to “do-it-yourself” and repair a broken flow switch. Since modern hot tubs are generally run by a computer, it’s best to have a professional come look at it and replace any needed parts.

Reason #2: Broken Thermostat or Temperature Sensor

Most modern hot tub thermostats are connected to the hot tub’s motherboard, and sometimes these parts are faulty. The sensor may be installed improperly, the wire may be frayed and experiencing a faulty connection, or something else may be wrong. The good news is that these parts are generally inexpensive, about $100 or less, and easy to replace.

Reason #3: Broken Heating Element

Given enough time, even water corrodes everything, including a hot tub heating element. Yes, your hot tub water should be balanced at a slightly alkaline pH of 7.2–7.8. But even a slight change in acidity could corrode the heating unit. In this case, you may need a professional to install a new heating unit, and you might also want to take a look at your water chemistry.

Reason #4: It’s Not Turned On

We know, we know … you came here for a solution only to have someone ask you, “Is it turned on?” We understand this isn’t a tech support call, but your hot tub’s computer will likely also be connected to a high limit switch, which automatically shuts off the hot tub if the water gets too hot, about 110–120º Fahrenheit.

If the high limit switch keeps tripping, it may be a sign of a broken switch, calcium buildup, or something else. This is also a job best left to a professional.

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If something about your hot tub isn’t letting it heat up quite right, or if it continues to trip the circuit breaker, we can help! Just give us a call or request a service appointment.