If your hot tub won’t come up to temperature, the natural assumption is that the heater has packed in. Nine times out of ten, in our experience, it hasn’t. Heating problems have a handful of likely causes, and the heater itself is often the least of them. Here’s what’s worth checking yourself before you pick up the phone, and where to stop and call someone in.
What should I check first if my hot tub won’t heat?
- Check the cover. A cover that’s loose, waterlogged or split lets heat pour out, especially overnight or when it’s cold and windy.
- Check the set temperature. Obvious, yes, but a temperature that’s been nudged by accident, or a panel stuck in economy or away mode, is one of the most common fixes there is.
- Check the filter. A clogged filter starves the heater of water flow, and most tubs simply won’t heat if the flow drops too low. That’s a built-in safety cut-off, not a fault.
What are the signs of a genuine hot tub heating fault?
- An error code on the display. Write it down exactly, with the make and model, before you call anyone.
- Water circulating and jets running, but the water staying cold. That points more at the heater or a flow sensor than the pump.
- No circulation at all. That’s more likely the pump or a control fault than the heater.
- The heater tripping the electrics over and over. Stop using the tub and don’t keep resetting it.
What should you never do when a hot tub won’t heat?
Don’t pull off electrical covers or go poking around the heater, pump or control pack unless you’re genuinely qualified to. If the unit keeps tripping the supply, isolate it only if it’s safe to, and leave it off. Resetting and retrying again and again is the electrics trying to tell you something is wrong.
When should I call someone to repair a hot tub that won’t heat?
If you’ve been through the cover, the temperature and the filter and it’s still not heating, get it properly diagnosed instead of guessing on. Swapping out a heater that was fine all along is a common and completely avoidable bill. Have the make, model, any error code and a description of what it’s doing ready when you get in touch.
We handle heating faults, pump problems, control-panel issues and leaks across Cornwall and Devon. Our hot tub repair page explains how the diagnosis works, and keeping up with a regular hot tub service heads off many heating faults before they start.
What does a professional check when a hot tub won’t heat?
We don’t turn up and assume the heater’s dead. We work through the system in order: flow, filtration, sensors, the control pack and the element itself, so the diagnosis is a starting point built on evidence, not a guess we’ve committed to.
What are the most common hot tub heating faults?
A few come up again and again. A tub that heats slowly but does eventually get there is usually a flow or filter issue: the heater’s working, just not efficiently. A tub that never heats at all, while the pump and jets run fine, more often means the heater element or a dead flow or temperature sensor. Intermittent heating, fine one day and cold the next, is the awkward one. It usually comes down to a loose connection or a sensor giving flaky readings, and it nearly always needs someone on site to pin down, not a part thrown at it and hoped for the best.
How does a hot tub heat the water?
It helps to know roughly how the heating works, because it explains why so many “the heater is dead” calls turn out to be something else. Water has to flow past a heating element for the tub to warm up, and a flow or pressure switch has to confirm that water is actually moving before the control will let the heater fire. If the flow drops for any reason, the control often shuts the heater off on purpose to protect it, even though the heater itself is perfectly fine. So a tub that will not heat is frequently a flow problem wearing a heater problem’s clothing.
Why is a hot tub not heating usually a flow problem, not a dead heater?
The usual culprits behind poor flow are simple. A clogged filter is the classic one, and cleaning or replacing it fixes a surprising number of not-heating tubs. A low water level can drop flow enough to stop the heater, and it can also let air into the system. An airlock after a refill, or after any work on the plumbing, can stop water moving until it is cleared. And on some tubs an isolator valve left partly closed after a service will quietly starve the heater. None of these mean the heater has failed, which is why we always check flow before condemning any expensive part. It is worth ruling out the filter and water level yourself before anything else.
How do hard water and scale affect a hot tub heater?
In harder water areas, scale gradually builds up on the heating element, much like it does in a kettle. A scaled element heats less efficiently and has to work harder, which can show up as a tub that is slow to reach temperature or one that trips out on overheating because the heat is not carrying away into the water properly. Good water balance slows scale down, and it is one of the reasons keeping on top of the chemistry protects the equipment as well as the water. If your tub has gradually got slower to heat over a couple of years, scale is one of the things we will look at.
Frequently asked questions
How long should a hot tub take to heat up?
It varies with the model, the starting water temperature and the outside conditions, but many tubs raise the temperature very roughly a degree or two an hour. From a cold fill in winter it can take a good while, which is normal. What is not normal is a tub that used to heat fine suddenly taking far longer, or never reaching temperature at all.
My tub heats up but then the temperature drops. What is going on?
That often points to heat escaping faster than the tub can replace it, which usually means a tired or waterlogged cover, or the tub losing heat somewhere. It can also be a flow or heater issue that only shows under load. Check the cover first, and if that is sound, it is worth having looked at.
The heater keeps tripping the electrics. Can I just keep resetting it?
No. A heater that repeatedly trips the power is telling you something is wrong, and continually resetting it is not safe. Stop using it and get it checked. Electrical faults on a tub are not something to gamble with. If it keeps happening, it usually points to a failing heater element or a fault in the wiring or control, and that is something we can test and put right.
Can a dirty filter really stop the tub heating?
Yes, and it is one of the most common causes we see. A clogged filter restricts the flow the heater needs, and the control shuts the heater down to protect it. Cleaning or replacing the filter is cheap, and it is always worth trying before assuming the worst.
Do you carry parts, or is it a long wait for a repair?
We work on the common brands and keep the usual wearing parts available, so a lot of heating and flow faults can be sorted in a single visit. If a less common part is needed we will tell you honestly what the wait looks like. We cover Cornwall and Devon, from our base near Camborne out to Redruth, Truro and beyond, with Nick and Ryan carrying out the repairs themselves.
Reviewed by the Coastal Hot Tubs and Wellness team.
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