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Inflatable hot tub heater not working: causes and fixes

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In short

Most heater problems on inflatable tubs come from low water flow, usually a dirty or missing filter, or from settings: the heater switched off, the set temperature below the water temperature, a timer or the bubbles pausing it. Check those first. If the water still will not heat, or an error code shows, follow the manual and contact the maker.

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Few things are more frustrating than lifting the cover expecting warm water and finding it cold. On an inflatable tub, the heater sits in the pump unit and only works when water flows through it properly and the controls tell it to run. That means most heater problems have simple causes you can check yourself in a few minutes. This guide takes you through the checks in order, from the most common to the least, and explains when the fault is likely to be in the pump and it is time to contact the maker.

Check 1: water flow and the filter

The heater needs a steady flow of water. A dirty or clogged filter, a filter fitted wrongly, low water or an airlock in the hoses can all stop it. Many pumps show a flow error, such as E02 on many Lay-Z-Spa pumps, but some just stop heating.

Turn the pump off, take out the filter, rinse it with a hose and refit it, or try a new one. Check that the water is up to the fill line and that the inlet and outlet are not blocked. Restart and see whether the heater light comes on.

  1. 1

    Switch off and unplug the pump.

  2. 2

    Remove and rinse the filter, or fit a new one.

  3. 3

    Check the water level is at the fill line.

  4. 4

    Check the hoses and connectors are fitted firmly and not kinked.

  5. 5

    Plug in, switch on and turn the heater on.

Check 2: settings, timers and locks

It sounds obvious, but the heater button may simply be off, or the target temperature may be at or below the current water temperature. On many pumps the heater light shows red or green to tell you whether it is heating or holding. A panel lock can stop buttons working until you unlock it.

Timers and power saving modes can also stop heating at certain times. App controlled tubs may have a schedule set in the app. Check every timer, and on some models note that the heater pauses while the bubbles run. Your manual explains the lights and modes for your pump.

Check 3: weather and air temperature

In cold weather, the heater may run but lose the battle against heat escaping through the walls and cover. Makers often state a lowest air temperature for heating; below it the water may barely warm or the tub may show a low temperature code. Freeze protection modes may run the heater only to stop the water freezing, not to heat it fully.

Fit the cover tightly, add a ground mat and shelter the tub from wind. Our winter guide lists tubs with better insulation and freeze protection.

01020304004812162024hours on a 2.2 kW heater°C600 L: about 9 h1,000 L: about 15 h1,000 L, cover off (slower)
Minimum heating from 10 °C to 38 °C on 2.2 kW. With the cover off, heat is lost and the climb is slower.

Check 4: heater is on but heating is slow

A 2 kW heater adds only around 1 to 2 °C an hour in good conditions. If you have just filled the tub with cold water, it may take a day to reach temperature. Use the heat-up calculator to see the minimum time for your litres. Scale on the heater can also slow it down in hard water areas; see hard water and limescale.

When it is likely a pump fault

If the filter is clean, flow is good, settings are right and the weather is mild, but the heater light never comes on or the water stays cold, the heater element, thermostat or control board may have failed. An error code that comes back after a reset also points that way. Codes differ between pump models, so look them up in your manual. See Lay-Z-Spa error codes for common ones.

Note the code, the model and when the fault started, then contact the maker or seller. Many pumps are covered by a warranty for a set period.

Note:Do not open the pump unit or try to repair the heater yourself. It contains mains electrics close to water. If the RCD trips or water gets into the pump, stop using the tub and contact the maker or a qualified electrician.

Quick reference

Working through the table in order solves most cases without a call to the maker.

SymptomFirst check
Heater light offHeater button, panel lock, timers
Flow error codeFilter, water level, hoses
Light on but water coldSet temperature, cover, air temperature
Very slow heatingLitres, cold tap water, filter and scale
Code returns after resetManual, then the maker
Heater not working: symptom and first check

Frequently asked questions

Why is my Lay-Z-Spa heater not working with no error code? Check the heater button, the set temperature, any timer and the filter. Some pumps stop heating without showing a code.

Can a dirty filter stop the heater? Yes. Low flow stops many heaters as a safety measure. Rinse or replace the filter.

Why does the heater stop when the bubbles are on? On many 13 A tubs the heater pauses so the total load stays within the plug's limit.

Is it safe to keep resetting the pump? If a fault keeps coming back, stop and contact the maker rather than resetting it repeatedly.

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