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Hot Tub Not Heating — Brand-by-Brand Fixes

If your inflatable hot tub won't heat up, the cause — and the way it shows itself — depends a lot on the brand. A failed heater on a Lay-Z-Spa or CleverSpa often shows no error code at all, the water just never warms. An Intex PureSpa or MSpa is more likely to flash a temperature code. This page is the symptom-led companion to our error codes by brand hub: find your brand below and see the most common heating faults and the DIY fixes that clear them.

Jump to Your Brand

• Lay-Z-Spa / Bestway — usually a PTC heater, stuck relay or scale; often no error code
• Intex PureSpa — watch for E94/E95 temperature codes
• MSpa — heater/flow faults, sometimes SPL/sensor codes
• CleverSpa — heater element or flow/pressure switch; HL if it shuts down

Lay-Z-Spa / Bestway Not Heating

On a Lay-Z-Spa, a heating fault frequently shows no error code — the heater icon stays on (red), but the temperature simply doesn't climb. The usual suspects:

• Heater not actually engaged: the heater and the bubbles/AirJet function can't run at the same time on most models — the heater pauses while bubbles are on. Turn the bubbles off and let it heat.
• Failed PTC heater element: the metal heater block can fail (often after corrosion from poor water chemistry), giving no heat and sometimes RCD tripping. Replacement element ~£30–60 + fitting.
• Stuck heater relay on the PCB: the relay that switches the element doesn't close — engineer diagnosis.
• Limescale on the element: very common in our hard-water coastal area; run a descale and flush (see our full guide to hard water & limescale).
• Thermal cut-out tripped: do a thermal reset — unplug, hold the thermal-reset button 5 seconds, replug, then heat.

Do this first: full thermal reset (Reset → Test → Reset on the PRCD, hold On/Off 5s, press thermal reset), clean the filter, then run 5–6 hours and check the temperature has moved. Full walkthrough on our hot tub not heating guide.

Intex PureSpa Not Heating

Intex PureSpa units are more likely to tell you via a code:

• E94 (water too low / temp too low): often a flow problem — clean the filter and clear the inlet/outlet grilles.
• E95 (water too hot) / E96 / E98: overheat protection has cut the heater; shade the unit, let the water cool and power-cycle.
• No code, no heat: check the heater is enabled (not just filtration), then suspect the heating element or thermistor.

Full code breakdown on the Intex PureSpa error codes page.

MSpa Not Heating

On an MSpa, heating problems often come back to water flow or the sensor:

• E1 / F1 (water-flow): the most common — clean the filter and the debris screens, the heater won't run without flow.
• SPL / temperature-low: water is below range; let it heat with the lid on, check insulation.
• Heater/relay failure (older HEF codes): on older models a heater or PCB fault stops heating — engineer territory.

See the MSpa error codes guide for both code generations.

CleverSpa Not Heating

Like Lay-Z-Spa, a CleverSpa with a failed heater element shows no error code — it just won't raise the temperature (you should see roughly 1°C per hour when healthy). Key causes:

• Failed 1800W heater element: no heat, sometimes RCD tripping when you switch heat on. ~£30–60 part.
• Faulty water pressure / flow switch: this switch fills with debris and stops sending power to the element — a cheap part worth replacing alongside the element.
• HL error: the unit thinks it's overheating and shuts down — usually a flow restriction (worn impeller/weak pump) or a drifting temperature probe, not always the heater itself.
• Temperature probe/sensor: a faulty probe gives wrong readings and can stop or false-trigger heating; replaceable as a DIY part.

Letter-code detail (FC, HL, SL, SH) on the CleverSpa error codes page.

Why Heating Faults Look So Different Across Brands

Bestway (Lay-Z-Spa) and CleverSpa control packs tend to fail silently — the element or relay dies and the panel shows nothing, so you only notice the water never gets hot. Intex and MSpa lean more on coded temperature and flow protection, so you usually get an E code pointing you in the right direction. That's why the diagnostic order matters: on a "silent" brand, rule out settings, timing and insulation first, then move to element/relay testing; on a "coded" brand, read the code against the brand guide before touching anything.

Common Heating Repair Costs (All Brands)

Indicative costs in the Bournemouth, Poole & Christchurch area:

• Filter cartridge: £8–20 (DIY — restores flow to the heater)
• Descale treatment: £0–15 DIY
• Temperature sensor / probe: £15–40 + labour
• Heater element (PTC / 1800W): £30–60 + labour
• Pressure / flow switch: £10–25 + labour
• Control board (PCB): £80–200 + labour
• Typical engineer call-out: £40–80 (often includes first 30 mins labour)

Related Heating & Power Guides

• Hot tub not heating up — the full general guide
• Won't hold temperature — heats then loses it overnight
• Pump not turning on — dead display / no power
• Tripping the electrics — often a heater fault
• Tripping the electrics by brand — the power companion to this page
• Error codes by brand — the code-led companion to this page