UK trade guideShower Spares 4 min readUpdated 11 July 2026

How to Replace the Thermostatic Cartridge on a Aqualisa Optic Q Digital (UK)

UK guide to swapping the thermostatic cartridge in a Aqualisa Optic Q Digital shower valve. TMV2 compliance, part numbers, tools.

Aqualisa

The part

Rebalance a scaling Aqualisa Optic Q Digital by swapping the OEM thermostatic cartridge — restores TMV2 approval and 38 °C set-point.

Isolate

Isolate hot and cold at the built-in EasyFit valves or dedicated isolators. Drop the pressure by opening the outlet fully.

Swap the thermostatic cartridge

Undo the temperature handle grub screw, remove the escutcheon and pull the cartridge with the OEM extraction tool — needle-nose pliers will crack the Aqualisa plastic housing.

Commission

Balance hot and cold to within 0.5 bar. Run the Aqualisa Optic Q Digital at max flow for 3 minutes.

Verify max outlet temperature stays below 46 °C per BS EN 1111 by shutting off cold and reading the outlet.

Frequently asked questions

How do I set the max temp?
After fitting, run cold-only, then set the shroud to 38 °C, then hot. Rotate the stop-ring until 43 °C max is achieved at the outlet.
TMV3 compliance?
The Aqualisa Optic Q Digital cartridge is TMV2 approved out of the box. For TMV3 (healthcare) fit the -HC suffix variant.
OEM or aftermarket for Aqualisa?
For TMV2/TMV3 compliance always fit genuine Aqualisa cartridges. Aftermarket voids the Optic Q Digital approval.
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