UK trade guideShower Spares 4 min readUpdated 11 July 2026

How to Replace the Flow Cartridge on a Gainsborough GSE 9.5 electric (UK)

UK guide to swapping the flow cartridge in a Gainsborough GSE 9.5 electric shower valve. TMV2 compliance, part numbers, tools.

Gainsborough

The part

Fit a new flow-control cartridge on the Gainsborough GSE 9.5 electric to fix stiff or leaking on/off — usually a 1/4-turn ceramic disc.

Isolate

Close the built-in isolators on the Gainsborough GSE 9.5 electric valve body — accessed through the escutcheon plate.

Swap the flow cartridge

Some Gainsborough valves use handed cartridges (L/R). Match the flat on the spindle to the handle orientation before refitting.

Commission

Balance hot and cold to within 0.5 bar. Run the Gainsborough GSE 9.5 electric 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

Standard or reversed?
Standard Gainsborough cartridges close clockwise. Reverse handles will require the -R variant.
Any grease?
Silicone grease only — petroleum jelly attacks the EPDM seals.
OEM or aftermarket for Gainsborough?
For TMV2/TMV3 compliance always fit genuine Gainsborough cartridges. Aftermarket voids the GSE 9.5 electric approval.
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