UK trade guideShower Spares 4 min readUpdated 11 July 2026

How to Replace the Flow Cartridge on a Grohe Grohtherm 1000 Cosmo (UK)

UK guide to swapping the flow cartridge in a Grohe Grohtherm 1000 Cosmo shower valve. TMV2 compliance, part numbers, tools.

Grohe

The part

Fit a new flow-control cartridge on the Grohe Grohtherm 1000 Cosmo to fix stiff or leaking on/off — usually a 1/4-turn ceramic disc.

Isolate

Close the built-in isolators on the Grohe Grohtherm 1000 Cosmo valve body — accessed through the escutcheon plate.

Swap the flow cartridge

Some Grohe 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 Grohe Grohtherm 1000 Cosmo 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 Grohe 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 Grohe?
For TMV2/TMV3 compliance always fit genuine Grohe cartridges. Aftermarket voids the Grohtherm 1000 Cosmo approval.
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