UK trade guideControls & Valves 5 min readUpdated 9 July 2026

How to Fit a TMV2 Mixing Valve (UK)

Install a thermostatic mixing valve to protect vulnerable users. TMV2 vs TMV3 approval, sizing and commissioning.

RelianceHoneywellRadaAltecnic

TMV2 vs TMV3

TMV2 = domestic BS 7942 approval. TMV3 = healthcare NHS D 08 approval. Care homes and hospitals must use TMV3.

Fit

Isolate hot and cold. 15 mm or 22 mm compression. Set outlet temperature: 46 °C basin/bidet, 41 °C bath, 38 °C shower. Commission and record.

Frequently asked questions

How often should TMVs be serviced?
Annually — check fail-safe: shut off cold and verify hot flow stops within 5 seconds.
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