How to Replace an Expansion Relief Valve (UK)
Fit a new 6 bar expansion relief valve on Megaflo, Santon and OSO unvented cylinders. G3 notifiable.
MegafloSantonOSO
Function
The ERV opens at 6 bar to protect the cylinder from over-pressure. Constant weep = valve seat scaled or set-pressure too low.
Fit
Isolate cold. Depressurise hot side by opening upstairs tap. Undo old ERV (15 mm compression on discharge). Fit new with copper washer. Test by opening cold slowly and observing pressure gauge stops below 6 bar.
Frequently asked questions
- Do I need G3 for this?
- Yes — expansion controls on unvented systems are G3-notifiable.
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