How to Diagnose an Unvented Cylinder Fault (UK)
Systematic fault-finding on Megaflo, Santon Premier, OSO and Range Powermax cylinders. G3 compliance.
MegafloSantonOSORangeHeatrae Sadia
Common faults
- Tundish dripping — expansion relief valve, PRV or expansion vessel failed.
- Slow hot water refill — internal PRV blocked.
- Warm cold pipe — one-way check valve failed.
G3 notifiable
Any work on unvented over 15 L requires G3 registration. Discharge pipework, blending valves and expansion controls must all comply.
Frequently asked questions
- How often should an unvented be serviced?
- Annually — inspect expansion, PRV, blending valve, anode (where fitted).
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