Why is my Megaflo cylinder making noise or losing hot water pressure?
Common causes include a waterlogged expansion vessel, scale build-up from hard water, or a faulty pressure relief valve — all fixable by a G3 engineer.
Common Megaflo & Unvented Cylinder Faults
Losing Hot Water Pressure
- Waterlogged expansion vessel (most common cause)
- Scale build-up restricting flow — common with London's hard water
- Faulty pressure reducing valve on the mains feed
Unusual Noises
- Banging or knocking often points to a faulty expansion vessel or air in the system
- Whistling can indicate a partially closed valve or scale restriction
These faults should always be diagnosed by a G3-qualified engineer — never attempt to open or adjust an unvented cylinder yourself, as it operates under pressure. Call RARE on 020 7458 4949 for a diagnostic visit.
Reviewed by RARE Plumbing London Engineering Team — Gas Safe registered engineers serving prime London since 2013.
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