1.5 Medium

Malvern 1.5 Fault Code

Also written as 15 — same fault.

The Malvern 1.5 fault code means: your boiler's internal water pressure is too low, which is preventing it from circulating heat effectively around your home.. It appears on 1 Malvern model in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Bar Vessel Pressure (Vessel Volume 8, 12, 12, 18, 24)
Typical repair cost £80-150 (including labour)

DIY fix possible

Locate the filling loop (usually a silver braided hose with one or two valves) under your boiler.Open the valve(s) slowly to allow mains water to enter the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valve(s) tightly to stop the flow and check that the fault code has cleared.

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Malvern models that show the 1.5 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Malvern 1.5 fault code information on this page is sourced and cross-checked against the official Malvern service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026