BoilerFaultCodesYour boiler is displaying an information code because the pump that moves water around your pipes is spinning at a different speed than expected.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Pump speed actual value
What causes this fault?
This code occurs when the boiler's main control board detects that the internal pump is spinning faster or slower than the speed it has been commanded to reach. It is usually caused by air bubbles trapped in the system or a build-up of debris like sludge that is physically slowing the pump's rotation. In some cases, it can also happen if the electrical signal between the pump and the main control board becomes inconsistent.
This issue is more common in autumn when heating systems are turned back on after summer, as settled debris or air pockets can migrate into the pump.
DIY fix possible
Check that all radiator valves are fully openEnsure there is enough water pressure in the system (check the gauge)Restart the boiler to see if the advisory code clears
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like D.15 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.