BoilerFaultCodesYour boiler has received a request to provide hot water but is currently unable to complete the cycle, often because it is already cooling down or busy with another task.
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: Hot water requirement error
What causes this fault?
This status occurs when the boiler receives a signal to heat your water but cannot start the burner because it has recently finished a heating cycle and needs to cool down internally. It is often caused by a communication lag between your external timer and the boiler, or a mechanical delay in the internal valve that directs water to your taps. In many cases, it is simply a 'waiting' state rather than a permanent mechanical failure.
DIY fix possible
Check if any hot water taps have been left slightly openTurn the boiler power off and back on again to reset the internal clockEnsure your external timer or thermostat is not stuck in an 'on' position
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 S.20 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Vaillant ecoTEC 65kW is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.