BoilerFaultCodesYour boiler has shut down because water intended for your drain is backing up and has triggered a safety sensor.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Condensate pump level switch activated for longer than 3 minutes - boiler locks out.
What causes this fault?
This fault occurs when the internal tank that collects waste water becomes full and cannot empty itself properly. The most common reasons are a mechanical failure of the condensate pump or a blockage in the thin plastic discharge pipe leading away from the boiler. To prevent an internal flood, a safety sensor triggers and shuts the system down until the water level drops.
This fault is particularly common during freezing winter temperatures, as the external portion of the waste pipe can freeze solid and prevent water from leaving the pump.
DIY fix possible
Check if the condensate pump is plugged in and turned on at the wall.Inspect the thin plastic pipe leading from the pump for any kinks or blockages.If the weather is freezing, check if the external waste pipe is frozen and thaw it with warm (not boiling) water.
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 On Off On Off — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Potterton Promax FSB 30HE 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.