BoilerFaultCodesYour boiler has lost water pressure or cannot detect enough water to operate safely, causing it to shut down to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Water level control
What causes this fault?
This fault occurs when the system's internal sensors detect that the water pressure has dropped too low for the boiler to operate safely. The most common reasons are a leak somewhere in the pipework or radiators, or an expansion vessel that has lost its air charge and can no longer stabilize the pressure. In some cases, the water pressure sensor itself may have failed or become blocked with system debris.
This issue is more frequent in autumn when the heating is turned back on after a long break, as underlying leaks or pressure drops often become apparent during the first full cycle.
DIY fix possible
Check the pressure gauge on the boiler or pipeworkUse the external filling loop to top up the system pressure to 1.5 barEnsure all radiator valves and system isolation valves are fully openRestart the boiler once the correct pressure is reached
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 18-19 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Remeha Gas 350 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.