BoilerFaultCodes 21 Your boiler has switched itself off because the system water pressure has dropped too low to operate safely.
Your boiler has switched itself off because the system water pressure has dropped too low to operate safely.
What to check first
- Locate the small blue filling tap underneath the boiler.
- Slowly turn the tap to allow water into the system while watching the pressure gauge.
- Close the tap firmly once the needle reaches 1.5 bar.
Parts commonly replaced
- Filling loop tap
- Expansion vessel
- Pressure sensor