BoilerFaultCodesIdeal E16 Fault Code
The Ideal E16 fault code means: your boiler has detected that there is not enough water in the system to operate safely, causing it to shut down temporarily.. It appears on 6 Ideal models in our database.
Technical description: Water pressure switch error (lack of water)
What causes the Ideal E16 fault?
This fault occurs when the internal sensor detects that the system's water pressure has dropped too low for the boiler to operate safely. The most common reason is a slow leak in the pipework or radiators, though it can also happen if you have recently bled your radiators without topping the water back up.
This issue is frequently seen in autumn when homeowners turn their heating back on for the first time, as dormant leaks or air trapped in the system can cause the pressure to dip.
DIY fix possible
Locate the filling loop (the flexible silver hose) underneath your boiler.Slowly open the valve(s) to allow water into the system while watching the pressure gauge.Close the valves tightly once the gauge reaches between 1.0 and 1.5 bar.Press the reset button on the boiler control panel.
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Gas Safe Register →Ideal models that show the E16 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Ideal E16 fault code information on this page is sourced and cross-checked against the official Ideal service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026