BoilerFaultCodesYour boiler is struggling to detect a rise in water pressure when the pump starts up, which is preventing it from firing for your heating or hot water.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Fault: Pump/water shortage - Insufficient pressure jump detected when starting the pump
What causes this fault?
This fault occurs when the boiler's internal computer fails to see a small spike in water pressure that should happen the moment the pump begins to spin. The most common reason is that the pressure sensor has become blocked with sludge or debris, though it can also be caused by a failing pump or air trapped within the system. Essentially, the boiler won't fire because it cannot confirm that water is actually moving through the heat exchanger.
This fault is slightly more common in autumn when heating systems are switched back on after a summer of inactivity, as pumps can seize or sludge can settle during the warmer months.
DIY fix possible
Check the pressure gauge and ensure it is between 1.0 and 1.5 barTop up the system pressure using the filling loop if it is too lowReset the boiler after increasing the pressure
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