Potterton E85901 Fault Code

What causes the Potterton E85901 fault?

This fault occurs when the safety system detects an issue with the cold water entering your boiler's internal storage tank. It is usually caused by a failure of the inlet control valve, which manages the pressure of the incoming mains water to prevent the system from over-pressurising. If this valve becomes blocked or fails mechanically, the boiler shuts down the hot water production to prevent damage.