Fixing the Water pump not switching off. It was a micro switch on the bathroom basin tap. I first isolated each tap by removing the wires from the switches that are located on the taps, until the pump switched off. removing the bowl to make it easier to removed the switch, and replaced with a new one.The kitchen tap is different, this just applies to the shower and bathroom basin.
Just had the same problem with a van recently collected and not even used yet! There is a pressure valve/switch near the dump valve - which was new to me. It was a matter of backing it off a quarter turn or so till the pump stopped.
May be handy for others with different systems to the OP?
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