Quick answer
Your dishwasher has a fault — usually a failing heating element or pump motor. Stop using it and have it checked by an appliance engineer.
Dishwashers, like washing machines, use both electricity and water — making them prone to earth leakage faults when components begin to fail. The most common cause is a failing heating element that has allowed moisture to penetrate its insulation. If your dishwasher trips the RCD, stop using it immediately. If it only trips during the wash cycle or when heating, the element is the most likely cause. Have an appliance engineer test and repair it — do not continue using a dishwasher that is tripping your electrics.
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