mira 10.8kw tripped rcd and then would have o hotwate when switched back on?

re: switch off all power to the shower and locate and disconnect the terminals to the heater element. Use a multimeter set on ohms range and check to see if there is any continuity between either or both of the element ends to earth, if so, your element will have split and will be running at low power using earth path as neutral and the only fix is replacement.
I hope this helps... Pete.
reply: done that but there is three points on the top of the tank one red one brown and two coneccted to blue. now i have 11.3ohms between blue and red and nothing between blue and brown or earth and any... please help can it still be the element.?