andy, may i ask how much liquid is lost during a typical hop boil?
just spent a fun filled evening cleaning the element must look just like yours now, most of the plating missing. had to use more force than i would have liked to remove the corrosion, but its looking a lot better for it.
Around 10-15% per hour, so quite a bit! Plus loss in the boiler when you drain the wort out (absorbed by hops etc). I now collect more wort during sparge than I can fit in the boiler and use this additional wort to top up the boiler near the end of the boil.