A couple of months ago, the immersion heater overheated and melted both the insulation and its plastic cap...
So I assumed the thermostat was faulty, bought and fitted a new one and fabricated a new cap from plastic drainpipe.
The new thermostat has an overtemperature trip, which keeps tripping. So, whatever's wrong is still wrong. I carefully remade all the joints when I replaced the thermostat (I assumed that's what the problem was), so I imagine it can't be that.
Could the element be furred up? We have very hard water and our water softener packed up years ago....