This technique for heating a bath is not safe and therefore I do not recommend you try this yourself.
I featured this device in a video a while ago. It was made to provide a hot deep bath in an old flat with an inadequate water heating system. The unit relies on the resistivity of the clean water to limit current leakage. It does potentially make the water live at mains voltage in a manner that couples current very well to human bodies. I did consider grounding the frame, but the difficulty arose in properly sealing the ends of the elements which are not designed to be submerged and potentially get quite hot.
It looks nice in operation and will slowly heat a full bath to any temperature desired. (but not too high!)
The element I used is a 240V 2kW kettle element. The circuit is protected by an RCD/GFCI for "safety". I measured the leakage to ground at just 1 or 2mA.
