All the bits, about £30 (including an extension cord to get from the house to the van to power it..)

Hole cutting time.. nervous much? yup.

Cut the hole tight, so the immersion heater makes its own thread in the plastic of the tank. I had a flange to screw on the back (like a big nut, but one wider flatter edge) but the tank plastic was so thick I could only get half a turn on it. Hence lots of waterproof silicone.


the view from inside the tank. Only had to use it half a dozen times this year, but it works a treat, and not a drop of water leaked yet...
Just dont forget to put it on a TIMER (3-4 hours or so).. I forgot one night, left it on for about 8 hours, the van was warm through and through and the water was as hot as hot bath water!! toasty!