An immersion heater is, simply put, a number of elements, usually 3, elements, a screwplug and a IP rated terminal box to protect the connections.
![element](https://heatingcalculators.com/wp-content/uploads/2012/10/element.jpg?w=300)
![screwplug sizes](https://heatingcalculators.com/wp-content/uploads/2013/08/img_07441.jpg?w=300)
![Terminal box](https://heatingcalculators.com/wp-content/uploads/2013/08/img_0435.jpg?w=300)
And, in the best Blue Peter traditions, here’s
one we made earlier…
![Immersion Heater](https://heatingcalculators.com/wp-content/uploads/2013/08/img_0433-1.jpg?w=300)
The heater is then screwed throught the side of the tank using a weld boss…
![weld boss](https://heatingcalculators.com/wp-content/uploads/2013/08/accessories9.jpg)
Mild steel tanks require mild steel weld bosses, and likewise, stainless steel tanks require horribly priced stainless steel weld bosses. I’ll tell you what brass bosses are used for when I find out.