What do the British call the immersion water heater in their Kitchens?

Clue English racecourse

( No Uk answers please)

Immersion heater? Are you sure? How do you define 'immersion' in this context? Of 'course', I could be thinking of the wrong venue or could be on the wrong 'track' !

Well Fred for arguments sake we'll define it as "the wall mounted Gas water heater/boiler in the Kitchen" OK?

out of edit time I was going to add 1 descriptive word as a clue...which is (water)Geyser Should be easy to answer now?

BTW It says in the WikiPedia that its an American company (of the Name I want) who produced these from the 1930s So the early models could be imports?