@siracusa the ‘immersion’ is indeed a heating element immersed inside a large copper tank that heats the water for the house. It’s typically inside a ‘hot press’ which is a small room or cupboard (closet) specifically for the hot water tank. Heating water in this way is extremely inefficient and costs a fortune in electricity hence the panic of leaving it on for too long. It has become an Irish meme, of sorts.

