The thread on the hot water show noozle wore out so i had to turn the tap off which is connected to the hot water cylinder while i went out and brought a wrench to use on the worn shower noozle. Since that time my water wont heat. I havnt had hot water in 3 days I dont know why it wont heat back up I turned the tap back on so whats the problem?

Sorry, I cant help you, but I feel your pain. I hate it when I cant get hot water!