My immersion heater tank does not seem to be filling. Getting slow running hot water, tried to drain but only got a third of abucket

This immersion tank heater... is this a tankless coil in a boiler? If so, did you open at least one hot water faucet while draining the tank..

No matter which system you have, in order to drain anything off you will need to open a faucet to do it. Do not open a mixing type of valve (single handle)... preferably a single hot water faucet of a two handle faucet.

Let me know more specifically what kind of heater here... a brand name would help.

MARK

my immersion heater tank does not seem 2 be filling. getting slow running hot water, tried to drain but only got a third of abucket

This is a immersion heater, (see image). I've shown you mine, now you show me yours. Tom