Immersion heater questions

[Deluded]

Seems that the immersion heaters on our tank have packed in (there are two, I dont think one was ever working when we moved in) and so we are stuck with no hot water.

Looking at it (without actually removing it) and at pictures on the interwebery, its just a screw in thing right?

Is it a fairly simple DIY job to fit one of these or am I likely to kill myself? Also, are they generally only one size? I know you can get different length elements but is the screw in part all one size? I havent found anywhere that states otherwise (not for home use anyway).

As far as fitting goes, I assume I turn the water off, empty the tank and go from there? Screw it in etc. I see they have a washer, will it need any sealant? Apart from that, is there anything I should be aware of?

Thanks

ETA - does it really matter what length I get? obviously, I assume, the longer the element, the quicker it heats the water, but I am also assuming, that there wont be anything in the centre of the tank stopping a larger element going in? The tank is atleast 2ft in diameter.

Edited by Deluded on Tuesday 30th June 11:52

[esselte]

I have only ever changed 1. Didn't have to drain the tank completely because the heater screwed into the top..turned power off to the heater,disonnected cable,used a proper immersion heater spanner and undid it,be careful 'cos it looked as though it would be quite easy to deform the copper tank..replace heater(not forgetting the washer..no sealant)reconnect,check for leaks,turn on again..no drama but maybe I was lucky?

[Deluded]

Sounds as I would expect it. Ours has two heaters down the side of the tank so I will need to drain it all out...

Thanks!