I've just found that our hot water cylinder is weeping from the joint between the body and the top. Since it's over 40 years old (I assume), it's probably simpler to replace than repair. Now, I'm sure there are rules about who can and can't do this, so let's assume that I'm buying one and getting a plumber to fit it, in the same way as I would never do anything electrical or with gas fittings (!).
The house has hot air heating (sadly), which means it's immersion heater only for the DHW. I have no intention of changing this as the house is going onto the market soon and I don't want to start any new major jobs.
Anyway, I've never played with hot tanks before but this is clearly a direct cylinder. Screwfix do what seems to be the best buy (
The real question: Does anyone know if the location of connections (cold in, hot out, immersion heater) is standard? If there's any choice, I'll investigate the market to see what's the easiest fit.
Similarly, is there anything to consider in terms of immersion heater elements? I seem to recall reading that modern cylinders can have two heater bosses and, presumably, this means they can be heated faster. All the elements I can see (eg TLC) are 3kW: Seems to me that 2 x 3kW is too much for the existing 20A supply. Does that mean I have to run another 20A feed or is it reasonable to just cap one boss off? (We've got by for years with one element and I'd rather not have to feed it with a new circuit if I can avoid it.)