To be shocked that this is legal

[TibetanTerrah]

I had to call a plumber out yesterday and while he was here he checked my immersion tank.

I live in a block of 4 rented flats. It seems we all share the same tank. I laughed dryly and said "how does that work with hot water bills then?" And he said there's no way to track who is using what so the bill is divided between you. If someone happens to be a high user then the others effectively subsidise their bills.

Especially now with cost of living rising, I'm surprised that this can be a "thing" and that they can get away with not telling you when viewing and applying. I've lived here three years but have had periods when I haven't lived here (six months over lockdown when I only popped back to get post etc for example), and I was surprised when my electric bill was the same as usual after that time. Now i know why!

There's nothing I can do, but this week has been really shit already and we're only on Tuesday so this revelation has pissed me off even more than it would normally.

I can well believe this OP.
About 20 odd years ago I rented a room in a shared conversion in London. It was originally a house that had been split into 2 flats, one upstairs, one downstairs. The upstairs flat had never to the knowledge of anyone living there, ever had an electricity bill. This information was passed down from tenants to tenants on the assumption that the downstairs flat paid the whole wack. I don't know if they did though because no one ever asked them.

Where I used to live, it was a conversion and I had the same issue too..
can't believe this wasn't disclosed to you before moving in

I can't see how the hot water tank is hooked up to 4 separate meters.

@Apileofballyhoo

I can't see how the hot water tank is hooked up to 4 separate meters.

or possibly hooked up to 1 and the cost just divided by 4 and then what

added to each meter?
the meter reading company adds it on top of the normal readings.

a communal meter is common -our block has that which covers the lights in the hallways and the cleaners using a hoover. We then get rebillled that as a share of our annual management charge we pay.

A communal meter is common, @burnoutbabe, but OP states it is connected to 4 meters, which is why I and (presumably for the same reason) Apileofballyhoo are questioning it... and who told her that. I have 2 water meters (for inside and outside) and they are shown separately on the bill. She also said she is being charged for it through the electricity supplier, not a building service charge.

If the electricity company is billing her for both her meter and a share of a communal meter, her bill should have 2 separate meter numbers (so that the person being billed can check the reading is correct on each meter). Otherwise, if they just added it onto her reading, her meter reading and the number of units used wouldn't tally up, her bill would be for more kWh than the difference between the 2 meter readings. Unless she is right and the immersion heater is somehow connected to 4 meters. I don't think that is possible with a conventional dial/digital meter though (as they measure the electricity flowing through them where the supply enters the building, they can't identify what appliance is using it after it has left the meter and then charge a different rate for different appliances). Unless OP has some uber smart meter that "talks" to the communal meter but I'm not sure that exists and whose wifi would it use?

I think I would be checking that I am not paying the entire bill myself if I were OP.