/One building /2 properties /one water supply. How to work out bills?

[Waterwoes]

To actually spilt the water we have been told its an immense job involving digging up busy pedestrians pavement, floor of property so at the moment it's one bill spilt between two.

This can't be uncommon in some building so how do we work out what each property uses and should pay?

@ErrolTheDragon thanks this is same, one building with two types in it.

Been a while since I’ve done this but you used to get a discount on the connection for separation of supply
worth getting a quote it might not be as much as you think
only one of you has to get the new supply ( you ) if you’re on the ground floor it shouldn’t be too much trouble to run a new service out

@whatdoidonowffs thanks, I also think we are on old lead pipes and I believe there was also a scheme for that at one point.