My question involves real estate located in the State of: California

I purchased a house which is technically now classified as a condo, because the lot was split many years ago and another house was built behind mine. The house shares a water line with house behind it, however the houses are not separately metered for water use and myself and the owners of the other property split the water bill 50/50. I looked at the CCRs for the unincorporated "Condo" association and there is language saying each owner has the right to separately meter their own water line, otherwise the houses will split the cost.

As of now a couple with two infants are living in the other house (they are renters) and I am the only person living in my house (which I own). Given the fact the mother is home all day taking care of the babies and there are more people living in that house, it is safe to assume that they are using much more water than me. I am assuming that the owners are including water as part of their tenant's rent and therefore profiting off of me as I am almost undoubtedly paying for some of the other tenant's water. I tried emailing the owners of the other property to request paying (1/3) of the water bill (which is probably still more than I should have to pay) , but they refused to agree to it.

When I talked Dev to services for the City, the engineer said I cannot do a water meter split because of the configuration and would have to install a separate water line which could cost about $6000.

Given all this, do I have legal grounds to force the owner of the other property to split the cost of a new water line? As I mentioned, I would think it is illegal for the other owner to provide his tenants water which I am essentially paying for.

Please let me know what i can do, this gets under my skin everyday as I wake up to water gushing through pipes that I am essentially paying for.