Consider checking with some neighbors to see what their water bill looks like.I'm surprised they back-charged you for previous under billings in October 2024....i thought the bill was just adjusted moving forward. 

Quote from @Blake Alan Quarrie: Has anyone else noticed a significant increase in their Chicago water bill recently?

So I give the bill to my PM and they bill the tenant and they reimburses me.

But to date, I've just set my rents at a rate that accounts for me having to pay the water bill - and informed the residents that each year I'll increase the rent based upon my expenses (including water), so keeping the bill down helps me to help them.But one problem this could cause is if increasing the rent to cover the water bill then places your rent above the market rate.

All this was making bills very high. 

Unfortunately we've had a very cold winter here, with temps holding below freezing for weeks at a time so many of us are seeing high heating bills in general.

I intend on sending the tenant a bill for the exact repair cost as "additional rent" (per the lease) instead of evicting in the winter and deducting from the security deposit.

Is your comparable unit that you get $100 bills for a 4 unit as well?

My suggestion would be to cap your utilities at a certain amount and have Tenants pay anything over that amount.That will help you manage your expenses, and also allow Tenants to gage their usage each month, and make adjustments if they don't want to go over the allotted amount.As far as collection, provide the bill showing any overages and just have them pay for it along with their rent. 

It is common and customary acrossa almost all rentals except some A class office to pay your share of utilities.Now you can make whatever arangment you'd like and work it out however you want with your tenant but if you are going to "share costs" I'd suggest keeping the utilities in your name, and then "back billing" the tenants for that share of their usage, but again thats a lot of work for really no gain in my book.My recommendation would be to simply have the tenants pay all utilities.