Bill, I would imagine that you could go to any bank and ask for savings and interest rates from past years, they should have them
in the records dept. calculate the average usage per mo. per year based on the rates of the water co charges per meter, add in the interest then add a % for overall pain and suffering and inconvenience and you got it....any easier way is to just guess with an estimate..the only thing they can do is challenge it... then you refigure it.....
Tony Rome