Sure, assuming anyone has a desire to pump money into a large comparative study like this. It's an extremely reasonable hypothesis but you also have other fact

Sure, assuming anyone has a desire to pump money into a large comparative study like this. It's an extremely reasonable hypothesis but you also have other factors to deal with (size of city resulting in more wear and tear on infrastructure, other environmental factors that could cause deterioration of pipes, water hard/softness, quality of wastewater processing facilities). Age would likely be a major factor but not the only factor.