I have read online that tap water from city water systems can change seasonally, so I will start logging this information quarterly and seeing if I can determine that. I will also be checking out my cities water report. For anyone reading, I live in North Worcester, Massachusetts and use the city water system.
My house was built in the 50s and has copper pipes which seem to be in good shape.
For these water quality tests I measure water from the cold line of my water system.