Cant test tap water by the batch. Tap adds unwanted elements in small amounts that increase to points thats hard to fix and confuses you by where the source came from.Also could add many unwanted elemts you dont test for. All it takes is a bad water change to cause problems as city water is never consistant.
If you ever have issues then ruling out the water source can make things much easier.Tap can add ammonia , nitrate , phosphate, copper , pesticides , and ect..