City water changing pH!

[Think Green]

I have 3 Zoysia lawns that was tested at the beginning of the season in April with my Kelway pH tester for a general check. The summer was pretty much arid and void of any rainfall for at least 3 months.......a bad drought.
Each lawn is watered regularly by these elderly customers with rotary and horizontal sprinklers. I get my usual call to check the lawns to see if lime is necessary after a season of fertilizers. Often the quick ferts create a more acidic effect on the soils. A couple weeks ago, I do a quick check and the pH is at 8.2 not my reading of 6.5 from back in April. The chemicals placed in city water to protect the pipes and other sterilizing materials is causing this imbalance of alkalinity.
Has anyone else noticed this phenomenon with their readings. I mean, the lawns are all green and healthy looking. I almost purchased lime for the beginning fall application. Instead, It looks like sulfur but not until next spring.
What are some responses from anyone that may have encountered this in their lawns? I mean if the lawns aren't hurting in color why worry but things will get worse.