Having been at a few CG where they have their own water system, I wouldn't drink that water ever. Once you know how CG filters work and how often they are actually changed, you might agree with me. Unfortunately you only get that kind of information if you work/volunteer there.
The best turnaround on water testing is 24 hours and a lot of times longer. That means that if the water is tested bad, you have been using it for that long if not longer.
In one case, the water getting filtered by the system, is water that upriver is from farms where cattle walk and other do other things, into the same river just a little, less than one mile, from the system.
Where the CG has a person working on the system, who then is checking it out when that person in gone at least 2 days a week? Probably another ranger with very little knowledge or time to check it out.
Another case, we let a glass of water sit out over night. Never touched that water again.
At the very least, I would always recommend a filter or buy filtered water at grocery stores. There are reasons you find a lot of these machines in the southwestern states.