It is all about the unnatural chemicals in tap water combined with the trace remains of the detergents on the water bowl. We all know that cats have a great sense of smell and they are instinctive in their behavior which is rooted in wild cat behavior. The domestic cat’s wild ancestor does not drink tap water! 😎 And they do fine on puddle water.
The experts say we should change the water in the water bowl often and keep it all clean which is fine but we are adding to that sensory barrier of artificial, sterilising chemicals in the water.
It can be a little gross to see your cat go outside and drink from a muddy puddle or even rain water logged in the crevices of a manhole cover which does not look clean but the domestic cat’s instincts come out and they behave like a wild cat.
These drinking instincts are also seen in some domestic cats preferring to drink from a running tap (faucet). This is more accurately reflecting wild cat habitat conditions and also it eliminates any possible trace of detergent on the bowl.
More: Cat avoided parasite in tap water by drinking rainwater but many fell ill

Hi RM. I think you should carry on and give tap water to your cats as before. But I don’t know the story about the new reservoir so I could be wrong. But your cats are probably used to tap water and and the sterilising chemicals in it. Thanks for sharing RM. Hope you and yours are well.
Oh dear, they are changing reservoirs in New York City. Therefore, I am scared to drink the water now The other day I decided that we should be giving the purchased springwater instead of tapwater. A friend of mine had a bad reaction to double filtered water. Therefore, I have taken my time switching the girls over. Perhaps that was not the best idea I ever had.