Shingles more likely to be an issue with a particular microbiome profile.

Research indicates that Herpes Zoster is more likely to become active with a particular expression of the gut microbiome being infected with cyanobacteria and tyzerella3.  See here.

Interestingly, Austin, Texas has been found to have a problem with cyanobacteria contaminating its water supply.  See here.  
Other contaminants known to be excessive (see here and here) in the Austin water which are known carcinogens can suppress the immune system and likely promote the activation of viral infections such as Herpes Zoster.  
Bottom line…You can’t be healthy drinking tap water, and you’ll be challenged simply bathing in unfiltered water as well.