Welcome to the forum.
Bottled water contains water from different areas - some of it is even bottled from tap water!
So unless you know where it comes from, you really don't know what's in it, i.e. fluoride, etc....
I wish you good luck in your research and hope you find what sets off your UC.
Rx meds didn't help me. But 4.5 mg LDN +Paleo diet +supplements=REMISSION.Protein shakes w/almond milk,Maca powder,L-Glutamine,D-Ribose,chia seeds.VSL#3,K2,VIt. D3,slippery elm bark powder.For more info,my protocol is the 11th post at this link: https://www.healingwell.com/community/default.aspx?f=38&m=1666318
If you have any questions, you can find my email address at my profile.