Up in the Cairngorms walking or teaching survival for Backcountry Survival I have used the Water-to-Go bottle with all types of water. The filter is really good for on the go. Now I am in South Sudan working on a UN mission I use the bottle on a daily basis. Water is treated but from various sources so for my own peace of mind and safety I decant it in to my bottle and I have had no adverse effects. Having seen where the raw water comes from I am content. A great bit of kit.