The cold water is piped in from your municipality in underground pipes. One pipe goes to the hot water heater for heating and the another stays outside of heater for cold. For drinking water, I filter my water with a Life Straw and/or purchase spring water, determined to be low in NTMs. Cold water from the tap likely has a good number of NTMs due to the various build up in plumbing fixtures. Nonetheless I use this water to rinse my veggies as I usually cook them.