Water in San Marcos comes from groundwater as well as surface water. The groundwater comes from the Edwards Aquifer while the surface water stems from Canyon Lake. In order to comply with federal regulations set forth for drinking water, the surface water must be treated before it can be sent through a tap. The treatment process often leaves contaminants of its own. Additionally, it has been found that all tap water contains some level of contaminants.

In 2014, the City of San Marcos Conducted a water quality study and found that the water meets all of the standards set forth by the EPA for safe drinking water. Contaminants were still found to be present. Some of the contaminants found in San Marcos drinking water included haloacetic acid, barium and nitrate. Many of these contaminants come from the treatment of water in order to make it safe to drink. Aqua Pure home water filtration systems will eliminate 99.9% of these harmful contaminants from your drinking water.