Approximately 40 million people in the US are served by private wells, many of which are untreated. The investigators estimate that 1.29 million cases of gastrointestinal illness (GI) per year are attributed to consuming water from untreated private wells in the US. These cases of GI can cause a significant burden in terms of health care costs and lost work/school days, as well as increased risk to developing longer term health complications. This impact is magnified when accounting for vulnerable populations such as children under the age of 5, the elderly and the immunocompromised. The investigators are preparing to conduct the first household randomized controlled trial (RCT) to investigate whether consuming well water treated by ultraviolet light (UV) compared to consuming untreated private well water decreases the incidence of self-reported gastrointestinal illness and respiratory infections in children under 5. The investigators will collect illness symptom data using a combination of weekly text messages and online illness questionnaires.

Inclusion Criteria:

• Child resides in Berks, Bucks, Chester, Lancaster, Lehigh, or Montgomery County in Pennsylvania
• Household is served by a private well
• Participant child is under the age of 5 (under 4 at time of enrollment), who is a full-time resident of the home and drinks untreated well water (75% or more of water consumption must be from untreated well water)
• Parent/guardian has access to a phone with texting capabilities

Exclusion Criteria:

• Child participant is immunocompromised
• Child participant has a chronic gastrointestinal condition
• Child takes daily oral steroids
• Household treats water before consumption (with the exception of water softeners)