Surface Water Treatment Rules
What this EPA rule requires, what a violation means for you, and what to do about it.
📜 What This Rule Is
The Surface Water Treatment Rules are a family of EPA regulations, beginning in 1989, that require systems using surface water — or groundwater under the direct influence of surface water — to filter and disinfect it. Their purpose is to reduce illness from pathogens such as Giardia lamblia, Legionella, and Cryptosporidium. Cryptosporidium is a particular concern because it resists chlorine, which is why filtration, not disinfection alone, is central to these rules.
⚙️ What It Requires of Your Water System
Covered systems must filter and disinfect their water (a small number that meet strict watershed and water-quality criteria may disinfect without filtering) and continuously demonstrate that treatment is working. Filtered systems must keep turbidity — the cloudiness that indicates filter performance — at or below strict limits, and must achieve set levels of pathogen removal and inactivation. The Interim Enhanced (1998) and Long Term 1 (2002) rules added a Cryptosporidium Maximum Contaminant Level Goal of zero and a 2-log (99%) removal requirement; the Long Term 2 rule (2006) added further Cryptosporidium treatment at higher-risk systems.
⚠️ What a Violation Means for You
A Surface Water Treatment Rule violation usually means a treatment-technique lapse: turbidity rose above the limit, a required level of disinfection was not documented, or monitoring was missed. Because these rules are the barrier between surface-water pathogens and your tap, a sustained treatment failure can mean reduced protection against organisms like Giardia and Cryptosporidium. A brief turbidity excursion is far less serious than a prolonged one. The violation record shows whether it was a short exceedance or an ongoing failure.
🩺 Health Context
The pathogens these rules target — Giardia, Cryptosporidium, and Legionella — cause gastrointestinal illness with diarrhea, cramps, and vomiting, and can be severe or fatal for people with weakened immune systems. Cryptosporidium caused the 1993 Milwaukee outbreak that sickened an estimated 400,000 people. Filtration and proper disinfection are what keep these organisms out of treated water.
🕑 Rule History
The original Surface Water Treatment Rule was issued in June 1989. The Interim Enhanced Surface Water Treatment Rule (December 1998) covered systems serving 10,000 or more people and set the Cryptosporidium goal of zero; the Long Term 1 rule (January 2002) extended those protections to systems serving fewer than 10,000; and the Long Term 2 rule (January 2006) targeted extra Cryptosporidium treatment at the highest-risk sources.
✅ What You Can Do
For a brief, resolved turbidity or monitoring violation, no personal action is generally needed. If your system reports an ongoing treatment failure or issues a health advisory, follow its guidance, which may include boiling water. People with weakened immune systems who want extra protection against Cryptosporidium can use a filter certified to NSF/ANSI 53 or 58 for cyst removal, or boil their water.
Surface Water Treatment Rules: Frequently Asked Questions
What is the Surface Water Treatment Rules?
The Surface Water Treatment Rules are a family of EPA regulations, beginning in 1989, that require systems using surface water — or groundwater under the direct influence of surface water — to filter and disinfect it. Their purpose is to reduce illness from pathogens such as Giardia lamblia, Legionella, and Cryptosporidium. Cryptosporidium is a particular concern because it resists chlorine, which is why filtration, not disinfection alone, is central to these rules.
What does a Surface Water Treatment violation mean for my drinking water?
A Surface Water Treatment Rule violation usually means a treatment-technique lapse: turbidity rose above the limit, a required level of disinfection was not documented, or monitoring was missed. Because these rules are the barrier between surface-water pathogens and your tap, a sustained treatment failure can mean reduced protection against organisms like Giardia and Cryptosporidium. A brief turbidity excursion is far less serious than a prolonged one. The violation record shows whether it was a short exceedance or an ongoing failure.
What should I do about a Surface Water Treatment violation?
For a brief, resolved turbidity or monitoring violation, no personal action is generally needed. If your system reports an ongoing treatment failure or issues a health advisory, follow its guidance, which may include boiling water. People with weakened immune systems who want extra protection against Cryptosporidium can use a filter certified to NSF/ANSI 53 or 58 for cyst removal, or boil their water.
🔗 Related Rules
💧 Related Contaminants
Check your water system's violation history
Search your ZIP code to see whether your water system has any Surface Water Treatment violations on record, plus an overall safety grade and lead testing results.
Search your ZIP code →Rule descriptions are drawn from the EPA's drinking water regulation pages. Violation records come from the EPA's Safe Drinking Water Information System (SDWIS).