Community Water System · PWS CT1410051
Marianapolis Prep School - St Johns
Operator location Thompson, Connecticut - smaller served population (≤ 999) at 128 people served; 424 SDWIS violations on record from groundwater sources.
- 128
- People served (this PWS)
- 424
- EPA violations (this PWS)
- 43
- Health-based (this PWS)
- Untested
- UCMR5 (this PWS)
Marianapolis Prep School - St Johns standing, high SDWIS violation third
128 people served (SDWIS) - smaller served population (≤ 999). Corpus terciles use 29,740 systems serving 500+ (the sitemap cohort). Health-based share 10% is middle-third health share (≤ 23%).
The verdict
Marianapolis Prep School - St Johns sits in the upper third of the sitemap cohort by violation count (424), so the tables below sample a dense compliance trail rather than a near-clean ledger. Population served is smaller (128; smaller served population (≤ 999)), so each violation row represents a compact service footprint. Health-based share is 10% (middle-third health share (≤ 23%)). No UCMR5 PFAS test appears for this system in this extract.
- 424
- Total EPA violations on record
- 10%
- Health-based (MCL / treatment failure)
- 128
- People served by this PWS (SDWIS)
- N/A
- PFAS compounds detected (UCMR5)
Population ordinals match the sitemap cohort (systems serving 500+, population_served DESC). See methodology · corpus placement.
System Details
- System Type
- Community
- Owner Type
- Private
- Connections
- 1
- County
- Windham
- School/Daycare
- No
- MCL Violations
- 42
- Monitoring Violations
- 321
- Treatment Tech Violations
- 1
Violation History
Contaminant violations recorded by EPA.
| Contaminant | Category | Count | Latest |
|---|---|---|---|
| Coliform (TCR) | MR | 53 | 2006 |
| Chlorine | MR | 43 | 2007 |
| Coliform (TCR) | MCL | 42 | 2007 |
| Consumer Confidence Rule | Other | 23 | 2019 |
| Gross Alpha, Excl. Radon and U | MR | 18 | 2006 |
| Combined Radium (-226 and -228) | MR | 18 | 2006 |
| Combined Uranium | MR | 18 | 2006 |
| Public Notice | Other | 7 | 2008 |
| BHC-GAMMA | MR | 4 | 2007 |
| Toxaphene | MR | 4 | 2007 |
| Aldicarb sulfoxide | MR | 4 | 2007 |
| Carbofuran | MR | 4 | 2007 |
| Atrazine | MR | 4 | 2007 |
| LASSO | MR | 4 | 2007 |
| 2,4-D | MR | 4 | 2007 |
| 2,4,5-TP | MR | 4 | 2007 |
| Pentachlorophenol | MR | 4 | 2007 |
| Chlordane | MR | 4 | 2007 |
| Diquat | MR | 4 | 2007 |
| Di(2-ethylhexyl) phthalate | MR | 4 | 2007 |
| Dinoseb | MR | 4 | 2007 |
| HEXACHLOROBENZENE | MR | 4 | 2007 |
| Benzo(a)pyrene | MR | 4 | 2007 |
| Heptachlor | MR | 4 | 2007 |
| ETHYLENE DIBROMIDE | MR | 4 | 2007 |
| 1,2-DIBROMO-3-CHLOROPROPANE | MR | 4 | 2007 |
| Picloram | MR | 4 | 2007 |
| Dalapon | MR | 4 | 2007 |
| Aldicarb | MR | 4 | 2007 |
| OXAMYL | MR | 4 | 2007 |
Violation Count vs. the National Corpus
Marianapolis Prep School - St Johns has 424 recorded EPA violations, 94% of the 29,740 public water systems serving 500+ people nationwide carry fewer, and 6% carry more. 10% of this system's own violations are health-based (43 of 424), and it ranks unranked by population served among that same cohort.
EPA violations vs. the national water-system corpus
Public water systems serving 500+ people (EPA SDWIS)
424 Higher than most more violations than 94% of 29,740 water systems
the national water-system corpus, bucketed by value
Each bar is a band; taller bars hold more water systems. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA SDWIS · 2026-05-15
Population served record for Marianapolis Prep School - St Johns
EPA SDWIS lists 128 people served and 1 connections for this PWS, confirm the service-area footprint on the federal report before comparing to municipal census totals.
Sources: EPA SDWIS
Nationwide peers
424 violations · 128 served: nearest cross-state SDWIS matches.
Cross-state systems with comparable violation load
Nearest cross-state community systems (500+ served) by total SDWIS violations on record.
What to do with Marianapolis Prep School - St Johns
Use this system's EPA-reported record as a starting filter, not a final verdict.
- See how every tracked system in Connecticut compares on the same EPA violation measures. Connecticut systems
- Check whether PFAS was detected at this system under UCMR5 testing. PFAS guide
- Find and compare another public water system by name or PWSID. Search systems
EPA SDWIS and UCMR5 figures are informational only, not a substitute for a certified lab test of your own tap water.