Johnston Municipal Water Supply water quality report, rewritten
- Serves
- 24,897
- Connections
- 7,657
- Water source
- Surface water bought from another system
- Based in
- Johnston, IA
- County
- Polk
- Owner
- Local government
PWSID IA7740011 · EPA data
Read this first
- Lithium (above EPA’s health benchmark) was found in eight of 8 samples, highest 33 ppb. Above EPA’s health reference level of 10 ppb, a screening level rather than an enforceable limit.
No health-based violations on file since 2016.
What was found
Highlighted: above the health goal, or EPA’s health benchmark where there is no goal. Circled: above the legal limit in at least one sample, or the action level. Every scale puts that line at its middle.
PFAS and lithium: EPA UCMR 5, samples taken from Jan. 6, 2025 to Oct. 7, 2025. Each blue tick on a scale is one sample where it was found.
Lithium (above EPA’s health benchmark)
Comes from the source
33ppb
Highest of 8 samples; found in eight
Above EPA’s health reference level of 10 ppb, a screening level rather than an enforceable limit.
What handles it
No certification claim covers this compound yet.
Tested and not found
Below EPA’s minimum reporting level in every sample taken from Jan. 6, 2025 to Oct. 7, 2025. Not found means not measured above that level, which is not the same as zero.
All 30 compounds tested and not found
- 11Cl-PF3OUdS
- 4:2 FTS
- 6:2 FTS
- 8:2 FTS
- 9Cl-PF3ONS
- ADONA
- HFPO-DA (GenX)
- Lead
- NEtFOSAA
- NFDHA
- NMeFOSAA
- PFBA
- PFBS
- PFDA
- PFDoA
- PFEESA
- PFHpA
- PFHpS
- PFHxA
- PFHxS
- PFMBA
- PFMPA
- PFNA
- PFOA
- PFOS
- PFPeA
- PFPeS
- PFTA
- PFTrDA
- PFUnA
Violations since 2016
No health-based violations on file with EPA since 2016.
What this report cannot tell you
- Levels of everything else. Federal bulk data carries results for PFAS, lithium, lead and copper, and violations for the rest. Nitrate, arsenic, disinfection byproducts and other levels are in Johnston Municipal Water Supply’s own annual report, which it must send you every year.
- Your own plumbing. Lead results are the 90th percentile across homes the utility samples. Your home’s service line, solder and fixtures decide yours. A certified lab test is the only way to know.
- Anything after the latest data. SDWIS data is from 2026 Q2; UCMR 5 samples are from Jan. 6, 2025 to Oct. 7, 2025.
Other Iowa utilities
- Des Moines Water Works246,055
- Iowa - American WTR Co - Davenport147,720
- Cedar Rapids Water Department142,364
- Sioux City Water Supply85,791
- City of Ankeny76,207
- West Des Moines Water Works73,959
- Waterloo Water Works69,504
- Iowa City Water Department68,753
- Council Bluffs Water Works64,447
- Dubuque Water Works59,667
- Ames Water Treatment Plant55,177
- Urbandale Water Utility45,605
Sources
- EPA UCMR 5 occurrence data, file of Aug. 27, 2026
- EPA SDWA bulk download (SDWIS federal data), 2026 Q2
- Limits and goals: each contaminant’s page, with its EPA source.
- How this page is built: methodology.
What to do next
Read up on Lithium
What each one does to health, where it comes from, and the certification claim that addresses it.
About LithiumGet the utility’s own report
Johnston Municipal Water Supply must send you a water quality report every year. It lists nitrate, arsenic and byproduct levels this page cannot.
How to read itTest your own tap for lead
Your service line, solder and fixtures decide the lead at your faucet, not the utility’s average.
Lead in your water: what to doDecide if you want a filter at all
A filter for taste or chlorine is a preference, not a need. The standards say what each kind can do.
NSF/ANSI standards, decoded