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Capitol Water Corp water quality report, rewritten

Serves
9,000
Connections
2,811
Water source
Groundwater
Based in
Boise, ID
County
Ada
Owner
Private
The ZIP code it serves

83704

PWSID ID4010022 · EPA data

Read this first

  • PFNA (above the health goal) was found in four of 8 samples, highest 51 ppt. Above the 10 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.
  • PFOS (above the health goal) was found in four of 8 samples, highest 9.8 ppt. Above the 4.0 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.
  • PFOA (above the health goal) was found in two of 8 samples, highest 5.9 ppt. Above the 4.0 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.
  • Lithium (above EPA’s health benchmark) was found in eight of 8 samples, highest 24 ppb. Above EPA’s health reference level of 10 ppb, a screening level rather than an enforceable limit.

3 health-based violations since 2016. Details are below.

What handles it

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 June 9, 2023 to Oct. 8, 2024. Each blue tick on a scale is one sample where it was found.

NSF’s PFAS claims are tested to below 20 ppt. EPA’s limit is 10 ppt, and EPA says no certification yet shows a filter reaching its levels.

PFNA (above the health goal)

Comes from the source

51 (above the legal limit in at least one sample)ppt

Highest of 8 samples; found in four

Above the 10 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.

What handles it

PFOS (above the health goal)

Comes from the source

9.8 (above the legal limit in at least one sample)ppt

Highest of 8 samples; found in four

Above the 4.0 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.

What handles it

PFOA (above the health goal)

Comes from the source

5.9 (above the legal limit in at least one sample)ppt

Highest of 8 samples; found in two

Above the 4.0 ppt legal limit in at least one sample. Compliance is judged on a running annual average, not one sample.

What handles it

24ppb

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.

PFHxS

Comes from the source

5.5ppt

Highest of 8 samples; found in five

Detected, below the legal limit and the health goal.

What handles it

PFBS

Comes from the source

4.0ppt

Highest of 8 samples; found in two

Below EPA’s hazard index benchmark of 2,000 ppt. PFBS has no legal limit or health goal of its own.

What handles it

Also found, with no federal limit

EPA measured these PFAS to learn how often they occur. None has a legal limit or a health goal yet.

CompoundHighest sampleFound inCertification claim
PFPeA5.4 ppt2 of 8None covers it
PFHxA5.2 ppt2 of 8None covers it

Tested and not found

Below EPA’s minimum reporting level in every sample taken from June 9, 2023 to Oct. 8, 2024. Not found means not measured above that level, which is not the same as zero.

All 23 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
  • PFDA
  • PFDoA
  • PFEESA
  • PFHpA
  • PFHpS
  • PFMBA
  • PFMPA
  • PFPeS
  • PFTA
  • PFTrDA
  • PFUnA

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageApril 1, 2025 to June 30, 202531 UG/LArchived
Combined UraniumThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJan. 1, 2025 to March 31, 202531 UG/LArchived
Lead and Copper Rule RevisionsThe required inventory of lead service lines was not completed or submitted on time.EPA: LSL InventoryOct. 17, 2024—Resolved
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 123 monitoring or reporting violations not shown.

What handles it

A certification covers specific claims, not a whole standard. Look for these claims on the certifier’s listing, not the box. Wording varies a little: NSF writes “Lead Reduction,” WQA just “Lead.”

  • NSF/ANSI 53

    Claims: Total PFAS Reduction, PFOS Reduction, PFOA Reduction

    Other certifiers’ wording: Perfluorononanoic Acid (PFNA); Perfluorooctane Sulfonate (PFOS); Perfluorooctanoic Acid (PFOA)

    For: PFNA, PFOS, PFOA

  • NSF/ANSI 58

    Claims: Perfluorooctane Sulfonate (PFOS), Perfluorooctanoic Acid (PFOA)

    For: PFOS, PFOA

At the tap, or for the whole house?

These come with the water itself, so a whole-house system certified for the same claims treats every tap and shower. A filter at the tap treats drinking water for much less. How whole-house systems compare.

Compare five-year costs

Filters with those claims on a certifier’s listing

TapBuff earns a commission if you buy through some links on this page. It does not change which standard or filter we name. As an Amazon Associate, TapBuff earns from qualifying purchases. How TapBuff makes money

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 Capitol Water Corp’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 June 9, 2023 to Oct. 8, 2024.

Other Idaho utilities

All Idaho utilities

Sources

What to do next

  • Read up on the 4 marked results

    What each one does to health, where it comes from, and the certification claim that addresses it.

    Start with PFNA

  • Get the utility’s own report

    Capitol Water Corp must send you a water quality report every year. It lists nitrate, arsenic and byproduct levels this page cannot.

    How to read it

  • Test 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 do

  • Compare certified filters

    What the filters certified for these results cost over five years, cartridges included.

    Compare five-year costs