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Siasconset Water Department

What EPA’s and Massachusetts’s records show in this utility’s water: nitrate, arsenic and other regulated chemicals; lead and copper; and violations since 2016, with the certification that handles each result.

Serves
3,000 people
Connections
863
Water source
Groundwater
Based in
Nantucket, MA
County
Nantucket
Owner
Local government
Hardness
Soft
The ZIP code it serves

02564

The short answer

1 result is above the health goal. The worst: Arsenic, above the health goal. No health-based violations on file since 2016.

What handles it

What was found

Copper: EPA’s file records a utility’s copper only when it exceeds the action level. The last here was 1.5 ppm, for the period ending Dec. 31, 2019. None since is on file, so it is not counted as a current finding.

Arsenic, nitrate, fluoride and chromium (total): Massachusetts’s own results, samples taken from June 16, 2020 to May 12, 2026, with EPA’s 2012 to 2019 file for earlier years.

Above the health goal1

Arsenic

Comes from the source

Above the health goal

1.3ppb

Highest yearly average, 2020 to 2026

2026: not found

Averaged by year, the highest was 1.3 ppb, in 2022: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2026, the latest year on file, it wasn’t found in its one sample. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 1.0 ppb, in 2014.

What handles it

  • NSF/ANSI 58 look for “Arsenic (Pentavalent)<=50 ppb Reduction”
  • NSF/ANSI 53 look for “Arsenic (Pentavalent)<=50 ppb Reduction”

Below EPA’s limits2

Nitrate

Comes from the source

Below EPA’s limits

0.96ppm

Highest sample; found in 12 of 14

2026 average: 0.74 ppm

The highest sample, in 2023, was 0.96 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its two samples averaged 0.74 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest sample of 1.2 ppm, in 2016.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.16ppm

Highest yearly average, 2020 to 2026

2026, one sample: 0.15 ppm

Averaged by year, the highest was 0.16 ppm, in 2020, below EPA’s legal limit of 4.0 ppm. In 2026, the latest year on file, its one sample was 0.15 ppm. Earlier, from 2012 to 2019, EPA’s file shows a highest yearly average of 0.19 ppm, in 2014.

What handles it

2 compounds tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)
  • Lead

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

    Claim: Arsenic (Pentavalent)<=50 ppb Reduction

    For: Arsenic

    Other certifiers’ wording: Arsenic (III) (50 ppb influent level)

  • NSF/ANSI 58

    Claim: Arsenic (Pentavalent)<=50 ppb Reduction

    For: Arsenic

    Other certifiers’ wording: Arsenic (Pentavalent)<=300 ppb Reduction; Arsenic (V) (300 ppb influent level)

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.

Filters with those claims on a certifier’s listing

Disclosure: 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

Compare five-year costs

The best reverse osmosis systems, ranked

Hardness

Soft, typically 47 mg/L (2.7 grains per gallon), across 3 sampling points, 2021 to 2022.

Hardness is calcium and magnesium. EPA sets no limit for it: it shows up as scale on fixtures and in water heaters, and as soap that won’t lather. USGS calls water above 60 mg/L moderately hard, above 120 hard and above 180 very hard.

Softeners compared at 2.7 grains per gallon, salt includedSoftener or salt-free conditioner?Massachusetts water hardness, utility by utility

Violations since 2016

No health-based violations on file with EPA since 2016. There are 33 monitoring or reporting violations: a sample missed, late or not reported.

What this report can’t tell you

  • Everything else. Arsenic, nitrate, fluoride and chromium (total) results here are Massachusetts’s own from 2020 on, with EPA’s national file for 2012 to 2019. Siasconset Water Department’s own annual report, which it must send you every year, has the contaminants this page does not show.

  • 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.

  • What it means for your health. This page reports what the records show and EPA’s limits and goals; it is not medical advice. If you are worried about a health effect, talk to a doctor or your local health department.

  • Anything after the latest data. SDWIS data is from 2026 Q3; UCMR 5 didn’t sample this utility; Massachusetts’s results run from June 16, 2020 to May 12, 2026.

Testing your own tap

Siasconset Water Department’s results are for the water it sends out. What your own service line, solder and fixtures add shows up only in a test of your tap, by a lab Massachusetts certifies.

The 3 labs Massachusetts certifies closest to the area Siasconset Water Department serves, in a straight line. Call first: certification is test by test, and not every lab takes samples from homeowners.

  • Barnstable County Health & Env Dept

    Barnstable, MA · about 35 miles

    Certified for bacteria, nitrate, lead and copper, metals, minerals and other inorganics, organic chemicals, disinfection byproducts, PFAS

    (508) 375-6605

  • Envirotech Laboratories Inc.

    Sandwich, MA · about 41 miles

    Certified for bacteria, nitrate, minerals and other inorganics

    (508) 888-6460

  • Wampanoag Environmental Laboratory

    Aquinnah, MA · about 41 miles

    Certified for bacteria

    (508) 645-2903

All 81 certified labs for Massachusetts

Sources

PWSID MA4197001. Rebuilt from EPA data on Oct. 18, 2026.

Towns it serves

Nearby

All Massachusetts utilities

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