Skip to content
TapBuff
ZIP

Mountain Ridge

What EPA’s and Washington’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
28 people
Connections
21
Water source
Groundwater
Based in
Roslyn, WA
County
Kittitas
Owner
Private
Hardness
Soft

The short answer

1 result is above EPA’s legal limit, and 2 more are above the health goal. The worst: Total trihalomethanes (TTHM), above the legal limit. 1 health-based violation since 2016.

What handles it

What was found

Lead and copper: EPA SDWIS monitoring periods ending 2024 to 2025.

Total trihalomethanes (TTHM), arsenic, haloacetic acids (HAA5), fluoride, nitrate and chromium (total): Washington’s own results, samples taken from Dec. 10, 2024 to May 29, 2026.

Above the legal limit1

Total trihalomethanes (TTHM)

Forms or is added in treatment

Above the legal limit

220ppb

Highest yearly average, 2024 to 2026

2026 average: 23.6 ppb

Averaged by year, the highest was 220 ppb, in 2024, about 2.8 times EPA’s legal limit of 80 ppb. In 2026, the latest year on file, its three samples averaged 23.6 ppb. EPA recorded a violation for total trihalomethanes (TTHM) at this utility in 2025.

What handles it

  • NSF/ANSI 53 look for “Trihalomethanes (TTHM) Reduction”
  • NSF/ANSI 58 look for “Trihalomethanes (TTHM) Reduction”

Above the health goal2

Arsenic

Comes from the source

Above the health goal

4.0ppb

Highest yearly average, 2024 to 2025

2025, one sample: 4.0 ppb

Averaged by year, the highest was 4.0 ppb, in 2024: below EPA’s legal limit of 10 ppb, but above its health goal of zero. In 2025, the latest year on file, its one sample was 4.0 ppb.

What handles it

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

Lead

Comes from pipes, often your own

Above the health goal

3.5ppb

90th percentile, 2025

In the latest period, 9 in 10 homes sampled were at or below 3.5 ppb, below EPA’s action level of 15 ppb. The action level drops to 10 ppb on Nov. 1, 2027. EPA’s health goal for lead is zero.

What handles it

Below EPA’s limits3

Haloacetic acids (HAA5)

Forms or is added in treatment

Below EPA’s limits

59.5ppb

Highest yearly average, 2024 to 2026

2026 average: 0.36 ppb

Averaged by year, the highest was 59.5 ppb, in 2024, below EPA’s legal limit of 60 ppb. In 2026, the latest year on file, its three samples averaged 0.36 ppb.

What handles it

No certification claim covers this compound yet.

Fluoride

Forms or is added in treatment

Below EPA’s limits

0.8ppm

Highest yearly average, 2024 to 2025

Averaged by year, the highest was 0.8 ppm, in 2025, below EPA’s legal limit of 4.0 ppm. Its highest single sample was 0.81 ppm. That was also the latest year on file.

What handles it

Nitrate

Comes from the source

Below EPA’s limits

1.7ppm

Highest sample; found in 2 of 4

2026, one sample: 1.0 ppm

The highest sample, in 2025, was 1.7 ppm, below EPA’s legal limit of 10 ppm. In 2026, the latest year on file, its one sample was 1.0 ppm.

What handles it

  • NSF/ANSI 58 look for “Nitrate/Nitrite Reduction”
  • NSF/ANSI 53 look for “Nitrate/Nitrite (30 ppm challenge)”
One compound tested and not foundBelow the reporting level in every sample. Not found is not the same as zero.
  • Chromium (total)

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: Trihalomethanes (TTHM) Reduction, Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction

    For: Total trihalomethanes (TTHM), Arsenic, Lead

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

  • NSF/ANSI 58

    Claims: Trihalomethanes (TTHM) Reduction, Arsenic (Pentavalent)<=50 ppb Reduction, Lead Reduction

    For: Total trihalomethanes (TTHM), Arsenic, Lead

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

At the tap, or for the whole house?

Lead and copper usually come from pipes and fixtures inside or near your home. A whole-house system sits where water enters, so it cannot catch what your own plumbing adds after it. For those, the filter that counts is the one at the tap. 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

The best water filters for lead, ranked

Hardness

Soft, 11 mg/L (0.6 grains per gallon), at its one sampling point, 2024 to 2025.

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 0.6 grains per gallon, salt includedSoftener or salt-free conditioner?Washington water hardness, utility by utility

Violations since 2016

Contaminant or ruleTypePeriodMeasuredStatus
TTHMThe running average was above the legal limit.EPA: Maximum Contaminant Level Violation, AverageJuly 1, 2025 to Sept. 30, 2025126 UG/LArchived
Health-based violations only. Resolved and archived mean the utility returned to compliance or the state closed the record. 1 monitoring or reporting violation not shown.

What this report can’t tell you

  • Everything else. Total trihalomethanes (TTHM), arsenic, haloacetic acids (HAA5), fluoride, nitrate and chromium (total) results here are Washington’s own from 2024 on, with EPA’s national file for 2012 to 2019. Mountain Ridge’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; Washington’s results run from Dec. 10, 2024 to May 29, 2026.

Testing your own tap

Mountain Ridge’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 Washington certifies.

No lab Washington certifies is within 75 miles of the area Mountain Ridge serves on the state’s list. Some take samples by mail; the state’s page lists them all.

All 84 certified labs for Washington

Sources

PWSID WA53AB326. Rebuilt from EPA data on Oct. 18, 2026.

Also in Kittitas County

All Washington utilities

What to do next