Issaquah, WA water hardness

Tap water hardness
41mg/L
2.4gpg
Soft

Reported by Bellevue City of · September 2025

WA typical
36 mg/L
EPA health violations since 2016
0
Data
Utility report

Tap water in Issaquah has about 41 mg/L of hardness, which is 2.4 grains per gallon. On the USGS scale that counts as soft. The number comes from Bellevue City of, dated September 2025.

Issaquah on the hardness scale, with nearby cities
060120180240300360+WA typical 36Newcastle: 27 mg/LNewcastle 27East Renton Highlands: 30 mg/LEast Renton Highlands 30Bellevue: 34 mg/LBellevue 34Bryn Mawr-Skyway: 35 mg/LBryn Mawr-Skyway 35Mercer Island: 39 mg/LMercer Island 39Snoqualmie: 41 mg/LSnoqualmie 41Renton: 49 mg/LRenton 49Union Hill-Novelty Hill: 50 mg/LUnion Hill-Novelty Hill 50Fairwood: 53 mg/LFairwood 53Sammamish: 62 mg/LSammamish 62Issaquah 41mg/L as calcium carbonate060120180240300360+WA 36Newcastle: 27 mg/LNewcastle 27East Renton Highlands: 30 mg/LEast Rento. 30Bellevue: 34 mg/LBellevue 34Renton: 49 mg/LRenton 49Fairwood: 53 mg/LFairwood 53Sammamish: 62 mg/LSammamish 6241 mg/Lmg/L as calcium carbonate
Soft 0–60 mg/LModerately hard 61–120 mg/LHard 121–180 mg/LVery hard 181+ mg/L

Issaquah sits close to the typical Washington figure of 36 mg/L. Of the 10 nearest cities we track, 5 have softer water and 4 have harder. The range nearby runs from 27 mg/L in Newcastle to 62 in Sammamish.

What 41 mg/L means at home

Soap and shampoo lather with very little product. Kettles and showerheads stay mostly free of white crust.

Some people notice that soap feels slow to rinse off in soft water. That slippery feel is normal and harmless.

Hardness is not a health problem, and EPA sets no limit for it. It is a matter of scale and soap.

What to do about it

Nothing, as far as hardness goes. At 41 mg/L a softener would have almost nothing to remove.

Carbon filter

If the water tastes of chlorine, a pitcher or faucet carbon filter takes care of that. It does not change hardness.

EPA record for Issaquah's water system

Issaquah Water System · PWSID WA5336350

No health-based violations since 2016

Serves about 43,584 people from surface water.

Health-based
0
Monitoring or reporting
0
Open now
0

EPA lists Issaquah Water System as the system serving Issaquah. The hardness figure above comes from a different system's report, which TapWaterData uses for Issaquah.

Health-based means a contaminant above its legal limit or a missed treatment step. Monitoring and reporting violations are late or missing tests and notices. Source: EPA ECHO, 2026Q3 export, violations with periods starting 2016 or later. Full EPA record.

Questions

Is Issaquah water hard?

No. It measures about 41 mg/L (2.4 grains per gallon), which the USGS classes as soft.

What is the water hardness in Issaquah in grains per gallon?

About 2.4 gpg. One grain per gallon equals 17.1 mg/L, so 41 mg/L divided by 17.1 gives 2.4.

Has the Issaquah water system had EPA violations?

EPA records show no health-based violations for Issaquah Water System since 2016.

Nearby cities

All 145 cities in Washington

Hardness data: TapWaterData US Water Hardness (utility report, September 22, 2025), CC BY 4.0. Population: US Census Bureau. Violations: EPA ECHO. How we use them.