Water Quality in Seattle, WA

Seattle's water quality is good overall. Hardness is low at 20 PPM, and no contaminants exceed health guidelines. Most homes here do not need a water softener.

Seattle Public Utilities · Source: Cedar River + Tolt River · Serves 737,015 residents

20
Hardness (PPM)
35
TDS (PPM)
1
Chlorine (mg/L)
2
PFAS (ppt)
2
Lead (ppb)
20 PPM 0 400 Soft
CONTAMINANT LEVELS Hardness 20 PPM TDS 35 PPM PFAS 2 ppt Lead 2 ppb Chlorine 1 mg/L Nitrate 0.5 mg/L

Hardness Scale: Where Seattle Falls

Soft 060120180250400+
Minimal — very clean source waterLight chlorine treatment

What Seattle's Water Means for Your Home

Seattle's water is soft at 20 PPM. At this level, hard water is not a significant concern for most households. Scale buildup is minimal, and a water softener would provide little measurable benefit. If you are considering water treatment in Seattle, focus on contaminant filtration rather than softening.

Beyond hardness, Seattle's water quality is generally within EPA guidelines for regulated contaminants. Chlorine is present at 1 mg/L as a disinfectant residual, which is normal for municipal water systems. If you notice a pool-like taste or experience dry skin, a whole-house carbon filter is the most common and affordable solution. For homeowners who want to understand the full picture, requesting your utility's annual Consumer Confidence Report provides neighborhood-level data.

ContaminantDetectedHealth GuidelineLegal LimitStatus
Hardness (as CaCO₃)20 PPM< 60 PPMNo federal limit✓ OK
Total Dissolved Solids35 PPM< 300 PPM500 PPM✓ OK
PFAS (total)2 ppt4 ppt (EPA)4 ppt (2024)✓ OK
Lead2 ppb0 ppb (no safe level)15 ppb (action level)✓ Low
Chlorine / Chloramine1 mg/LTaste threshold ~1.04.0 mg/L✓ Normal
Nitrate0.5 mg/L5 mg/L10 mg/L✓ OK

Good news for ${esc(c.city)} residents. Your water quality is generally good. Most homes in this area do not need a water softener. If you have concerns about lead (especially in buildings constructed before 1986) or chlorine taste, a point-of-use filter is the most practical and cost-effective solution.

About Seattle's Water Supply

Water Utility: Seattle Public Utilities

Water Source: Cedar River + Tolt River

Population Served: 737,015

Hardness: 20 PPM (undefined grains per gallon)

Water quality can vary by neighborhood and season. The values above represent typical averages reported by Seattle Public Utilities. To get exact numbers for your address, request a copy of the most recent Consumer Confidence Report (CCR) from your utility, or have your water independently tested.

Compare Seattle to Other Washington Cities

Spokane

104 PPM · Moderately Hard

Tacoma

21 PPM · Slightly Hard

Vancouver

13 PPM · Soft

Bellevue

26 PPM · Slightly Hard

Kent

16 PPM · Soft

Everett

26 PPM · Slightly Hard

Frequently Asked Questions About Seattle Water

Is Seattle tap water safe to drink?
Seattle's water meets EPA legal standards for drinking water safety. However, legal limits and health-optimal levels are different things. Review the contaminant table above for specific numbers and how they compare to both legal limits and health guidelines.
Do I need a water softener in Seattle?
No. At 20 PPM, Seattle's water is very soft. A water softener would provide no benefit here. Focus on filtration if you have specific contaminant concerns.
What water filter is best for Seattle?
The best filter depends on which contaminants you want to address. See our softener vs. filter guide to understand the difference between these categories.
Where does Seattle's water come from?
Seattle's drinking water is sourced from Cedar River + Tolt River and treated by Seattle Public Utilities.
What is the hardness of Seattle water in grains per gallon?
Seattle's water hardness is undefined grains per gallon (GPG), which equals 20 parts per million (PPM). This is classified as soft. To convert: 1 GPG = 17.1 PPM.
Does Seattle water damage tankless water heaters?
At undefined GPG, Seattle's water is unlikely to cause significant issues for tankless water heaters. However, if you notice reduced flow or efficiency over time, scale buildup could be a factor. Annual flushing with vinegar is good maintenance regardless of hardness.
Is Seattle water safe for babies and infants?
Seattle's water meets all EPA safety standards and is generally considered safe for preparing infant formula. The hardness minerals (calcium and magnesium) are not harmful. If your home has older plumbing, running cold water for 30 seconds before use is a good precaution to flush any lead from pipes.

Data sources. Water quality data compiled from EPA SDWIS, EWG Tap Water Database, USGS water hardness studies, and the Seattle Public Utilities Consumer Confidence Report. Hardness and contaminant levels represent typical average values and may vary by neighborhood and season. Last updated: 2026-02-12.