ZIP 98101 Water Hardness
Seattle, Washington · Nearest measurement: Seattle (0.6 km)
Calcium Carbonate (CaCO₃)
Also: 1.2 GPG · 1.2 °dH
Annual extra cost
$50–$150
Water heater efficiency
Minimal impact
Dishwasher rinse aid
Low/off
Shower filter
Optional
Tools for Your Area
Limescale Cost Estimator
Annual cost for Seattle hardness level
Softener ROI Calculator
How long until a softener pays back
Skin & Hair Checker
Eczema and hair damage risk at 21 mg/L
Baby Formula Safety
Is your water safe for infant formula?
Pool Chemical Calculator
Doses for Seattle source water
Check Another ZIP
Look up any US ZIP code
Data note: Hardness is matched to the nearest verified municipal measurement point for the Seattle area. Exact hardness may vary within a ZIP code depending on treatment plant zones. For certified data, request your Consumer Confidence Report (CCR) from your local utility — all US water utilities are required by the EPA to publish this annually.