Water Hardness in Saint Louis, MO
Missouri · 19 zip codes · 7 matched water systems
City avg (weighted): 120 PPM
Dataset updated March 9, 20267 matched water systems in the city rollupIndividual systems and ZIPs can differ. Methodology
How this city reading is built
This city reading is a weighted rollup across 7 matched water systems and 19 ZIP codes. Citywide readings are useful for comparison, but individual utility zones and ZIPs can differ.
Hardness is a mineral-content reading, not a drinking-water safety rating. Use it for scale, appliance, and softener decisions; check your utility report or test your tap before sizing treatment equipment. See how we calculate local readings.
Water Systems in Saint Louis
These systems are matched to Saint Louis, MO. Citywide readings are useful for comparison, but the system serving a specific address may differ from the city average.
| Water System | Source | Hardness | Pop. Served |
|---|---|---|---|
Mo American St Louis St Charles Counties MO6010716 | surface water | 120 PPM Moderately HardUSGS estimate: 273 PPM | |
St Louis City Pws MO6010715 | surface water | 120 PPM Moderately HardUSGS estimate: 222 PPM | |
Kirkwood Pws MO6010430 | surface water | 120 PPM Moderately HardUSGS estimate: 270 PPM | |
Laurel Acres Mhp MO6048147 | groundwater | 120 PPM Moderately HardUSGS estimate: 222 PPM | |
Paradise Estates Mhp MO6048094 | groundwater | 120 PPM Moderately HardUSGS estimate: 222 PPM |
Zip Codes in Saint Louis, MO
What This Means For You
Recommendations are based on the displayed hardness reading. Confirm your tap reading before sizing or buying treatment equipment.
Moderately Hard Water
Your water is moderately hard. You're likely seeing scale buildup on fixtures, spotty dishes, and may notice dry skin or hair. A water softener or conditioner can help.
Recommended Products
Learn more: Do I Need a Water Softener? | Salt-Based vs Salt-Free | Size Calculator | How to Test Your Water
Know your water hardness?
If you've tested your water or have your utility's CCR report, share your reading to help us improve accuracy for Saint Louis, MO.
Frequently Asked Questions
How hard is the water in Saint Louis, MO?
The citywide weighted average water hardness in Saint Louis, MO is 120 PPM (7 GPG), classified as moderately hard. This is based on 7 matched water systems.
Do I need a water softener in Saint Louis, MO?
With a citywide average hardness of 120 PPM, a water softener is worth considering for homes in Saint Louis. Confirm your tap reading before sizing equipment.
Is hard water in Saint Louis, MO safe to drink?
Water hardness itself is a mineral-content reading, not a drinking-water safety rating. Calcium and magnesium are naturally occurring minerals, but you should check your utility's Consumer Confidence Report for contaminant and compliance information.
How many water systems serve Saint Louis, MO?
Saint Louis, Missouri is served by 7 matched water systems across 19 zip codes.
Learn More About Your Water
Do You Need a Water Softener? (Based on Your Water Hardness)
A data-driven guide to help you decide if a water softener is worth the investment based on your actual water hardness level.
10 min readSalt-Based vs Salt-Free Water Softener: Which Do You Need?
Salt-based softeners remove hardness minerals. Salt-free conditioners prevent scale but don't soften. Here's how to choose based on your water hardness level.
10 min readBest Shower Filters for Hard Water (2026 Reviews)
We tested KDF, Vitamin C, and carbon shower filters for hard water. Here are the filters that actually reduce mineral buildup on hair and skin.
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