Water hardness by state
How hard is the water in Oklahoma?
Tap water in Oklahoma averages 16.6 grains per gallon (284 ppm calcium carbonate). That number determines how fast limescale coats your water heater, shower glass and appliances.
Based on 320 measurements from 30 monitoring sites, 2018-01 → 2023-12.
Water hardness by county in Oklahoma
Medians of the individual measurements recorded in each county. Hardness varies far more within a state than between neighbouring states — this is where your own figure actually comes from.
| County | gpg | mg/L | Range (mg/L) | Classification |
|---|---|---|---|---|
| Oklahoma County | 17 | 290 | 199–475 | Hard water |
| Bryan County | 18.7 | 319 | 267–361 | Hard water |
| Canadian County | 28.8 | 492 | 383–548 | Very hard water |
| Sequoyah County | 2 | 35 | 21–43 | Soft water |
| Marshall County | 22.1 | 378 | 229–506 | Very hard water |
| Pawnee County | 13.7 | 235 | 95–284 | Moderately hard water |
Range shown is the 10th-90th percentile of local measurements. Counties with fewer than five samples are omitted rather than estimated.
What 16.6 gpg means in Oklahoma
This is hard water: visible scale on fixtures within weeks, clogged shower heads, stiff laundry and a water heater working overtime. Anti-scale protection is strongly recommended.
What it does to your home
Water heater: even a thin layer of scale insulates the heating element and drives energy use up.
Appliances: dishwashers, washing machines and coffee makers scale up and fail years early.
Fixtures and skin: white spots on faucets and glass, dry skin and dull hair after every shower.
How this figure was obtained
Median of the site-level medians at 30 ambient monitoring sites in the USGS National Water Information System (320 individual measurements, 2018-01 → 2023-12). Each site is collapsed to one value first so that a heavily sampled location cannot skew the state figure; the range shown is the 10th-90th percentile across sites. This describes the raw water resource, not a specific municipal tap after treatment.
Water Quality Portal — USGS National Water Information System (NWIS), characteristic "Hardness, Ca, Mg"Statewide average — hardness varies by utility and season. Always verify with your local water quality report.
Frequently asked questions — Oklahoma
Is 16.6 gpg considered hard water?
On the US scale, 0–3.5 gpg is soft, 3.5–7 gpg moderately hard, 7–10.5 gpg hard and above 10.5 gpg very hard. At 16.6 gpg (284 ppm), water in Oklahoma is classified as Hard water.
Does Oklahoma have a limescale problem?
Water in Oklahoma averages 16.6 gpg — Hard water. The harder the water, the faster calcium carbonate deposits build up in water heaters, appliances and pipes. Below 3.5 gpg the risk is minimal; above 7 gpg scale becomes a running cost.
How do I find the exact water hardness at my address in Oklahoma?
Check your utility's annual water quality report (Consumer Confidence Report) or your water bill, or use our free interactive hardness map. Hardness can vary widely between neighboring utilities in Oklahoma.
Do I need a salt-based water softener at 16.6 gpg?
Not necessarily. Salt softeners add sodium to your water and need constant refills. LIMPEO treats limescale with an electromagnetic field — no salt, no chemicals, no maintenance — and keeps healthy minerals in your drinking water.