We are a Miami brand, and we assumed for a long time that Miami water was simply very hard. Everyone says so. The map says so. The chalky shower door says so. Then we went looking for the actual number and found something more useful than a number: the county softens its water, the county does not publish a hardness figure, and the websites that do publish one disagree by a factor of almost four. That gap is the whole reason this brand ships a test strip.
The Miami-Dade Water and Sewer Department's 2024 Water Quality Report describes the treatment plant by plant. Water from the Alexander Orr, Jr. plant "receives lime treatment to reduce hardness," then is fluoridated, disinfected and filtered. It serves customers south of SW 8 Street to about SW 264 Street. The Hialeah plant treats water "similarly to that from the Alexander Orr, Jr. plant," with air stripping added. The John E. Preston plant, whose source water carries more natural organic material, goes through "a slightly different process called enhanced softening." All three draw from the Biscayne Aquifer and feed one common distribution system across most of the county.
Then there is the part most people never read. The South Dade Water Supply System, five smaller plants serving unincorporated areas south of SW 264 Street, pumps treated aquifer water into its own separate network. The report says that water "is disinfected and stabilized for corrosion control." Softening is not mentioned. If you live in the Redland, Homestead or Florida City areas on county water, you are likely getting water much closer to what the aquifer delivers.
The aquifer itself is the reason any of this matters. The Biscayne Aquifer is porous limestone, and USGS work on it found that 84 percent of well analyses were calcium-bicarbonate type water, which is what you get when rain moves through calcium carbonate rock. Untreated, that is classic hard groundwater. The county's plants exist partly to knock it down.
Lime softening works by raising the pH high enough (around 10) that dissolved calcium precipitates out as calcium carbonate and settles. Pulling magnesium out too requires an even higher pH, above about 10.6, and that step is what the industry calls enhanced softening, the same phrase the county uses for the Preston plant. What the process cannot do is finish the job. Calcium carbonate and magnesium hydroxide both stay slightly soluble, so a residual always remains. Water treatment references put the design target for lime-softened water at about 80 to 120 ppm as calcium carbonate, with a practical floor around 50 to 80 ppm; one widely used industrial handbook tabulates cold lime-soda softening at roughly 81 ppm total hardness. On the USGS scale, 61 to 120 ppm is "moderately hard."
So the main system in Miami most likely lands somewhere in the 70 to 120 ppm neighborhood on a typical day. That is a real improvement over raw limestone water. It is not soft, and it is not the number your hair experiences over a year of daily washing.
Two peer-reviewed studies from the University of Cincinnati explain why moderately hard water still leaves film. Evans, Marsh and Wickett measured calcium and magnesium in hair by ICP spectroscopy and found that the amount of metal hair takes up is driven mainly by the hair's own binding capacity, meaning its condition. Bleached or otherwise damaged hair has more open anionic sites and grabs more. Hardness level "had only a small effect on uptake," and hair "became saturated with notable amounts of water hardness metals even after repeated exposure to soft water." Higher water pH increased uptake, because the protein side chains in hair lose protons and become more negative as alkalinity rises. In the follow-up paper, those metals concentrated in the cuticle layers and produced measurable fibre stiffening in both virgin and bleached hair. Stiff hair is hair that snaps instead of bending, which is the breakage story behind this whole category. A separate electron microscopy study found hard-water-treated hair had a ruffled cuticle surface with higher mineral deposition and slightly reduced thickness versus distilled water.
Put those together and "Miami softens its water" stops being reassuring. A moderately hard supply, months of washes, and any color or heat history on the strand add up to the same coated, dull, conditioner-resistant feel people report in very hard cities. It arrives more slowly. It still arrives.
Hardness is not a regulated contaminant under the Safe Drinking Water Act. The county is required to report lead, disinfection byproducts, bacteria and the rest; it is not required to report hardness, and its consumer report does not. That leaves a vacuum, and the internet fills vacuums.
| Source type | What it says about Miami | Where the number likely comes from |
|---|---|---|
| Softener retailers publishing their own readings | About 6 grains per gallon, roughly 100 ppm | Spot measurements on the treated main system; consistent with lime softening |
| Other softener and filter sites | 10 to 12 grains per gallon, roughly 170 to 205 ppm | Regional South Florida averages, or unsoftened systems blended in |
| National "hardness by city" aggregators | Around 380 ppm, over 22 grains | Raw aquifer or county-wide groundwater data, not the softened tap |
| Miami-Dade Water Quality Report | Describes lime softening at three plants; no hardness value printed | Hardness is not a regulated parameter |
Every one of those sources is describing something real. They are just not describing the same thing, and none of them is describing your bathroom. A house on the South Dade system, a condo on the main system, and a well in the Redland can be twenty minutes apart and sit in three different hardness bands.
A total hardness test strip reads calcium plus magnesium, expressed as calcium carbonate, by color against a printed scale. A common consumer strip resolves 0, 40, 80, 120, 180, 250, 425 and 1,000 ppm in under a minute. That resolution is exactly what you need to place yourself on the four USGS bands and pick a chelating cadence: monthly for moderate, closer to weekly for very hard.
What the strip does not read: iron, copper, manganese or chlorine. If your blonde has gone orange or your dark hair has a reddish cast, the hardness strip can come back moderate and you can still have a metal problem, which is the well water story and a job for a different kind of treatment. And a strip reads the water at that tap on that day. Test the shower, not the kitchen, because that is the water your hair meets, and any in-line filter or softener changes the answer between the two.
The plain version: Miami's main-system water is lime-softened to moderately hard, not very hard, the county does not publish the number, the internet's numbers disagree by nearly four times, and moderately hard water still coats hair over time. Nobody can tell you your hardness from a map. A strip can, in a minute, at your own shower. That is why we put one in every box.
Sources
Miami-Dade Water and Sewer Department. "2024 Water Quality Report" (Consumer Confidence Report), published 2025. Plant-by-plant treatment descriptions for Alexander Orr, Jr., Hialeah, John E. Preston, and the South Dade Water Supply System. https://www.miamidade.gov/water/library/reports/water-quality-2024.pdf. The 2025 report was released April 8, 2026 (miamidade.gov/waterreport).
U.S. Geological Survey. "Quality of Ground Water in the Biscayne Aquifer in Miami-Dade, Broward, and Palm Beach Counties, Florida." Open-File Report 2004-1438, citing Radell and Katz (1991) on the calcium-bicarbonate character of 84 percent of 189 well analyses.
U.S. Geological Survey, Water Science School. "Hardness of Water." Hardness bands: 0 to 60 soft, 61 to 120 moderately hard, 121 to 180 hard, over 180 very hard (mg/L as CaCO3).
Veolia Water Technologies. "Water Handbook, Chapter 7: Precipitation Softening." Residual hardness after cold lime and lime-soda softening; process pH around 10.2 to 10.6; tabulated cold lime-soda effluent of about 81 ppm total hardness.
Mountain Empire Community College, Water/Wastewater Program. "ENV 115, Lesson 14: Lime Softening." Design effluent hardness 80 to 120 mg/L as CaCO3, practical residual 50 to 80 mg/L, and magnesium removal requiring pH at or above 10.6 (enhanced softening).
Evans AO, Marsh JM, Wickett RR. "The uptake of water hardness metals by human hair." Journal of Cosmetic Science 2011;62(4):383-391. PMID 21982353. Uptake driven by hair condition and water pH; hardness level had only a small effect; hair saturated with hardness metals even from soft water.
Evans AO, Marsh JM, Wickett RR. "The structural implications of water hardness metal uptake by human hair." International Journal of Cosmetic Science 2011;33(5):477-482. PMID 21923661. Metals concentrate in the cuticle; fibre stiffening in virgin and bleached hair.
Srinivasan G, Chakravarthy Rangachari S. "Scanning electron microscopy of hair treated in hard water." International Journal of Dermatology 2016;55(6):e344-e346. PMID 26711619. Ruffled cuticle surface and higher mineral deposition after hard water treatment.
Industrial Test Systems. "WaterWorks Total Hardness Test Strips." Color scale 0, 40, 80, 120, 180, 250, 425, 1000 ppm; reads calcium and magnesium.
Third-party Miami hardness figures cited in the table were read on September 9, 2026 from softener and filter retailer pages and a national hardness-by-city aggregator; they are quoted to show the spread, not endorsed as measurements of any specific address.