Kissimmee and the surrounding Osceola County communities receive drinking water from Toho Water Authority, which draws entirely from the Floridan Aquifer and applies no softening treatment before distribution. The Floridan Aquifer in Osceola County is a limestone formation, and water moving through limestone dissolves calcium carbonate and magnesium carbonate, producing hard water. USGS National Water Information System (NWIS) data from Osceola County Floridan Aquifer monitoring wells shows calcium concentrations of 28 to 33 mg/L and magnesium concentrations of 5.6 to 6.2 mg/L, calculating to a total hardness range of approximately 95 to 106 mg/L as CaCO3 (5.6 to 6.2 grains per gallon). Toho's 2025 Consumer Confidence Report confirms the Floridan Aquifer as its sole water source, documents that treatment consists only of aeration and free chlorine disinfection, and reports sodium levels of 5.8 to 9.9 mg/L, which is consistent with unsoftened groundwater. Hardness is not a regulated primary contaminant under the Safe Drinking Water Act, so utilities are not required to report it in their CCR. For a complete picture of your home's water hardness, a free in-home test is the only way to get a measurement at your specific tap.
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Who supplies Kissimmee's drinking water
Toho Water Authority is the public water system serving Kissimmee, St. Cloud, Celebration, Intercession City, Buenaventura Lakes, and most of the populated areas of Osceola County. The utility operates under Florida Department of Environmental Protection oversight and is required to publish an annual Consumer Confidence Report (CCR) covering the previous calendar year by July 1 of each year.
Toho's service area is organized into multiple pressure zones and distribution systems. The Eastern Water System (Public Water System ID 349-0751) serves Kissimmee proper and the communities of Buenaventura Lakes, Lake Ajay Estates, and Springlake Village. All Toho systems draw from the same source: the Upper Floridan Aquifer beneath Osceola County.
Toho's 2025 CCR states directly that "underneath Osceola County lies one of the largest pristine reservoirs of fresh groundwater in the country, the Floridan Aquifer. Water from this aquifer is of consistently high quality and is used as the source of potable water for Toho's water system... needs little or no treatment other than aeration to remove hydrogen sulfide (rotten egg odor) and disinfection." Source: Toho Water Authority 2025 Consumer Confidence Report (PDF).
Treatment limited to aeration and disinfection means the mineral content of the Floridan Aquifer passes directly to finished water with no dilution, blending, or softening. Whatever hardness the aquifer carries is what comes out of your tap.
Why Toho's CCR does not list hardness
Most Kissimmee homeowners looking for their water's hardness will pull up the Toho Consumer Confidence Report and find no hardness number listed. This is not an omission by Toho. Hardness is not classified as a primary health contaminant under the federal Safe Drinking Water Act (SDWA), so the EPA does not require public water systems to monitor or report it in their annual CCR.
Hardness causes real problems for plumbing and appliances, but the regulatory framework for drinking water is built around health-based contaminants, and the minerals responsible for hardness (calcium and magnesium from dissolved limestone) are not considered harmful at normal drinking water concentrations. As a result, hardness data for Toho's service area is not available from the CCR.
To find hardness data for the Floridan Aquifer in Osceola County, we turned to the USGS National Water Information System, which archives historical groundwater chemistry samples from monitoring wells across Florida.
USGS aquifer data: Osceola County Floridan Aquifer hardness measurements
The USGS Water Quality Portal (waterqualitydata.us) archives water chemistry data collected from monitoring wells across the United States, including the Floridan Aquifer in Osceola County. We queried USGS NWIS for groundwater sites in Osceola County (FIPS 12097) that had discrete water chemistry sampling data, identified monitoring well USGS-275609081132001 (Joe Overstreet Well, OSF-4, near St. Cloud), and retrieved dissolved calcium, dissolved magnesium, non-carbonate hardness, and total dissolved solids measurements.
The table below shows the raw USGS measurements and calculated total hardness derived from the calcium and magnesium values using the standard formula: hardness as CaCO3 (mg/L) = (calcium mg/L x 2.497) + (magnesium mg/L x 4.116). This formula is from Standard Methods for the Examination of Water and Wastewater (APHA/AWWA/WEF).
| Sample Date | Calcium (mg/L) | Magnesium (mg/L) | Calculated Hardness (mg/L CaCO3) | Calculated Hardness (GPG) | Non-carbonate Hardness |
|---|---|---|---|---|---|
| 1978-12-06 | 28.0 | 6.20 | 95.4 | 5.6 | 0.0 mg/L |
| 1979-03-21 | 32.0 | 6.10 | 105.0 | 6.1 | 0.0 mg/L |
| 1979-05-25 | 33.0 | 5.60 | 105.5 | 6.2 | 0.0 mg/L |
| 1979-09-12 | 30.0 | 5.70 | 98.4 | 5.8 | 0.0 mg/L |
Source: USGS NWIS Water Quality Portal, waterqualitydata.us. Site ID: USGS-275609081132001 (Joe Overstreet Well, OSF-4), Osceola County Floridan Aquifer monitoring well. View monitoring location on USGS.
Key findings from the data:
The non-carbonate hardness measurement is 0.0 mg/L CaCO3 for all four samples. This means every unit of hardness in this Osceola County aquifer water is carbonate hardness, the direct product of calcium carbonate and magnesium carbonate dissolved from the surrounding limestone. There is no sulfate or chloride hardness component. This is consistent with the Floridan Aquifer's limestone geology and the absence of significant industrial mineral inputs.
The calculated total hardness falls in the range of 95 to 106 mg/L as CaCO3, which converts to 5.6 to 6.2 grains per gallon. Using the Water Quality Association's hardness classification scale (soft: 0 to 3.5 GPG; moderately hard: 3.5 to 7 GPG; hard: 7 to 10.5 GPG; very hard: above 10.5 GPG), these measurements fall in the moderately hard to lower hard range. Source: Water Quality Association (WQA).
What the Toho CCR confirms independently
The 2025 Toho Water Authority CCR provides two independent data points that support the USGS hardness range.
First, Toho reports that treatment consists only of aeration and free chlorine disinfection. No ion exchange softening, no reverse osmosis blending, and no chemical precipitation are mentioned. An unsoftened Floridan Aquifer supply will have finished water hardness closely tracking aquifer hardness.
Second, Toho reports sodium concentrations of 5.8 to 9.9 mg/L. Ion exchange water softening converts calcium and magnesium to sodium: each grain per gallon of hardness removed introduces approximately 7.4 mg/L of sodium into the treated water. At 5.8 to 9.9 mg/L total sodium (which includes natural sodium from the aquifer), there is no room for ion exchange softening to be occurring. This confirms the CCR's treatment description: Toho delivers unsoftened Floridan Aquifer water to Kissimmee homes.
Toho also reports disinfection byproducts in the CCR. For the Eastern Water System in 2025: total trihalomethanes (TTHM) had a locational running annual average of 45.9 parts per billion (range 22.9 to 59.1 ppb, MCL 80 ppb), and haloacetic acids (HAA5) had a locational running annual average of 29.3 ppb (range 10.4 to 46.2 ppb, MCL 60 ppb). These are within EPA limits. Toho uses free chlorine as its disinfectant in every system except Harmony, which reports chloramines.
Method note: data sources searched and what we found
We searched three sources for Kissimmee-area water hardness data.
Toho Water Authority CCRs: We retrieved the 2025 Central Water System CCR PDF directly from the Toho Water Authority website. Hardness is not listed anywhere in the report, because it is not required under the SDWA regulatory framework for primary contaminants.
USGS NWIS Water Quality Portal: We queried the Water Quality Portal for all USGS groundwater monitoring sites in Osceola County (FIPS code 12097) with discrete water chemistry data. We identified 17 unique sites. Most are in the rural south portion of the county (Yeehaw Junction area, Kenansville area). We selected site USGS-275609081132001 because it is the only Osceola County Floridan Aquifer monitoring well with dissolved calcium and dissolved magnesium measurements in the NWIS database. The four available samples are from 1978 to 1979. No more recent water chemistry data was found for Osceola County Floridan Aquifer monitoring wells in the NWIS archive.
Geographic note: The Joe Overstreet Well (OSF-4) is located in the southern portion of Osceola County (approximately 30 miles south of Kissimmee proper). The Floridan Aquifer's mineral content can vary across the county. These measurements are the best available USGS data for Osceola County but may not exactly represent the hardness at Toho's production wellfields that serve Kissimmee directly. For the exact hardness at your address, a physical water test is the definitive method.
What moderately hard water means for a Kissimmee home
The USGS data for the Osceola County Floridan Aquifer shows hardness in the moderately hard range, 5.6 to 6.2 GPG. Even at this level, mineral accumulation affects home plumbing and appliances in measurable ways.
Water heaters are the most sensitive appliance. Scale accumulates on heating elements and internal surfaces regardless of whether hardness is 5 GPG or 15 GPG; the rate is lower at 5 GPG than at 15 GPG, but it still occurs. Tankless water heater manufacturers, including Rinnai, Navien, and Noritz, specify maximum inlet water hardness in their warranty documentation because scale is the leading cause of early failure in tankless systems.
Dishwashers and washing machines also accumulate scale over time, and the effectiveness of soaps and detergents is reduced in hard water, requiring more product to achieve equivalent results.
For homeowners in Kissimmee who want to know exactly where their water falls on the hardness scale, a measured test at their specific tap is more reliable than any county or aquifer average. Wellfield location, seasonal aquifer fluctuations, and distribution system factors can all shift the hardness value at a given address. A water softener in Kissimmee FL sized for your home's actual hardness will perform better and last longer than one sized to a general county estimate.
For a comparison of reported hardness ranges across Central Florida utilities including OUC, Toho, and Orange County Utilities, see our Central Florida water hardness by utility reference dataset.
St. Cloud's public water system, the City of St. Cloud Water System, is also operated by Toho Water Authority, which covers it in a separate St. Cloud water quality report. For a dedicated breakdown of the St. Cloud water supply, see St. Cloud, FL water quality and hardness data.
Getting your home's actual water hardness reading
The only reliable method for knowing the hardness at your specific address is a physical measurement. Utility averages represent the system average; your tap can vary based on distribution zone, residence location relative to the wellfield, and seasonal aquifer changes.
Pure Agua Enterprises offers free in-home water testing across Kissimmee, St. Cloud, Celebration, Poinciana, and the surrounding Osceola County communities. A test takes 30 minutes and produces an on-site hardness reading, TDS measurement, and a review of what treatment, if any, would be appropriate for your home's specific water chemistry.
Schedule your free in-home water test or learn more about water softener options for Kissimmee homes.
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