Most Central Florida homeowners assume drinking water is "chlorinated" and leave it at that. For most homes that is right: OUC, Toho Water Authority and Orange County Utilities all use chlorine as the residual disinfectant. But they get there in different ways, and one Toho system uses chloramine instead. The difference determines whether your home carbon filter is doing its job or quietly letting disinfection residuals through.
How Each Utility Disinfects
OUC, Ozone Primary + Chlorine Residual
Orlando Utilities Commission treats its water with ozone (O₃) and then adds chlorine to maintain a residual in the distribution system. OUC says it uses ozone to remove unpleasant tastes and odors, and it answers "No" to "Does OUC use chloramines?" (ouc.com/about/water-services). Because ozone decomposes rapidly back into oxygen, it leaves no persistent residual of its own; that is why chlorine is added after it.
For OUC customers, the water reaching your tap carries a free chlorine residual, not chloramines. This matters because free chlorine is easy to remove with standard activated carbon filtration at residential flow rates.
Toho Water Authority, Chlorine (Chloramine in Harmony)
Toho Water Authority, which serves Kissimmee, St. Cloud, Poinciana and unincorporated Osceola County, says in its FAQ that only chlorine is added to its water. Its 2025 water quality reports list chlorine for the Eastern, Poinciana, St. Cloud, Western, Hidden Glen and Sunbridge systems. The exception is the Harmony water system, which reports chloramines, a combination of chlorine and ammonia (tohowater.com/waterquality).
For most Toho customers, the water reaching your tap carries a free chlorine residual, which standard carbon removes easily. Homes on the Harmony system carry a chloramine residual, which is fundamentally harder to remove with standard carbon.
Orange County Utilities, Free Chlorine
Orange County Utilities, separate from OUC, serves unincorporated Orange County. Its 2025 water quality report lists chlorine as the disinfectant for each of its systems (OCU 2025 water quality report).
Typical Residual Levels
EPA sets a Maximum Residual Disinfectant Level (MRDL) of 4.0 ppm for both chlorine and chloramines in finished drinking water. The 2025 reports and utility FAQs give these levels:
- Chlorine (Toho, 2025 running annual averages): 1.57 to 1.83 ppm in the Central, Southern, St. Cloud and Western reports
- Chloramines (Toho Harmony system, 2025): 3.0 ppm running annual average
- Chlorine (OUC): 1.0 ppm average, per OUC's FAQ
- Chlorine (Orange County Utilities, 2025): system averages from 0.90 to 2.65 ppm
Why the Distinction Matters for Home Filtration
Standard granular activated carbon (GAC) removes free chlorine through a fast surface reaction, water contacts carbon, chlorine is reduced to chloride, and filtered water exits. Typical residential GAC removes 90%+ of chlorine at normal flow rates.
Chloramines don't work that way. The N-Cl bond in monochloramine (NH₂Cl) is far more stable, and removing it requires chemical decomposition rather than simple adsorption. Published performance data:
- Standard GAC on chloramine: 40, 65% removal at residential flow, much lower than chlorine removal, and it drops further as the carbon ages.
- Catalytic carbon on chloramine: 90%+ removal. The media surface is specifically treated to catalyze the chloramine decomposition reaction.
If you're on Toho's Harmony system, or any chloraminated supply, and you bought a "chlorine taste and odor" filter, you're probably getting significantly less chloramine removal than you think. After 6 to 12 months of use, most standard GAC units are pass-through for chloramine.
Practical Selection Guide
OUC customer: Standard GAC whole-house filter works for chlorine. Consider an under-sink RO for drinking water quality (DBPs, trace contaminants). The ozone upstream means your water already has lower H₂S and lower overall organic loading.
Toho Water customer: Most Toho systems use chlorine, so standard GAC works as it does for OUC. On the Harmony system you need catalytic carbon media, not standard GAC, for whole-house chloramine removal; NSF/ANSI 42 certification for chloramine reduction is the standard to look for. An under-sink RO adds a second barrier for drinking water.
Orange County Utilities customer: Same approach as OUC: free chlorine is removable with standard GAC. Check the PFAS section of the latest OCU report; an under-sink RO is the most effective home option if you want PFAS reduction in drinking water.
How to Verify Your Disinfectant
Three ways:
- Your utility's CCR. The annual Consumer Confidence Report identifies the primary disinfectant. Published by July 1 each year.
- Simple home test strips. Total chlorine vs. free chlorine strips are cheap. If total chlorine is significantly higher than free chlorine, you have chloramines (the difference is combined chlorine = chloramines).
- Ask a water professional. Pure Agua tests chloramine specifically during free water testing.
Aquarium and Pond Owners
Chloramines are acutely toxic to fish at normal residual levels, which matters if you are on Harmony water or another chloraminated supply. Unlike free chlorine, chloramines do not off-gas from standing water within hours, they persist for days. Dechlorination conditioners specifically formulated for chloramines (not just chlorine) are required for every water change.
OUC's ozone-primary approach doesn't reach aquariums, by the time water reaches your tap, you're dealing with the free chlorine residual added at the end of treatment. Standard aquarium conditioners handle this fine.
Get Your Water Tested
Pure Agua provides free in-home water testing throughout Osceola, Orange, and Seminole Counties, we measure your exact chloramine or chlorine residual, hardness, pH, and TDS, and we know the differences between Toho Water, OUC, and OCU service areas. 5.0★ rated with 200+ Google reviews. Family-owned since 2016.
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