Why Orlando's Water Treatment Switches Every Year (And What You Smell When It Happens)

If Orlando's tap water suddenly smells like a swimming pool for a few weeks each year, you are noticing the annual free-chlorine burnout that OUC and Toho run to flush their distribution systems. It is safe, it is planned, and it ends. Here is what is happening, why utilities do it, and how to remove the taste at home with the right kind of carbon filter.

Chloramine versus free chlorine, the basics

Every municipal water system in Central Florida disinfects the water before it leaves the treatment plant. The disinfectant has to stay active all the way through miles of distribution pipe so that the water reaching your kitchen tap is still microbiologically safe. Two chemistries do that work, and OUC, Orange County Utilities, and Toho Water Authority all use the same two, just on different schedules.

Free chlorine is what most of us picture when we think of pool water. It is a fast, aggressive disinfectant that reacts quickly with anything organic. It also has that unmistakable swimming-pool smell because free chlorine off-gasses readily from open water and reacts with skin oils, hair proteins, and any organic film inside the plumbing.

Chloramine is chlorine combined with a small amount of ammonia. The reaction produces a much more stable molecule (monochloramine) that lasts longer in the pipes and produces far fewer trihalomethane and haloacetic-acid disinfection byproducts than free chlorine. At normal maintained levels, chloramine is essentially odorless and tasteless. Most Central Florida residents do not consciously notice the disinfectant in their water at all, because the year-round disinfectant is chloramine.

That is why the swimming-pool smell, when it does show up, is so obvious. You are not used to it. The utility deliberately switched chemistries for a few weeks, and your nose is correctly reporting that the water now contains free chlorine instead of chloramine.

Why utilities switch, the nitrification problem

Chloramine is the better year-round disinfectant for one reason and the worse year-round disinfectant for another. The good: it is stable, long-lasting, and produces few regulated byproducts. The bad: when chloramine concentration drops too low somewhere in the distribution system (a dead-end main, a low-flow neighborhood, a long stretch of pipe in summer heat), the ammonia portion of the molecule becomes available to nitrifying bacteria.

Those bacteria convert the ammonia first to nitrite and then to nitrate. The process is called nitrification, and once it gets a foothold in a section of pipe it accelerates: the bacteria consume more chloramine, the disinfectant level falls further, and the bacterial colony grows. The American Water Works Association documents nitrification as the single most common operational headache for utilities that run on chloramine year round.

The textbook fix, and the one OUC and Toho both use, is a periodic free-chlorine conversion. The utility temporarily switches the disinfectant from chloramine back to plain free chlorine. Free chlorine kills the nitrifying bacteria, oxidizes the accumulated biofilm on pipe walls, and resets the distribution system. Once the conversion period ends, the utility returns to chloramine and the system runs cleanly for another year. The EPA recognizes the practice and describes it in guidance for chloraminated systems.

OUC's annual schedule, and Toho's

Orlando Utilities Commission publishes the free-chlorine conversion dates on its water-quality page each year. The conversion typically runs four to six weeks, most commonly late winter into early spring, before the peak summer demand and warmer source-water temperatures kick in. Toho Water Authority follows a similar schedule for the Kissimmee, Poinciana, and unincorporated Osceola service area, with the exact window varying by year and by treatment plant.

Orange County Utilities, Winter Park Utilities, Sanford, and the smaller systems each set their own conversion windows. Some announce the dates in advance on the utility website and in the annual Consumer Confidence Report; others post a notice only after the conversion begins. If you want the exact window for your address in any given year, pull your utility's water-quality page or call the utility hotline. The dates move year to year.

During the conversion the disinfectant residual in the pipes is free chlorine at the EPA-allowed range (up to 4 mg/L), not the lower steady-state chloramine residual you are used to. Some hydrants are flushed during the same window, which can stir up sediment in the mains and produce a brief discolored-water episode in some neighborhoods. The discoloration is cosmetic and clears within a few minutes of running the cold tap.

What you will notice at home

The pool-water smell is the obvious signal, but the conversion period shows up in a few other ways too. Reading the pattern helps confirm what you are smelling is the utility conversion and not a problem inside your house.

Smell: A clear chlorine note at the cold tap, strongest first thing in the morning before the line has flushed. The smell intensifies in a steamy shower because warm water releases more free chlorine to the air.

Taste: A sharper, more medicinal taste in drinking water and in anything you make with tap water, especially tea and coffee. Some people notice it more in ice cubes made during the conversion period than in the freshly poured glass.

Hair and skin: Drier skin after showering, a duller feeling in long hair, and a noticeable difference in how shampoo lathers. Free chlorine is rougher on keratin than chloramine. The effect reverses when the utility returns to chloramine.

Aquariums and ponds: Standard dechlorinator drops dosed for chloramine may underdose during the free-chlorine window. Read the bottle. Many products list a separate, lower dose for free chlorine. If you keep fish, this is the most important seasonal check on this list.

Kidney dialysis at home and certain medical equipment: If a household member uses home dialysis or any equipment with a chloramine-removal pre-treatment, the equipment vendor's protocol almost always covers both chemistries, but it is worth confirming with the clinical team during the conversion window.

For the broader Central Florida disinfection picture, including how Toho and OUC compare on byproducts and source water, see our chloramine vs ozone background piece and the Kissimmee and Orlando water quality guide.

Is it safe? Yes.

The free-chlorine concentration during the conversion stays inside the EPA Maximum Residual Disinfectant Level of 4 mg/L. That is the same regulatory ceiling that applies to free chlorine in any U.S. water system, including the dozens of large utilities that run on free chlorine year round. The water is microbiologically safer during the conversion, not less safe, because the higher-redox disinfectant is actively scrubbing the distribution system.

The aesthetic effects (taste, smell, hair feel) are real but are not health effects. The EPA's secondary drinking-water guidance recognizes the taste and odor as nuisance factors at residuals above roughly 0.6 to 1 mg/L. Utilities publish the conversion in advance for exactly this reason: so residents who notice the change have context and do not assume something has gone wrong with the supply.

Two narrow exceptions, both already covered above: keep aquariums and any medical equipment on the correct dechlorination protocol for whichever disinfectant the utility is currently using. Everything else, drinking, cooking, bathing, laundry, lawn watering, runs the same as the rest of the year.

The fix at home, the right kind of carbon

If the seasonal pool-water smell bothers you (or if you want the chloramine residual gone year round for taste, hair, and skin reasons), point-of-entry carbon filtration is the answer. The catch is that the carbon has to match the disinfectant.

Standard granular activated carbon (GAC) removes free chlorine fast. A 10-inch GAC cartridge can knock free chlorine to non-detect at typical residential flow rates with empty-bed contact times under a minute. If your only goal is to handle the four-to-six-week conversion period, an under-sink GAC stage on the kitchen tap covers it for the cost of a single cartridge change.

Catalytic carbon is GAC that has been steam-activated to give the carbon surface enzymatic activity for breaking the chloramine molecule apart. Catalytic carbon removes chloramine effectively at residential contact times. Standard GAC does not; it will adsorb a small fraction and then leak chloramine through the bed. If you want a single whole-house solution that handles both the year-round chloramine and the annual free-chlorine window, catalytic carbon is the right media. Most quality whole-home stacks in Central Florida use a 1 to 1.5 cubic-foot catalytic carbon tank ahead of the softener.

A few practical notes on sizing. The whole-house catalytic carbon tank should be sized to your peak flow, not your average flow. A family-of-four house with two showers running at once needs about 8 to 10 gpm of capacity at the carbon stage; undersizing pushes contact time below what catalytic carbon needs to break chloramine cleanly. The carbon bed in a properly sized residential tank typically runs 5 to 7 years before media change. If your stack already includes catalytic carbon and the seasonal free-chlorine smell is still bleeding through, the bed is exhausted and is the priority service item.

For an under-sink-only solution, a reverse osmosis system with a quality carbon pre-filter and a carbon post-filter removes both chloramine and free chlorine from drinking water specifically, even if the rest of the house still gets the seasonal pool smell at the shower. The RO pillar covers point-of-use chemistry; the hard water pillar covers the upstream softener question.

Recommended method: matching the situation to the fix

What you have at home	What you notice during the burnout	Right fix
OUC or Toho city water, no whole-house filter	Pool-water smell at every tap for 4 to 6 weeks	Whole-home catalytic carbon stack, sized to peak flow; covers chloramine year round and free chlorine during the burnout
City water with an existing standard GAC carbon stage	Bigger pool smell than usual during the burnout, fine the rest of the year	Replace the GAC bed with catalytic carbon at the next service, or add catalytic carbon downstream
City water with under-sink RO only, no whole-house filter	Drinking water tastes fine, shower and laundry smell like chlorine	Add a point-of-entry catalytic carbon stage; keep the RO for drinking water polish
Aquarium or pond keeper	Fish stress, cloudy water, or unexplained fish loss in late winter	Confirm dechlorinator dose for both free chlorine and chloramine; consider a dedicated dechlor stage on the fill line
Vacation home or short-term rental sitting empty during the burnout	Heavy chlorine smell when guests arrive, brown water at first flush	Flush every fixture 3 to 5 minutes before guest arrival; install whole-home catalytic carbon for unattended periods
Private well on Floridan Aquifer (no city disinfection)	No burnout smell, but other diagnostics may apply	See the Florida well water guide for the well-specific stack

Call a professional if...

• The chlorine smell persists for more than 8 weeks. Utility burnouts run 4 to 6 weeks. A longer-running smell suggests either a local nitrification issue the utility is still working through, or an in-home cause unrelated to the conversion.
• The smell is concentrated at one bathroom, not whole-house. That points to a branch-line or fixture issue (a contaminated showerhead biofilm, a dead-leg in the plumbing), not the utility chemistry.
• You see brown or yellow water at the cold tap during the burnout. Most likely a hydrant-flush event in your neighborhood; if it does not clear in 30 minutes of flushing, call the utility and report it.
• Your aquarium fish show stress or loss after a water change. Stop using straight tap water for changes until you confirm dechlorinator dosing for free chlorine, and consider a dedicated dechlor pre-stage.
• Your catalytic carbon stack is older than 6 to 7 years and the seasonal smell is breaking through. The media bed is at end of life; the fix is a media change, not adding more equipment.
• You have eczema, asthma, or chemical sensitivity and notice a flare during the burnout. Document the timing for your physician and prioritize point-of-entry chloramine removal year round.
• You run a home dialysis unit or any medical equipment with a chloramine pre-treatment. Confirm the manufacturer's protocol for the free-chlorine window with your clinical team before the conversion begins.

Frequently asked questions

What to do next

If you have noticed the seasonal pool-water smell and you want it gone (this year, next year, every year), the first step is a free in-home water test. The Pure Agua Enterprises team will measure chloramine or free chlorine at the kitchen tap, hardness, iron, and pH, confirm which utility serves your address, and tell you whether a catalytic carbon stage on its own is enough or whether a full softener-plus-catalytic stack makes more sense for your home. Family-owned since 2016, 200+ five-star reviews, NSF/WQA certified equipment, Florida licensed.

Background reading on Central Florida water: the Central Florida hard water guide, the Florida well water guide, the RO drinking water guide, the Kissimmee and Orlando water quality guide, the Floridan Aquifer hard water article, the chloramine vs ozone background, the rotten-egg smell diagnostic, the general smell and staining diagnostic, the hard water stains on glass diagnostic, the complete softener guide, the Central Florida softener cost guide, the vacation rental water guide, the 200 installs patterns piece, the service area page, the service areas index, the about page, the financing options, and the FAQ.

Call (407) 512-8342 or request your free in-home water test. We arrive with a calibrated chlorine and chloramine test, a hardness test, and a pH meter. Test on the spot, written diagnosis, no pressure.