Overview
Trihalomethanes are disinfection by-products. They form when the chlorine used to keep water safe reacts with natural organic matter in the water. Utilities balance enough disinfection to kill germs against keeping by-products low.
In Florida, it was found in 1,329 community water systems serving about 21,273,042 people. 58 of those readings were above the federal legal limit, together serving 571,024 people.
The highest reading relative to the limit was at Sunshine Meadows in Palm Beach County, at 437% of it.
Where it comes from: By-product of drinking-water chlorination.
The standards
Legal limit (MCL)
80 ppb
Enforceable. A utility must stay at or under this.
Federal health goal (MCLG)
N/A ppb
Health-based, not enforceable. Often lower than the limit, sometimes zero.
Florida Water Report benchmark
0.06 ppb
Nobody has published a health goal for total trihalomethanes as a total. California has published one for each of the four compounds the total counts: bromodichloromethane 0.06 ppb, dibromochloromethane 0.1 ppb, chloroform 0.4 ppb and bromoform 0.5 ppb, all revised February 2020. Florida Water Report reads the total against the strictest of the four. EPA's own health goal for bromodichloromethane, and for bromoform, is zero. Source: California State Water Resources Control Board, MCLs, DLRs and PHGs for Regulated Drinking Water Contaminants, updated September 2025.
Health effects the EPA associates with it: May increase the risk of cancer. Liver, kidney, or central nervous system effects.
The health goal is set on health alone. The legal limit is set as close to it as is technically and economically feasible, so treatment cost and available technology are written into the number a utility is measured against. A system at or under the limit is meeting the standard it is required to meet. Both numbers are shown so the distance between them is visible.
What removes it
Activated carbon is the standard answer: trihalomethanes bind readily to it, so a carbon block at the tap or a whole-house carbon system reduces them. Reverse osmosis removes them too, mostly through its carbon prefilter rather than the membrane. A water softener does nothing here, because softening exchanges calcium and magnesium and does not touch organic chemistry. Trihalomethanes are also volatile, so a hot shower releases them into the air, which is the honest argument for treating where water enters the house rather than only at the kitchen sink.
Treatment guidance describes the methods generally used for this contaminant. What your own tap actually carries depends on your plumbing and your service line as much as on the utility, which is what a test at the house tells you and an annual report cannot.
Where in Florida
CountySystemsOver limit
Polk County641,933 people served1318Hillsborough County1,603,861 people served1585Putnam County26,168 people served305Volusia County543,519 people served454Broward County1,761,547 people served303Lake County396,676 people served973Osceola County322,991 people served273St. Johns County211,587 people served203Orange County1,601,660 people served412Brevard County701,961 people served252Nassau County59,492 people served112Miami-Dade County3,207,937 people served241Palm Beach County1,458,893 people served311Pinellas County1,147,776 people served121Seminole County508,185 people served361Pasco County382,268 people served481Collier County322,415 people served81St. Lucie County319,881 people served121Charlotte County245,625 people served181Marion County242,083 people served1011Martin County156,776 people served101Flagler County132,328 people served101Highlands County97,774 people served261Citrus County96,171 people served311Wakulla County30,119 people served71Columbia County21,308 people served171Taylor County11,291 people served31Liberty County6,879 people served81Glades County6,454 people served51Duval County932,389 people served21NoneLee County718,697 people served19NoneSarasota County477,177 people served13NoneManatee County428,473 people served7NoneEscambia County297,306 people served5NoneOkaloosa County280,106 people served20NoneLeon County225,620 people served10NoneAlachua County221,295 people served15NoneBay County204,814 people served10NoneClay County179,375 people served12NoneIndian River County164,201 people served2NoneSumter County160,281 people served22NoneHernando County145,810 people served8NoneSanta Rosa County134,834 people served9NoneWalton County107,016 people served5NoneHendry County32,262 people served9NoneOkeechobee County23,095 people served6NoneJackson County22,637 people served11NoneGulf County22,478 people served4NoneFranklin County22,212 people served6NoneGadsden County21,579 people served9NoneHardee County15,392 people served8NoneBradford County15,048 people served7NoneDesoto County13,031 people served6NoneLevy County12,772 people served12NoneSuwannee County12,510 people served6NoneBaker County10,228 people served4NoneDeSoto County8,942 people served1NoneWashington County8,715 people served5NoneMadison County8,180 people served3NoneHamilton County7,069 people served2NoneJefferson County6,044 people served3NoneUnion County4,875 people served2NoneDixie County4,750 people served3NoneCalhoun County4,300 people served2NoneGilchrist County3,174 people served2NoneLafayette County2,455 people served2NoneHolmes County658 people served2NoneKnow when your water changes
We will email you when new readings, violations or health goals land for your system.
Or schedule a water consultation.
Data Sources
EPA SDWISSystem identity, population, countyret. 2026
FDEPFlorida drinking-water chemical monitoringret. 2026
CCREach utility’s own annual reportret. 2026
CA OEHHACalifornia public health goals, the health-based benchmark where one is publishedret. 2026
FWROur own benchmarks, only where no government body has published one, each citing the official source it is built onret. 2026
These figures describe water as delivered by each utility, not what your home’s plumbing adds after it arrives. Informational; not a substitute for testing your own tap.
