Whole Home CompanyCheck your water

Guide · updated November 2, 2026

What are HAA9 and TTHM in Florida tap water?

HAA9 (haloacetic acids) and TTHM (total trihalomethanes) are disinfection by-products. They form when the chlorine or chloramine used to disinfect city water reacts with natural matter in the source water. Every one of the 25 large Florida systems in our report has them above EWG's health guidelines, while staying within the federal limits that apply to them.

Why they're in the water

Utilities disinfect water so it stays clean on the way to your tap. Florida's source water often carries natural organic matter, and when disinfectant meets it, by-products form. That's why they show up across the state rather than in one place.

The limits

  • TTHM: the federal limit is 80 parts per billion, as a running annual average.
  • HAA5 (five of the haloacetic acids): the federal limit is 60 parts per billion.
  • HAA9 (all nine haloacetic acids): no federal limit.
  • EWG's health guidelines for these are far lower than the legal limits, so a system can be within the law and well above the guideline at the same time.

The highest HAA9 and TTHM results in our Florida report

Highest HAA9 or TTHM result per system, utility testing averages (EWG Tap Water Database, compiled October 2026)
Water systemBy-productAverageTimes EWG guidelineFederal limit
Manatee County UtilitiesBradentonHAA961.7 ppb1,029×No federal limit
Orange County Utilities EastOrlandoHAA945.3 ppb754×No federal limit
City of CocoaCocoaHAA943.5 ppb724×No federal limit
Toho Water Authority EasternKissimmeeHAA932.9 ppb548×No federal limit
Orlando Utilities CommissionOrlandoHAA932.7 ppb544×No federal limit
City of LakelandLakelandHAA932.0 ppb533×No federal limit
Pinellas County UtilitiesClearwaterHAA929.1 ppb486×No federal limit
Charlotte County UtilitiesPort CharlotteHAA924.9 ppb415×No federal limit

What reduces them at home

Carbon filtration is the most common way to reduce disinfection by-products, along with chlorine and chloramine. A whole-house carbon system covers every tap and shower; a reverse osmosis tap goes further at the kitchen sink. Every Whole Home package includes a whole-home carbon stage.

Short answers

Is HAA9 regulated?

Not as a group. Federal rules set a limit for HAA5, five of the nine haloacetic acids, at 60 parts per billion. HAA9 has no federal limit.

Why does my utility say the water meets standards?

Because it does: the federal limits are the legal standard, and the averages in our report are within them for TTHM and HAA5. EWG's health guidelines are a stricter, independent benchmark.

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Related: Chloramine vs. chlorine: what Florida homeowners should know before buying a filter · Water softener vs. whole-house filter vs. salt-free conditioner: which do you need?

Source: EWG Tap Water Database, compiled October 2026. EWG's health guidelines are far stricter than federal legal limits. Long-term averages describe the public supply, not any one home, and aren't the same as current compliance; see your utility's latest annual water quality report. Whole Home Company sells and installs home water treatment and isn't affiliated with any utility or with EWG.