What a Disinfection Byproduct Violation Notice Actually Means

Why the notice arrives months after the test

Compliance is not judged on a single sample. EPA sets a maximum contaminant level of 0.080 mg/L for total trihalomethanes and 0.060 mg/L for the five regulated haloacetic acids, and a system passes or fails on a locational running annual average of the four most recent quarters at each monitoring location.3

So one high quarter rarely triggers anything alone, and the violation is usually confirmed only when the fourth lands. Whitmire’s exceedance ran across four consecutive quarters ending September 30.23

Then a second clock starts. An exceedance like this is a Tier 2 notice under EPA’s Public Notification Rule, which allows up to 30 days from the point a system learns of it. Tier 1, the 24 hour category, is for acute hazards such as E. coli or nitrate.4 Our guide to what Tier 1, Tier 2 and Tier 3 mean covers the difference.

The pattern repeats. Goodyear, Arizona notified residents in May 2026, and its water services director explained that the rule is written as an annual average because this is not a contaminant that makes someone sick right away.10

Where trihalomethanes come from

Chlorine does the job it was added to do, then keeps reacting. Where it meets naturally occurring organic matter from the source water, part of that reaction produces trihalomethanes and haloacetic acids.35 There is no chlorinated tap water with zero byproducts, only more or less.

Two conditions push the numbers up. Warm water speeds the reaction, which is why a July through September quarter is often a system’s highest. Contact time does the rest: the farther water travels and the longer it sits in storage, the more time the reaction has. Small systems with long pipe runs are overrepresented in violation data.

Source water heavy with organic matter does the same, which is why a reservoir that has just turned over can lift byproduct formation for weeks. See what fall reservoir turnover does to your tap water.

This is the trade chlorination represents. Disinfection prevents outbreaks that were routine before it became standard, and byproducts are a lower grade concern measured in years rather than days, which is why the rule averages a year of samples.5

What the notice does and does not ask of you

Do not boil. This is the instruction people reverse most often. Boiling is right for a bacterial advisory and wrong here. Trihalomethanes are volatile, so heating drives them into the air of the room you are standing in, and what stays behind concentrates as the volume drops. If you are boiling for cooking anyway, Massachusetts health guidance suggests running an exhaust fan.5

The same volatility explains the shower advice in many notices. Ventilating the bathroom, shorter showers and a lower water heater setting all cut how much you inhale, a real exposure route alongside what you drink.5

If a notice says no alternative water source is necessary, read that as a statement about acute risk, not a dismissal of the finding. Massachusetts guidance still names bottled water as reasonable for pregnant women and for parents mixing formula.5 Decide for your own household, and raise specific health concerns with your physician.1

Read the notice you received, not the one you remember. A byproduct notice is not a boil water advisory, and the two ask for opposite actions. If you are unsure which you have, our boil advisory guide sets out what that one requires.

Find your water quality report ↗

For area level background, Epic’s What’s in Your Water lookup shows what has been reported near you. It is not a test of the water at your tap.

What a filter can and cannot do here

Byproducts are one category where home carbon filtration has real published performance behind it. Massachusetts guidance names granular activated carbon and reverse osmosis as technologies that reduce trihalomethane exposure, while noting that no filters are currently certified for HAA5.5

Epic’s independent laboratory testing on the Pure XP filter reports 99.4 percent reduction of trihalomethanes and 99.8 percent of haloacetic acids under test conditions.9 Those are independently tested results, not certifications. Pure XP’s official NSF listings cover Standard 42 for material safety and NSF/ANSI/CAN 372 for lead content.78 Keep the two apart.

Carbon is a consumable. Adsorption sites are finite, and a cartridge past its rated capacity stops performing long before it stops producing water. Pure XP is rated for 100 gallons, and gallons, not months is the number to track.

What a filter cannot do is fix the system. It does not move the running average, it does nothing about what you breathe in the shower, and it is no substitute for an official advisory. If a pitcher or dispenser fits your household, explore Epic’s pitchers, dispensers and bundles.