If your annual water-quality report lists HAA5, it means your utility measured a group of five haloacetic acids that can form during drinking-water disinfection. The number homeowners usually need to know first is 60 µg/L, or approximately 60 ppb—EPA's Maximum Contaminant Level for HAA5.
But interpreting that number is not always as simple as comparing one test result with 60. EPA compliance is generally evaluated using a Locational Running Annual Average (LRAA), which accounts for results collected over time at individual monitoring locations.
This guide explains what HAA5 is, why it forms, how to read HAA5 results in your Consumer Confidence Report, what current research says about long-term exposure, and what to look for if you want additional at-home filtration.
Last reviewed: October 19, 2026. This guide is educational and is not medical advice.
HAA5 in Drinking Water: The Quick Answer
What is HAA5?
A group of five regulated haloacetic acids that can form when drinking-water disinfectants react with naturally occurring organic material.
What is EPA's limit?
60 µg/L, equal to 0.060 mg/L and approximately 60 parts per billion.
Does one result above 60 ppb mean a violation?
Not necessarily. Compliance under the Stage 2 DBPR is generally based on a location's running annual average.
Can home filtration reduce HAA5?
Some treatment technologies may reduce haloacetic acids, but performance varies significantly. Look for HAA-specific performance evidence rather than assuming all carbon filters perform the same way.
What Is HAA5?
HAA5 does not refer to a single chemical.
It is the regulatory name for the combined concentration of five haloacetic acids:
When a Consumer Confidence Report says, for example, “HAA5: 38 ppb,” that refers to the five compounds combined, rather than 38 ppb of one acid. Check the column heading: the figure may be an annual compliance average rather than an individual sample.
Other haloacetic acids can also occur in treated water, but the five above are the compounds included in the current federal HAA5 standard.
How Do Haloacetic Acids Get Into Drinking Water?
HAA5 is generally classified as a group of disinfection byproducts, or DBPs.
Haloacetic acids can form when disinfectants used during water treatment react with naturally occurring organic matter in source water.
Organic material enters source water
Natural organic matter can come from vegetation and other material in rivers, reservoirs, and other water sources.
The water is treated and disinfected
A disinfectant is used as part of the utility's treatment process.
Chemical reactions occur
The disinfectant can react with remaining organic matter.
DBPs can form
These reactions can produce HAA5, TTHMs, and other disinfection byproducts.
Haloacetic acids are therefore usually not deliberately added to the water. They are created through chemical reactions associated with disinfection.
Why Do HAA5 Levels Change Throughout the Year?
HAA5 is not necessarily present at exactly the same concentration every day.
Formation can be affected by several variables:
- Water temperature
- The amount and type of natural organic matter
- Source-water conditions
- Disinfectant type and dose
- pH and other water chemistry
- Treatment practices
- Storage conditions
- Time spent in the distribution system
Warmer conditions can accelerate many chemical reactions involved in disinfection-byproduct formation. Seasonal changes in rainfall, reservoir conditions, source-water blending, and organic material can also influence HAA5 levels.
Water age can matter as well. Reactions can continue while treated water travels through storage tanks and distribution pipes.
That helps explain why one monitoring location may report a different HAA5 concentration from another location served by the same utility.
What Is EPA’s Limit for HAA5?
Federal Maximum Contaminant Level for HAA5
60 µg/L = 0.060 mg/L ≈ 60 ppb
The EPA drinking-water standard applies to the combined concentration of the five regulated acids. It is not a separate 60 ppb allowance for each compound.
How annual averages affect compliance
Under the Stage 2 Disinfectants and Disinfection Byproducts Rule, compliance is generally evaluated using a Locational Running Annual Average (LRAA). For quarterly monitoring, this averages the quarterly results from the preceding four quarters at each monitoring location. Results from a low-reading location do not cancel out a high annual average at another.
One sample above 60 ppb does not necessarily establish an MCL violation, but it should not be ignored. It may require increased monitoring or an operational evaluation. Different provisions apply to reduced monitoring and incomplete monitoring records, so the utility and its regulator determine compliance under the applicable requirements.
How to Read HAA5 in Your Consumer Confidence Report
If you receive water from a community water system, start with your utility's annual Consumer Confidence Report (CCR).
HAA5 may appear under headings such as:
- Disinfection Byproducts
- Regulated Contaminants
- Detected Contaminants
- Water Quality Results
The contaminant itself may be labeled:
- HAA5
- Haloacetic Acids
- Haloacetic Acids (Five)
- Total Haloacetic Acids
Illustrative HAA5 water report
The following numbers are fictional and explain the reporting format; they do not describe your utility or current tap water.
| Contaminant | Highest LRAA | Range | MCL | Violation? |
|---|---|---|---|---|
| HAA5 | 41 ppb | 18–57 ppb | 60 ppb | No |
Here's how to interpret this example:
- 41 ppb is the highest reported locational running annual average.
- 18–57 ppb represents the range of individual results presented by the utility.
- 60 ppb is EPA's Maximum Contaminant Level.
- The utility reports no violation.
A CCR summarizes monitoring results and does not measure your tap’s concentration today. Read its sampling dates and footnotes.
Notice that the highest individual value in the range—57 ppb—is not necessarily the number used by itself to determine regulatory compliance.
What if you see an individual value above 60 ppb?
Before concluding that a violation occurred, determine what the number represents.
It could be:
- a single laboratory sample,
- a range maximum,
- a quarterly result,
- an Operational Evaluation Level, or
- the compliance LRAA.
If the report is unclear, ask the utility specifically:
“What was the HAA5 LRAA for the monitoring location serving my area, and was there an HAA5 MCL violation?”
What Are the Health Concerns?
EPA identifies increased cancer risk as a potential effect of drinking water with HAA5 above the MCL over many years. This describes a long-term exposure concern, not a prediction about one glass of water or an individual’s health. See EPA’s health-effects summary.
Health research includes animal studies of individual acids and observational studies of people exposed to mixtures of disinfection byproducts. These approaches answer different questions: a hazard identified experimentally does not by itself quantify the risk from a particular household’s tap water.
Human studies must account for changing water sources, exposure over time and other chemicals present alongside HAA5. An association involving a DBP mixture cannot automatically be attributed to HAA5 alone.
The 60 ppb standard is an enforceable regulatory limit, not a sharp boundary at which individual health effects suddenly begin. Use the concentration, duration of exposure and utility guidance together when deciding your next steps.
What About Pregnancy and Reproductive Health?
EPA’s DBP rules address concerns about potential cancer, reproductive and developmental effects. Research on pregnancy outcomes involves varying exposure estimates and mixtures of chemicals, so a particular HAA5 result cannot predict an individual pregnancy outcome. Read EPA’s Stage 2 rule overview.
If you are pregnant and your utility reports elevated HAA5 or issues a violation notice, follow its instructions and discuss any personal health concerns with your prenatal care provider. Do not switch to an untreated source simply to avoid disinfection byproducts; effective disinfection protects against waterborne illness.
HAA5 vs. TTHMs: What's the Difference?
If your water report contains HAA5, there is a good chance you will also see TTHMs.
Both are major regulated classes of disinfection byproducts, but they are chemically different.
| HAA5 | TTHMs | |
|---|---|---|
| What it represents | Five haloacetic acids | Four trihalomethanes |
| EPA MCL | 60 ppb | 80 ppb |
| Formed during disinfection? | Yes | Yes |
| Volatility | Generally much less volatile | More volatile |
| Compliance approach | LRAA | LRAA |
This difference in volatility matters.
TTHMs can contribute to exposure not only through ingestion but also through inhalation and other routes associated with activities such as showering.
Haloacetic acids are much less volatile, so ingestion of drinking water is generally the more relevant household exposure pathway for HAA5.
For a detailed explanation, see our Trihalomethanes (TTHMs) in Drinking Water Guide.
Should You Test Your Tap Water for HAA5?
For most households receiving municipal water, the Consumer Confidence Report is the logical first step.
Your utility's compliance monitoring provides more information about long-term HAA5 behavior across the distribution system than one isolated homeowner sample.
Additional testing may be useful when you have a specific question, such as:
- You want to know the concentration at your own tap.
- Your utility recently reported elevated HAA5 results.
- You live near the end of a distribution system or in an area with long water residence times.
- You want to compare unfiltered and filtered water.
- You are evaluating a filtration system's real-world performance.
Use a qualified drinking-water laboratory
HAA5 is not a good candidate for an ordinary home test strip.
Choose a drinking-water laboratory certified by your state for the relevant HAA analysis. Request HAA5, with the individual compounds and their combined result. If the lab offers HAA9, ask it to identify the HAA5 subtotal separately; HAA9 includes additional acids and is not directly interchangeable with the regulated HAA5 sum.
Order the laboratory’s sampling kit before collecting water. Follow its exact instructions for bottles, preservatives or disinfectant quenchers, collection, cooling and delivery deadlines. Do not rinse out prepared bottles or substitute a household container.
Ask about reporting limits and how nondetects are handled in the total. A result below a reporting limit does not prove that a compound is completely absent. Chlorine strips, taste, smell and a TDS meter cannot measure HAA5.
If evaluating a filter, consider collecting:
Ask the lab how to collect paired samples from the same source water. Record the filter model, installation date, and approximate gallons treated. A paired test shows performance at that time; follow-up testing as the filter ages is needed to assess whether the reduction continues.
Can HAA5 Be Reduced With a Home Water Filter?
Potentially—but HAA5 filtration claims deserve more scrutiny than generic “carbon filter” claims.
Haloacetic acids have different chemical behavior from TTHMs. You should therefore not assume that a product shown to reduce chlorine or TTHMs automatically provides the same reduction for HAA5.
| Technology | What homeowners should know |
|---|---|
| Activated carbon | Carbon adsorption is widely used for many organic compounds and DBPs, but HAA performance can depend considerably on carbon type, system design, water chemistry, contact time, and individual haloacetic acid. Look for HAA-specific test data. |
| Reverse osmosis | Membrane systems can reduce a wide range of dissolved substances, but actual HAA performance varies by system. Review contaminant-specific performance information rather than relying solely on the term “reverse osmosis.” |
| Specialty treatment media | Some systems use adsorption or other media targeted toward organic contaminants. Performance evidence should identify the actual compounds tested. |
| Generic pitcher/refrigerator filter | Do not assume HAA5 reduction simply because the product contains activated carbon or reduces chlorine taste and odor. |
What should you look for before buying?
- Does the performance report specifically mention haloacetic acids, HAA5, DCAA, TCAA, MCAA, MBAA or DBAA?
- What concentrations were used during testing?
- How much reduction occurred?
- Was performance tested through the filter's rated service life?
- Was testing performed by an independent laboratory?
- What flow rate or contact time was used?
- How often does the filter need to be replaced?
Black Berkey® and Phoenix Gravity: What Does the HAA Evidence Show?
Both Black Berkey® Elements and Phoenix Gravity New Millennium Edition™ elements have published independent laboratory reports addressing disinfection byproducts. The specific compounds and test conditions matter when interpreting those reports.
Black Berkey® Elements: direct HAA5 evidence
The manufacturer’s Black Berkey evidence library includes a County of Los Angeles Environmental Toxicology Laboratory report dated August 22, 2012. Page 4 lists all five regulated haloacetic acids using Method 552.2, as well as a separate total HAA5 row. This is HAA-specific evidence, not simply an inference from TTHM reduction.
For the individual compounds, the report lists 50 µg/L before filtration, with results below 2 µg/L for monochloroacetic acid and below 1 µg/L for each of the other four acids. Those values correspond to greater than 96% and greater than 98% reduction, respectively, under the reported test conditions.
The total HAA5 row lists values from 50 µg/L down to below 1 µg/L. Because that starting total is not the sum of the five displayed individual starting concentrations, the table should not be reconstructed as one combined-mixture mass balance. These results establish reported laboratory reduction, not HAA5 performance throughout the elements’ full advertised service life.
Phoenix Gravity: distinguish other haloacetic acids from HAA5
The September 28, 2025 RAYNU report for Phoenix PGF9-2 includes an initial-test result for tribromoacetic acid, a haloacetic acid that is not one of the five compounds in HAA5. It reports a decrease from 10 mg/L to below 0.1 mg/L. That finding is relevant to the tested acid, but does not by itself establish reduction of the regulated HAA5 group.
Neither these laboratory results nor a general chlorine-reduction certification should be described as HAA5 certification. Do not transfer one element’s percentages or tested service volume to the other.
Our filter test-results reference brings together reports for both element types. For availability and compatibility, use the replacement filters page.
What Should You Do If Your Water Report Shows HAA5?
Find the HAA5 entry.
Look under disinfection byproducts or regulated contaminants.
Confirm the units.
60 µg/L is equivalent to 0.060 mg/L and approximately 60 ppb.
Identify what the reported value represents.
Determine whether you're looking at an individual result, a range, an LRAA, or the Highest LRAA.
Check the violation column.
Do not conclude that one unusual result automatically represents regulatory noncompliance.
Ask the utility about your area if necessary.
HAA5 can vary among distribution-system monitoring locations.
If you want an additional reduction, evaluate evidence for HAA-specific filtration.
Do not assume chlorine or TTHM performance automatically establishes HAA5 performance.
Frequently Asked Questions About HAA5
What does HAA5 stand for?
HAA5 refers to five regulated haloacetic acids: monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid.
What is EPA's limit for HAA5?
EPA's Maximum Contaminant Level is 0.060 mg/L, which equals 60 µg/L and approximately 60 parts per billion.
Is HAA5 the same as chlorine?
No. Chlorine can be used as a disinfectant during water treatment. HAA5 refers to chemical byproducts that can form when disinfectants react with naturally occurring organic material.
Is HAA5 the same as TTHMs?
No. Both are regulated groups of disinfection byproducts, but HAA5 contains five haloacetic acids while TTHMs contain four trihalomethanes. EPA's current MCL is 60 ppb for HAA5 and 80 ppb for TTHMs.
Why does my water report show only one HAA5 number?
Because HAA5 is regulated as the combined concentration of five haloacetic acids. Utilities commonly report the total rather than displaying all five compounds individually.
Does one HAA5 test above 60 ppb mean my utility violated EPA rules?
Not necessarily. Stage 2 DBPR compliance is generally determined using a Locational Running Annual Average for each monitoring location. Check whether the value you see is an individual result, range maximum, LRAA or another measurement.
Why can HAA5 be higher during some parts of the year?
HAA5 formation can vary with temperature, natural organic matter, treatment conditions, source-water changes, water chemistry and distribution-system residence time. Seasonal variation is therefore common.
Can I taste or smell HAA5?
HAA5 at drinking-water concentrations should not be evaluated by taste or smell. A noticeable chlorine taste or odor does not tell you how much HAA5 is present.
Are HAA5 levels the same throughout my city?
Not necessarily. HAA5 can vary among monitoring locations because water age, temperature, source-water blending and other distribution-system conditions can differ.
Should I test my own tap water for HAA5?
Your utility's Consumer Confidence Report is generally the best first step. Laboratory testing may be useful if you want a tap-specific result, are investigating reported elevated levels, or want to compare unfiltered and filtered water.
Can activated carbon reduce HAA5?
Some carbon-based treatment systems may reduce certain haloacetic acids, but performance depends on the carbon, filter design, contact time, water chemistry and individual compound. Look for HAA-specific performance data rather than assuming all activated-carbon filters work equally well.
Does a filter that reduces TTHMs automatically reduce HAA5?
No. TTHMs and HAA5 are chemically different groups of disinfection byproducts. Performance testing for one group should not automatically be treated as performance evidence for the other.
Do Berkey® filters reduce HAA5?
Black Berkey® Elements have published laboratory results for all five HAA5 acids. The Phoenix report discussed above includes tribromoacetic acid, which is outside the regulated HAA5 group. Review the element-specific evidence and its limits; neither result should be treated as a guarantee of HAA5 reduction throughout the filter’s full advertised life.
Do private wells contain HAA5?
HAA5 is primarily associated with water that has undergone disinfection involving reactive disinfectants and organic material. A typical untreated private well does not have the same treatment process as a municipal system, although individual treatment systems can differ.
Does Boiling Remove HAA5?
Do not rely on boiling as a household HAA5 treatment. Heating can change the mix of disinfection byproducts, and reducing volatile THMs does not establish removal of the less volatile haloacetic acids. Research on boiling and disinfection byproducts examines these compound-specific changes.
If a boil-water advisory is issued for a microbial problem, follow that advisory. A microbial advisory and an HAA5 violation require different responses.