Haloacetic acids, often called HAAs, are disinfection byproducts that can form during public water treatment when disinfectants react with naturally occurring organic matter in source water. The federally regulated group HAA5 has an EPA maximum contaminant level of 0.060 mg/L (60 µg/L).
Can haloacetic acids be reduced at home? Yes. Treatment options can include activated-carbon-based filtration and other systems with documented HAA reduction performance. Start by checking your Consumer Confidence Report for HAA5, then compare your concern with contaminant-specific filter test results rather than assuming every carbon filter performs the same way.
What Are Haloacetic Acids?
Haloacetic acids are chemical byproducts that may form when disinfectants such as chlorine react with natural organic material in water. This material can come from leaves, soil, algae, and other organic matter found in source water.
The federally regulated group known as HAA5 includes five haloacetic acids:
- Monochloroacetic acid (MCAA)
- Dichloroacetic acid (DCAA)
- Trichloroacetic acid (TCAA)
- Monobromoacetic acid (MBAA)
- Dibromoacetic acid (DBAA)
The broader term haloacetic acids can refer to additional compounds beyond these five. HAA5 specifically refers to the five compounds grouped together under the current federal drinking-water standard.
HAAs belong to the broader category of disinfection byproducts (DBPs). Another regulated DBP group is total trihalomethanes (TTHMs).
How Do Haloacetic Acids Form?
Disinfection is an important part of public water treatment. Utilities use disinfectants to control contaminants and maintain water quality as treated water moves through the distribution system.
HAAs can form when disinfectants react with naturally occurring organic material. Formation can be influenced by:
- The amount and character of organic matter in the source water
- The type and amount of disinfectant used
- Water temperature
- pH
- Time spent in storage and the distribution system
- The presence of bromide in source water
Because these conditions change, HAA levels can vary by season and by location within a distribution system.
Why Does EPA Regulate HAA5?
EPA regulates HAA5 in public drinking-water systems. The current maximum contaminant level (MCL) is 0.060 mg/L, equivalent to 60 µg/L or 60 ppb. EPA identifies increased risk of cancer as the potential health effect associated with long-term exposure above the MCL.
| EPA-regulated DBP group | Current MCL | Equivalent concentration |
|---|---|---|
| HAA5 | 0.060 mg/L | 60 µg/L (60 ppb) |
| Total Trihalomethanes (TTHMs) | 0.080 mg/L | 80 µg/L (80 ppb) |
A detected HAA5 value does not, by itself, mean that a public water system is out of compliance. Utilities monitor these compounds under federal drinking-water rules, and compliance is evaluated according to the applicable monitoring and averaging requirements.
How to Find Out Whether Your Water Contains HAA5
If your home receives public water, start with your utility's Consumer Confidence Report (CCR), also called an annual drinking-water quality report. Look for:
- Haloacetic Acids
- HAA5
- Total Haloacetic Acids
- Disinfection Byproducts
- Stage 2 Disinfectants and Disinfection Byproducts Rule
Because HAA5 can vary seasonally and throughout a distribution system, ask your utility about monitoring locations and seasonal results if the reported value raises questions.
For a more specific measurement at your tap, contact an appropriately qualified drinking-water laboratory and follow its sample-container, preservation, and handling instructions.
How to Remove or Reduce Haloacetic Acids at Home
The most useful approach is to choose treatment based on documented HAA performance. A broad statement such as “activated carbon filter” does not specify how a particular filter will perform with respect to HAA5.
1. Activated Carbon Filtration
Activated carbon is widely used for organic compounds and drinking-water taste and odor concerns. HAA performance depends on the carbon media, filter design, contact time, flow rate, incoming water chemistry, service volume, and maintenance. Look for testing that specifically identifies HAA5 or the individual haloacetic acids of concern.
2. Whole-House Carbon Systems
Some households consider whole-house carbon treatment when the goal is to address disinfection byproducts at multiple fixtures. Proper sizing, contact time, flow rate, installation, and media replacement are important to performance.
3. Reverse Osmosis Systems
Reverse-osmosis systems combine a membrane with prefilters and often post-filters. Performance varies by system and configuration, so HAA-related claims should be evaluated using contaminant-specific performance documentation rather than assuming all RO systems provide the same result.
4. Gravity-Fed Filtration
Countertop gravity-fed systems provide point-of-use treatment without the need for permanent plumbing installation. If HAA5 is your concern, use the laboratory evidence for the exact filter element installed in the system.
Black Berkey® Elements and HAA5
Yes—Black Berkey® Elements have independent HAA5 reduction evidence. Published independent testing using EPA Method 552.2 reported Total Haloacetic Acids (HAA5) challenged at 50 µg/L and reported at <1 µg/L after filtration, or >98% reduction, under the documented test conditions.
The same testing reported results for individual haloacetic acids including bromoacetic acid, dibromoacetic acid, dichloroacetic acid, and chloroacetic acid. These laboratory results apply to the tested sample and conditions described in the report and should not be treated as a guarantee for every water source or operating condition.
Black Berkey® Elements remain installed in many existing Berkey® systems. If you currently use Black Berkey® Elements, the availability of newer replacement elements does not erase the test evidence for the filters already in your system.
What About Phoenix Gravity Elements?
Phoenix Gravity New Millennium Edition™ Filter Elements have undergone more recent independent testing covering multiple disinfection byproducts and organic contaminants. However, the currently published Phoenix evidence should be evaluated on a per-analyte basis; a general DBP result should not automatically be described as an HAA5 result unless the underlying report specifically identifies HAA5 or an individual HAA compound.
For current Phoenix and Black Berkey® evidence, see our Berkey® Filter Test Results. If your Black Berkey® Elements eventually need replacement, Phoenix Gravity New Millennium Edition™ Filter Elements are the current compatible primary replacement option for stainless-steel Berkey® systems.
Certification and independent testing are different. The HAA5 result discussed above is independent laboratory evidence for Black Berkey® Elements. It should not be described as NSF certification for HAA5 reduction.
Steps to Address an HAA5 Concern
- Review your Consumer Confidence Report. Find the HAA5 result and units.
- Put the number in context. EPA's current HAA5 MCL is 60 µg/L.
- Ask your utility questions. HAA5 can vary by season and monitoring location.
- Test when appropriate. A qualified laboratory can provide a tap-specific measurement.
- Compare contaminant-specific filter evidence. Look for HAA5 or the exact HAA compounds rather than broad filtration claims.
- Maintain the filter correctly. Follow the installation, cleaning, service life, and replacement instructions for the exact element you use.
What Utilities Do to Manage HAAs
Public water systems manage disinfection byproducts while also maintaining effective disinfection. Depending on the system, strategies can include:
- Improving removal of organic matter before disinfection
- Optimizing disinfectant application
- Managing water age in storage tanks and distribution lines
- Monitoring seasonal changes in source water
- Adjusting treatment processes while maintaining required disinfection
HAA5 vs. TTHMs
HAA5 and TTHMs are different groups of disinfection byproducts, although both can form when disinfectants react with naturally occurring material in water. EPA's current MCL is 60 µg/L for HAA5 and 80 µg/L for TTHMs.
Because the two groups share related formation conditions, Consumer Confidence Reports commonly list both. See our Trihalomethanes (TTHMs) in Drinking Water Guide for the companion topic.
You may also want to review our guides to chlorine in drinking water and chloramine in drinking water to understand the disinfectants used by many public water systems.
Important Notes About Water Filter Claims
Do not rely only on broad marketing language when choosing a filter. Useful evidence identifies the contaminant, challenge concentration, effluent concentration or reduction, test method, service volume, and other relevant test conditions.
This distinction is particularly important for HAAs because HAA5 is a defined regulatory group. A result for one individual HAA does not automatically demonstrate identical performance for every other HAA.
Frequently Asked Questions
What is HAA5?
HAA5 is the federally regulated group consisting of monochloroacetic, dichloroacetic, trichloroacetic, monobromoacetic, and dibromoacetic acids.
What is EPA's limit for HAA5 in drinking water?
The current EPA maximum contaminant level is 0.060 mg/L, equivalent to 60 µg/L or 60 ppb.
Does Black Berkey® reduce HAA5?
Independent testing reported Total HAA5 at 50 µg/L before filtration and below 1 µg/L after filtration, reported as greater than 98% reduction under the documented test conditions. Review the original laboratory evidence on our Berkey® Filter Test Results page.
Does every activated carbon filter remove HAA5?
No. Performance depends on the media, design, flow, contact time, water chemistry, filter condition, and other factors. Look for contaminant-specific testing for the exact filter you plan to use.
Where can I find HAA5 in my water report?
Look in your Consumer Confidence Report under regulated contaminants, disinfection byproducts, HAA5, haloacetic acids, or total haloacetic acids.
Final Thoughts
Haloacetic acids are disinfection byproducts that can form during public water treatment. For homeowners, the best first step is to find HAA5 in the local Consumer Confidence Report and understand the reported concentration in relation to EPA's current 60 µg/L MCL.
If you decide to use a filter, choose it based on documented performance for HAA5 or the individual haloacetic acids that matter to your concern. Black Berkey® Elements have independent HAA5 test evidence, whereas current Phoenix evidence should be evaluated on an analyte-by-analyte basis using the published laboratory reports.
Start with the water data, then compare the evidence for the exact filter element you use. That approach is more useful than assuming that every activated-carbon, reverse-osmosis, or gravity-fed filter performs the same way.