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Shortlist

Contaminant

Chlorine in drinking water

Added by utilities to disinfect on the way to your tap, and the source of that pool-like taste and smell.

This page can’t tell you what’s in your tap water.
Only a test of water from your own tap can. Public-system results describe the system, not your home.
7 sources
01Check your water systemWater Check · system results, not your tap02Test your tapHow to get a reliable result03Treatment approachesWhat can reduce it at the tap
On this page · 10 sections
  1. 01Reference values
  2. 02Is it in my water?
  3. 03Where it comes from
  4. 04Testing
  5. 05Water filters
  6. 06Treatment
  7. 07Evidence
  8. 08Next steps
  9. 09Ask about chlorine
  10. 10References
Reference values

A ceiling on a disinfectant added on purpose.

Each value says what kind of reference it is, and they mean different things. A lower or missing number never means water is safe.

Disinfectant limit · MRDLFederal · public water systems
4 ppm

A ceiling on a disinfectant utilities add on purpose to keep water safe in the pipes.

Applies to
Disinfectant in water a public system delivers
Status
In force
Source
EPA MRDL (4.0 mg/L) · 40 CFR §141.65
Health-based goal · MRDLGFederal · not enforceable
4 ppm

The disinfectant level below which no known health risk is expected. A goal, not a limit.

Applies to
Set alongside the rule as a public-health goal
Status
Published goal
Source
EPA National Primary Drinking Water Regulations — MRDLG 4 mg/L · 40 CFR §141.53
Your stateNot held yetStates may set their own references. We don’t hold a state reference for chlorine yet.
Is it in my water?

Only a test of your own tap can tell.

Choose what you have. We’ll show what it can and can’t tell you.

If you haven’t tested
Nobody can tell without a measurement, including us.

Three things you can do, in this order.

Test water from your tapThis is the only way to know your level. Testing guidance ↓See what your system reportsSystem results aren’t a tap measurement. Open Water Check →On a private well?Public-system reports don’t cover wells. Open Well Water →
Where it comes from

Where it comes from

  1. Added to tap water by utilities to kill germs and make water safe to drink
  2. Used as a disinfectant in emergency water supplies following disasters or contamination events
Why it matters
At higher levels, chlorine can cause unpleasant taste that discourages water consumption
Low levels of chlorine in tap water kill harmful germs and prevent waterborne disease · Disinfection byproducts formed when chlorine contacts dirt or other materials in water can cause health problems at high enough levels
Testing

How to test your tap water for chlorine

Chlorine residual can be tested using a diethyl paraphenylene diamine (DPD) indicator test with a comparator, where a tablet is added to a water sample and the resulting color is compared to a standard chart to determine chlorine concentration.

  1. 01Use a certified labA state-certified lab, or a kit that sends samples to one.
  2. 02Follow the sampling stepsHow and when you collect the water changes the result.
  3. 03Check the reportIt should state units and the detection limit.
Certified labNot sponsored
Use a state-certified labYour state keeps a list of labs certified for drinking water.

Choosing a filter for chlorine

None qualify
No products currently qualify for a chlorine pick here.

Nothing in our database has a chlorine claim for an exact configuration we can verify.

Find a fit in FinderRead treatment approaches
Treatment

How to reduce chlorine in water

Function: ReduceChlorine destroys the membrane of many microorganisms and kills them, but requires direct contact with the organisms and sufficient contact time to be effective.
How to reduce chlorineChlorine is the easiest contaminant to reduce. Almost any activated-carbon filter handles it, from a pitcher to an under-sink unit. Look for NSF/ANSI 42, the standard for taste, odor and chlorine reduction.
Whole-house systems and point-of-use filters treat different water. A whole-house system treats water where it enters the home; a point-of-use filter treats the tap it’s installed on. Check which one a claim is for.
Evidence

What the evidence means

We keep evidence types apart. A result for one configuration never stands in for another, and we never average across types.

No product in our database holds a reduction record for chlorine yet.

How we read evidence →

Next steps

Take the next step

Match a system to your homeFinder asks about your home first. It suggests chlorine as a starting point, and nothing counts until you confirm it.
Ask about chlorine

Still have a question?

Answers come only from WaterDecoder’s reviewed sources and show citations. Ask can’t interpret your test result or choose a product. Don’t include personal details.

AI assistant

Ask about Chlorine

Answers draw on cited public-health sources and the filters certified to reduce Chlorine. Every source is linked, and if the sources don’t cover a question, the answer says so.

Questions to start with

Educational information from cited sources. Not medical or professional advice.

References

Where these facts come from

  1. 1Regulatory reference40 CFR §141.65EPA MRDL (4.0 mg/L)
  2. 2Regulatory reference40 CFR §141.53EPA National Primary Drinking Water Regulations — MRDLG 4 mg/L
  3. 3Knowledge BaseSecondary Drinking Water Standards: Guidance for Nuisance ChemicalsU.S. EPA
  4. 4Knowledge BaseMeasuring Chlorine Levels in Water SupplyWHO
  5. 5Knowledge BaseAbout Water Disinfection with Chlorine and ChloramineCDC (Drinking Water program)
  6. 6Knowledge BaseToxicological Profile for ChlorineATSDR (Agency for Toxic Substances and Disease Registry / CDC)
  7. 7Knowledge BaseOverview of Drinking Water Treatment TechnologiesUS EPA (SDWA program)

Written and maintained by WaterDecoder. A review date appears only once we have confirmed one.

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