How to Test for Hydrogen Sulfide in Well Water
Number copied. Text it from your phone: 443-277-2204.
Start with your nose, then get a number from a test made for hydrogen sulfide (H₂S), the gas that makes well water smell like rotten eggs. Smell the cold tap and the hot tap after the water has sat in the pipes for a few hours. If the cold water smells too, at every tap, the gas is usually coming from the well.
To find out how much is in the water, test it right at the tap with a hydrogen sulfide test strip or color-matching kit, or send a lab a sample that is preserved the moment you collect it. An ordinary mailed water test misses the gas, and that includes our $199 well water test, which measures sulfate, not hydrogen sulfide.
One caller put it this way: "I've got the smell of sulfur, but I don't know where to get that tested or how to get that tested." This page answers both.
Quick Answer
Hydrogen sulfide testing is uniquely difficult because the gas escapes your water sample within minutes. So you test it at the tap, or the lab sample is preserved when you collect it.
- Test at the tap. A WaterWorks hydrogen sulfide strip reads up to 2 ppm in 20 seconds. Hach's HS-C color-matching kit reads up to 5 ppm in about 2 minutes. See what each test reads and how to run one.
- A mailed sample needs a preservative. In a plain bottle the gas escapes before the lab tests it. Our $139 hydrogen sulfide lab test uses a preserved sample and reads down to 0.1 ppm. See getting a lab number.
- Your nose comes first. If you can smell rotten eggs, you already have at least 0.05 ppm H₂S. A true rotten egg smell, not just musty, usually means 1 ppm or more. A smell in the hot water only usually means the water heater. See the smell test.
- The number picks the fix. The treatment changes at about 1 ppm and again above 10 ppm. A strip that stops at 2 ppm cannot tell 3 ppm from 30.
What's in This Guide
Start with a free smell test
Smell the water before you buy any test. It costs nothing and shows where the gas is coming from. Do it like this:
- Wait until the water has sat in the pipes for a few hours: first thing in the morning, or after you have been out.
- Run a glass from the kitchen cold tap, step away from the sink and smell it.
- Do the same with the hot tap.
- Repeat at a bathroom sink at the other end of the house.
| What smells | Where it usually comes from | What to do next |
|---|---|---|
| Hot water only | A metal rod inside the water heater (the anode rod) | No water test needed. A plumber swaps the rod for an aluminum or zinc one, then disinfects the tank with bleach. See hot water smells like rotten eggs. |
| Cold and hot, at every tap (the hot may smell stronger) | The well water | Get a hydrogen sulfide test. See what each test reads. |
| Softened water only, not untreated water | Bacteria growing in the softener | Turn the softener's bypass valve, then smell the cold tap. See does a water softener remove sulfur smell. |
| One sink only | That sink's drain | Clean that drain. The water itself is not the problem. See where the rotten egg smell comes from. |
Your nose also gives you a rough level. The World Health Organization puts the taste and smell threshold for hydrogen sulfide in water at 0.05 to 0.1 ppm, below the lowest step on the common WaterWorks strip (0.3 ppm). Connecticut's health department and the University of Georgia's water lab both describe a musty or swampy smell under about 1 ppm and a true rotten egg smell from about 1 ppm up. What each level does to your pipes is in what your hydrogen sulfide level means.
I usually ask callers the same first question: "Do you smell it on the cold or the hot or both?" It is at 0:34 in this video.
What each hydrogen sulfide test reads
Choose a test by the levels it can read. The common strip stops at 2 ppm (parts per million), a color-matching kit reads to 5 or 10 ppm, and our lab test reports from 0.1 ppm up. The ranges, times and prices below are from each maker's own listing, read in October 2026.
| Test | What it reads | Time | Price |
|---|---|---|---|
| Basic test strip (WaterWorks, SenSafe part 481167) | Up to 2 ppm (starts at 0.3) | 20 seconds | $16.99 for 30 tests |
| Low-level test kit (SenSafe Quick Ultra-Low, part 481201) | Very low levels, up to 1 ppm | 2 to 5 minutes | $52.99 for 50 tests |
| Color-matching kit (Hach HS-C) | Up to 5 ppm | About 2 minutes | $116 for 50 tests |
| Color-matching kit (CHEMetrics K-9510) | Up to 10 ppm | 5 minutes | Not listed on the maker's page |
| Mailed lab test (our hydrogen sulfide lab test) | Hydrogen sulfide from 0.1 ppm up, plus pH | About 10 business days | $139, prepaid return label |
If the cold water smells and you want a quick number, a strip is a fair place to start. Callers ask me about the home test kits at Lowe's and Home Depot, and the ones that actually test for hydrogen sulfide are pretty accurate; we have tested them against our dealer kits.
Two readings send you past the strip. One caller's strip read zero while his water smelled. On the WaterWorks strip, zero means the level is under its first step of 0.3 ppm, and SenSafe's ultra-low kit reads below 0.05. A strip that shows its top color, 2 ppm, means you need a test that reads higher, because the treatment changes again above 10 ppm.
Under about 1 ppm, a carbon filter can be enough for a light smell, though the carbon wears out sooner on sulfur. Up to 10 ppm, an air-injection sulfur filter with Katalox Light takes it out with no chemicals; 10 ppm is the most it is rated for. Above that, chlorine or peroxide is fed into the water and then filtered.
How to test the water at the tap
Test the water as soon as it leaves the tap. The reading drops as the gas escapes. Each kit comes with its maker's instructions; these are the steps they share.
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Skip the softener for this test
If you have a water softener or a filter, turn its bypass valve so the water you test comes straight from the well.
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Fill the cup from the cold tap
Use a clean glass for a strip. For a kit, fill its bottle or cup to the line: 100 mL for Hach's HS-C, 25 mL for the CHEMetrics kit, 50 mL for SenSafe's ultra-low kit.
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Test it right away
Do not let the water sit. SenSafe says to run the test immediately after collecting a fresh sample, and Hach's instructions say the hydrogen sulfide level drops quickly after the sample is collected.
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Follow the kit's directions
WaterWorks strip: hold it in the water for 20 seconds, moving it back and forth, then match the pad to the color chart. Hach HS-C: add the reagents, cap the bottle and set a 2 minute timer, then match the test paper to the chart. CHEMetrics: read the ampoule 5 minutes after you snap its tip.
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Write down the reading
Note the number, the date, which tap you used and whether the smell was faint or strong. Send that to me along with any lab report you already have.
Getting a lab number for hydrogen sulfide
A lab sample has to be preserved as soon as you fill the bottle. In a plain bottle the gas escapes on the way, and the report comes back low or "not detected" while your water still smells. That is why our $199 well water test does not include it: when a caller asked me why, I told him the gas would be gone by the time the sample reached the lab.
There are two ways to get a preserved sample to a lab:
- Our hydrogen sulfide lab test, $139. The kit is built for a field-preserved sample. You mail it back with the prepaid label, and an accredited lab reports dissolved sulfide and pH, usually in about 10 business days.
- A state-certified lab near you. When a caller wants it done locally, I tell them to search for a state-certified water testing lab near them and ask whether it tests for hydrogen sulfide. Get the sample bottle, the preservative and the instructions from the lab. If you want other tests too, they need a separate bottle, because the preservative interferes with them.
A report of "not detected" means below the lab's reporting limit, which is 0.1 ppm on our test. Since the nose can pick up the gas at 0.05 to 0.1 ppm, a faint smell and a "not detected" report can both be right: the level is below what the lab reports.
Text Aidan what you found
Send the number, which taps smelled and whether you have a softener. Aidan will tell you what it points to.
8 AM to 5 PM Eastern, seven days a week. A real person, not a call center.What else to test at the same time
Test your iron, manganese and pH too. The filter that takes out the gas has to handle them as well. The air-injection filter with Katalox Light handles up to 30 ppm of iron, 15 ppm of manganese and 10 ppm of hydrogen sulfide in one tank. It works best near pH 8. If yours is lower, send me your test before you order.
Our $199 well water test covers those from one sample: pH, hardness, iron, manganese and sulfate are among its 53 results. A sulfate number on that report is not your hydrogen sulfide level.
Frequently asked questions
Is it safe to drink water that contains hydrogen sulfide?
Usually, yes. At the levels found in well water it is a nuisance, not a health threat. Penn State Extension says it makes water undrinkable long before it reaches harmful levels, which is why it has no drinking water standard. Breathing the gas is different. Washington's Department of Health lists eye, nose and throat irritation even at levels that smell like rotten eggs. People with asthma may find it harder to breathe.
Is there a detector for hydrogen sulfide?
Yes, but they test the air, not your water. OSHA describes electronic meters, detector tubes and gas monitors that test the air for hydrogen sulfide. For your water, use a strip, a color-matching kit or a lab test. See what each test reads.
What is a good sulfate level for drinking water?
Under 250 mg/L. That is the EPA's guideline for sulfate. Above it, water can taste salty. Connecticut's health department adds that high sulfate can have a laxative effect, mostly a concern for infants. Sulfate has no smell, so it is not the rotten egg gas. Our $199 well water test reports it.
Aidan Walsh
Co-owner & Residential Water Treatment Specialist, Mid Atlantic WaterAidan Walsh has spent 32 years in residential water treatment, the first stretch of it installing and servicing well systems before Mid Atlantic Water became an online supplier. Mid Atlantic Water is a family company; every recommendation on this site is based on what actually failed in the field and what fixed it. If you have a question this page did not answer, call 800-460-5810 or text him at 443-277-2204.
Aidan answers calls and texts 8 AM to 5 PM Eastern, every day.Number copied. Text it from your phone: 443-277-2204.