How to Test Water Purity

Co-authored by wikiHow Staff

Last Updated: December 14, 2022 References Approved

Lab Test

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Inspection

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Strip Kit

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TDS Meter

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Video

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Tips

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Warnings

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Things You'll Need

Clean drinking water is one of the most important resources in the world. Although pollution is a scary issue to worry about, there are a few simple ways to put your water to the test. For the most accurate results possible, get in touch with a certified testing lab. If you suspect that something is wrong, inspect the water and then get a home testing kit. Also, try using a TDS meter to detect minerals in the water. Pure water means healthier, tastier water, so check your water supply at least once a year to ensure it is clean.

Method 1

Method 1 of 4:

Lab Test

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Request a water report if you get your water from a supplier. If your water comes from a city treatment plant or a utility company, expect it to be clean. Suppliers have to test the water at least once a year and often do it more than that to detect problems right away. Most companies send out a report at least once a year after you pay your bill. If they don’t, call the city or the utility company for more information.^{[1]
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- If you suspect that something is wrong, you can still send a sample into a testing lab for a second opinion.
- If you have a private water source, such as a well, you are responsible for checking the water. Test the purity at least once a year using labs or testing kits.
2
Contact a state certified laboratory to get your water tested. To find a list of labs that accept water samples, call your local health department or utilities department. Some health departments have the ability to perform the test. If that isn’t an option, try to find the closest testing lab. You may not have one near your home, but you can always mail the sample.^{[2]
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- For example, if you’re in the U.S., take advantage of the EPA’s website to find certified labs. Visit https://www.epa.gov/waterlabnetwork.
- You could also call a hotline for assistance, such as the Safe Drinking Water Hotline at 800-426-4791.
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3
Choose a reason for the test to get instructions on how to complete it. Call the lab to order a test. The lab will ask you the reason for the test, so be prepared to describe your concerns about the water quality. There are many different reasons why your water could be contaminated, so be as specific as you can in order to get the test you need. The lab will then tell you what you need to do to complete the test.^{[3]
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- Listen to the test instructions very carefully. Some tests have special requirements, and if you don’t follow them, you won’t get an accurate result. With a bacteria test, for example, you have to refrigerate the sample and take it to the lab within 2 to 3 days.
- If you’re looking for a convenient way to get a test done, ask the lab if they can send a technician to your home. The technician takes the sample for you, so you don’t even have to worry about following any instructions. Be aware of the cost, though, since it is always more than a regular test.
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Fill a sterilized container with a sample of water. To guarantee the most accurate test possible, get a sterile container from the lab. Don’t remove the cap until you’re ready to take the test. When you’re ready, dip the container into the water to fill it up. Cap it and return it to the lab as soon as possible.
- If you can’t get a container from the lab, sterilize your own. Glass is easy to sterilize by keeping it in a pot of boiling water for at least 10 minutes.
- To sterilize plastic, wash it out with a mixture of 1 cup (240 mL) of warm water and 1 US tbsp (15 mL) bleach. Rinse it off, then microwave the wet plastic for about 2 minutes. Be careful, since the plastic can melt if dries.
5
Return the sample to the laboratory for analysis. Follow the testing procedure to submit the water sample. If you live close to the lab, drop the sample off at the front desk as soon as possible. Otherwise, most labs will email you a shipping label you print out and use to get the sample there in 2 to 3 days. Then, all that is left is to wait 1 to 2 weeks for a call with your results.^{[4]
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- After you get the results, ask the lab technicians for advice on how to treat your water.
- Based on results, buy a home water filtering system or talk to someone at your water utility for more recommendations.

Method 2

Method 2 of 4:

Inspection

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Fill a clean, clear glass full of water. If you’re collecting a sample from the tap, let the water run for at least 1 minute. Then, fill the glass so it’s at least ¾ of the way full. This is more than enough to spot anything out of the ordinary in a sample.
- For pools of water, scoop up a sample with the glass. You don’t need to sterilize the glass first.
2
Hold the glass up to the light to see if it looks cloudy. Think of the crystal clear water at a beautiful beach. Clean water looks transparent and doesn’t have anything floating in it. If you can’t see your hand on the other side of the glass, you’re probably not going to enjoy drinking that water. Anything floating in the glass could be a sign of bacteria or other problems.^{[5]
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- Before getting on the phone with your water department, set the glass down and wait for a minute. Sometimes milky water clears up right away. That means the color came from air bubbles, so your water is safe to drink.
- Hard water is water that has calcium, magnesium, and other minerals in it. The minerals cause the water to look a little cloudy. It is usually safe to drink but can be fixed with a water softener to avoid damage to your plumbing.
- Treat water with colored particles. For example, brown or orange particles are from rusty pipes while black ones come from rubber. Call a plumber to fix the problem.
3
Look for color changes in the water. Even if your water doesn’t have anything floating in it, it may still not look completely clear. Discolored water not only looks gross but is a big red flag. These colors also turn up as stains on your dishes, clothing, bathtub, and other places. Use the strange coloring to figure out the source of the contamination before paying for a more comprehensive purity test.^{[6]
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- For instance, brown water is a very common problem. The contamination comes from dirt and other sediments, which you might see settle at the bottom of the glass.
- Red and orange colors come from rusty pipes. Black could mean you have lead in the water, a very toxic metal that also often comes from pipes.
- Green usually means algae grew in your water supply, so don’t drink it. If it has a blue-green coloring, it could be copper instead. A black stain could also mean mold.
4
Smell the water to see if it smells harsh or rotten. If the water smells bad, play it safe by assuming that it is going to be unsafe to drink. Sometimes water has that distinct rotten egg smell of sulfur, which comes from bacteria in the water. Other times, it could have the smell of a swimming pool because of chlorine contamination.^{[7]
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- If your water smells like nail polish or varnish, that could mean that some chemical leaked into the water supply. It might be from a home improvement project, for instance.
- Purify water by filtering and boiling it to remove contaminants. If you’re using municipal water, call your city or utility company. Contact your local government for more information.
5
Taste the water for bitterness if it looks safe to drink. If you don’t see anything unusual about the water, taste a little bit of it with the tip of your tongue. You can usually detect polluted water right away. Bitterness often means metal in the water, so order a more complete water test as you look for problems. If you detect salt instead and live near the sea, seawater could be leaking into your plumbing.^{[8]
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- Clean water has a flat, bland taste. If your sample tastes metallic or like a fizzy soda, don’t risk drinking it.
- Keep in mind that you can’t always taste water quality issues. Things like bacteria and pesticides may not be easy to detect. Normally you can tell by looking at the water, but double-check with a lab test if necessary.

Method 3

Method 3 of 4:

Strip Kit

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Purchase a water purity testing kit with reactive strips. If you have ever used these strips to test pool water, you already know how they work. The little paper strips in the kit change color according to what is in your water. There are many different types of strips available, so choose a kit that covers what you wish to test. Most tests measure everything from pH level to chemicals in the water on a single strip.
- A comprehensive testing kit covers water pH, hardness, and mineral levels. It’s a great way to detect nitrates from fertilizers and other run-off, but it may also cover lead, copper, calcium, and other things too.
- Test kits are available online and at most hardware stores. They are great when you need a quick estimate of your water’s quality, but they are nowhere near as accurate as an official lab test.
2
Fill a clean glass with a sample of water. Wash the glass out with soap and water, then fill it about ¾ of the way full. Using less water is fine as long as you have enough to cover the testing strip. If you’re taking a sample from the tap, let the water run for at least a minute before filling the glass. To collect a sample from a well or another place, use the glass to scoop up some water.
- You don’t need to sterilize the glass. As long as you clean it ahead of time, it won’t significantly affect the test.
3
Submerge the strip in the water for at least 2 seconds. Drop the strip into the water to complete the test. That is all you have to do to get it to change color, so it’s very easy. After giving it a few seconds to absorb some of the water, pull it out and set it aside on a paper towel.^{[9]
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- Most kits use multiple strips for different tests. For example, you might have a strip that tests pH, another that tests for nitrate, and a few more for bacteria and lead. You can use the same sample for each test.
- Lead and bacteria tests typically require you to soak the strip for as long as 10 minutes. Be sure to check the instructions for more information about each test!
4
Compare the test strip to the colors on the kit chart after 1 minute. After a minute of drying, the strip maintains its color. Look for a color chart included with the kit’s instruction booklet. Match the color of the strip to chart to determine what is in your water. The chart will indicate what each color means in parts per million (ppm).^{[10]
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- The strip darkens as it detects more of something in your water. When testing for nitrate, for example, the strip turns from white to purple.
- Compare the results to what safe drinking water is supposed to be like. For instance, regular water has a pH from 6.5 to 8.5 with a a nitrate level below 10 ppm. The lead level needs to be below 15 parts per billion (ppb).
- If your water quality seems low, check with your government’s local health or utility department. Consider getting a more thorough test done with a certified lab.

Method 4

Method 4 of 4:

TDS Meter

1
Use a TDS meter to detect the mineral level in water. A TDS meter detects total dissolved solids (TDS), which basically means all the stuff that is hard to spot by eye. It detects anything that conducts electricity. It’s a very quick and inexpensive way to figure out how much of your water is made up of minerals like magnesium and calcium. It doesn’t pick up bacteria, pesticides, and other contaminants.^{[11]
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- Check for TDS meters online or at your local hardware store.
- ”Hard water” means that your water has a lot of minerals in it. It’s a problem if you notice white spots from mineral stains or soap scum. Hard water can also irritate your skin or cause water heaters and clothing to break down more quickly than usual.
- TDS tests are not perfect. They don’t cover many other water problems, including pollution from pesticides or lead. Call a certified lab for a more complete test.
2
Fill a clean glass with a sample of water. Wash out the glass with soap and water before using it. Fill it about ¾ of the way full so you have plenty of room for the meter. If you’re planning on testing your tap water, simply fill it with water from the faucet. Otherwise, dip the glass into the water to collect a big sample.
- You need at least ¹⁄₂ in (1.3 cm) of water for the test, enough to submerge the tip of the meter.
- Sterilizing the glass isn’t necessary since you’re not testing for things like bacteria. It won’t affect the test.
3
Submerge the tip of the meter in the water sample. Take the TDS meter out of the box and pull the cover off of it. It’s like a thermometer and has one end that activates when you put it in the water. Turn the meter on and push that end about ¹⁄₂ in (1.3 cm) into the water. Keep it there until you see numbers appear on the meter’s screen.^{[12]
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- Don’t submerge the entire meter or else you might damage it.
4
Check the readout to figure out if your water is at a safe level. The TDS is measured in parts per million (ppi). This number changes a lot depending on where you live and what is going on with your water supply. On average, a ppi of less than 600 is considered to be good. Anything over 900 is considered to be poor, and 1,200 ppi means your water is bad news.
- If your water has a high TDS rating, treat there are several ways to treat it. The easiest way is to get a reverse osmosis water filter that draws out the solids. Another way is to distill by boiling it and collecting the water vapor.
- Keep in mind that a low TDS rating doesn’t necessarily mean your water is safe. It means that it has a low amount of solid minerals, which aren’t necessarily harmful to begin with.

Warnings

Dirty water is often very unsafe to drink, so if you suspect that something is wrong, don’t drink it until you get it tested.

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