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What is TDS in water and why it matters for what you drink

TDS stands for ‘total dissolved solids’ – a measure of all the substances hiding in your water, good and bad. These can include pollutants, microbial pathogens, heavy metals, and mineral compounds that make their way to your tap.

While it’s natural for water to contain some level of TDS, higher levels can impact the taste, odor, and appearance of your water, and may even contribute to issues like dry skin and hair.

Your TDS level can vary depending on where you live. Use the tool on the right to enter your zip code and see what’s in your water.

Enter your zip code to retrieve your area's average TDS reading.

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TDS

By understanding your TDS levels, you can better assess water quality and choose the right filtration system for your needs.

Where do dissolved solids come from?

Dissolved solids are a measurement of compounds like minerals, salts and organic compounds that are dissolved into water through contact with rock and other surfaces. TDS can be made up of several different types of compounds (including but not limited to): calcium, magnesium, iron, sodium chloride and sulfides (which are compounds frequently found in groundwater supplies).

  • Wastewater and Contamination

    Industrial waste, mining runoff, and water pipe erosion contribute to water pollution, introducing harmful substances and elevated total dissolved solids (TDS)

  • Environmental Disruptions

    Decomposing algae, plants, and deceased animals release organic matter into water, increasing total dissolved solids (TDS). Effective water treatment is essential to maintain quality and safety.

  • Human Activities

    Human activities, such as industrial discharges, agriculture, and urban runoff, contribute to elevated total dissolved solids (TDS) levels in water bodies, impacting aquatic ecosystems and necessitating water quality management.

  • Natural Sources

    Minerals, salts, and ions from natural sources like rivers and groundwater contribute to total dissolved solids (TDS) in drinking water, influencing taste and quality. Monitoring and treatment ensure potable water.

Is high TDS water harmful?

Not necessarily. A high Total Dissolved Solids (TDS) reading doesn’t automatically mean your water is unsafe. It simply reflects how much dissolved material is present. In many cases, elevated TDS comes from harmless minerals like calcium or magnesium.

The EPA’s secondary (non-enforceable) guideline for TDS is 500 mg/L, which is based on taste, odor, and appearance—not health risk. The key issue is what makes up those dissolved solids. Potentially harmful contaminants like lead, PFAS, or certain pharmaceuticals can be present at very low levels and may not significantly impact a TDS reading at all.

This is why a TDS meter is useful for measuring changes in water quality and confirming filtration performance—but it doesn’t identify specific contaminants or guarantee safety on its own.

To better understand contaminants that may not show up in TDS readings:

Learn about PFAS in your water

TDS measures the total amount of dissolved substances in water, but does not identify specific contaminants or their health effects.

woman wearing ring testing water in glass with total dissolved solids meter

Real-time filtration proof

Every Culligan with ZeroWater Technology water filter pitcher and dispenser includes an electronic TDS meter to measure the level of total dissolved solids in your water. Our 5-stage filtration technology removes 99.9% of total dissolved solids from your water – guaranteed.

Drink with confidence

With our real-time integrated electronic meter, you'll always know your filter is working to remove dissolved solids and when it’s time to replace your filter. If your water has higher TDS, you'll need to replace your filter more often. But that’s a sign your filter is doing its job, removing more dissolved solids from your water.

How to test your water

Before placing the TDS meter into your new device, try it on your tap water first to see the difference.

  • Step 1

    Start with your tap water. Insert the base of the meter into your water, and uncover what’s really there.

  • Step 2

    Test your old pitcher or dispenser.

  • Step 3

    Then test your Culligan with ZeroWater Technology filter – enjoy water with zero dissolved solids, guaranteed.

When to replace your filter

Your filter’s lifespan will vary based on the TDS level of the water you’re filtering. Here is a breakdown of TDS ranges and their projected filter lifespan.

Pitchers and Dispensers

Reduce 99.9% of TDS using Culligan with ZeroWater Technology

7 Cup Pitcher 7 Cup Pitcher - Hover
ZeroWater Technology

7 Cup Pitcher

Easily fits in your fridge door
10 Cup Pitcher 10 Cup Pitcher - Hover
ZeroWater Technology

10 Cup Pitcher

Fits most fridge shelves
12 Cup Pitcher 12 Cup Pitcher - Hover
ZeroWater Technology

12 Cup Pitcher

Fridge-friendly capacity
22 Cup Dispenser 22 Cup Dispenser - Hover
ZeroWater Technology

22 Cup Dispenser

A whole day’s supply
32 Cup Dispenser 32 Cup Dispenser - Hover
ZeroWater Technology

32 Cup Dispenser

For the entire family
40 Cup Glass Dispenser 40 Cup Glass Dispenser - Hover
ZeroWater Technology

40 Cup Glass Dispenser

A hosting must-have

Filter Life

Filter life can vary because TDS levels differ by location. Use the zip code finder at the top of this page to check the average TDS levels in your area.

If your meter reads 6 or higher within the first month, check that your device is assembled correctly following the installation and operating instructions manual. Ensure the filter is securely locked in place, and always pat the TDS meter completely dry before reinserting it into your device. When installing a new filter, rinse the outer shell for 30 seconds.

You’ll know it’s time to change your filter when the orange light comes on and the meter reads 6 or higher.

TDS Meter - General

A TDS meter is an electronic device that measures the level of total dissolved solids (TDS) in your water, in parts per million (ppm). TDS can refer to all organic and inorganic materials, such as metals, minerals, salts and ions dissolved in your water. TDS can affect the taste and appearance of water.

Our integrated electronic meter gives you instant confirmation that your filter is reducing dissolved solids and signals when a new filter is required. A reading of 0 means your filter is removing virtually all dissolved solids; once the orange light appears and the meter reads 6 or higher, it’s time to replace the filter.

The orange light is an indicator that your filter is nearing the end of its life. Specifically, it turns on when the meter detects a reading of 6 or higher, signaling that dissolved solids are no longer being effectively removed and it’s time to replace the filter.

TDS Meter Readings

If your meter does not read “0”, check that your device is assembled according to the manual:

  1. Ensure you thoroughly rinse and dry your new filter.
  2. Make sure the filter is locked securely in place. You should hear a slight click.
  3. Pat the TDS meter and the docking station completely dry before reinserting it.
  4. When installing a new filter, rinse the outer shell for 30 seconds.

Great question! There are a variety of reasons why your TDS readings might vary. TDS meters are super sensitive, so even small things—like the temperature of the water or fingerprints on the glass—can affect the results. To get the most accurate reading, be sure to rinse and dry both the glass and the pitcher or dispenser before you start filtering. A quick clean goes a long way!

The wave screen means that the TDS meter is in the process of measuring the level of total dissolved solids in your water. If the wave continues for longer than 10 seconds, ensure the batteries have sufficient power, that the receiver on the meter is dry, and that the device is properly assembled and cleaned.