What Is TDS?

TDS stands for total dissolved solids in water. But what do they have to do with our drinking water quality? Find the answers to your questions.

Did you know that around 60 percent of the human body is made of water? Water is crucial for the function of our bodies and our well-being. Among many other things, water lubricates our joints, regulates our body temperature, and prevents kidney damage.

While it’s good to focus on the quantity of water we’re drinking day to day, it’s also important not to forget its quality. One measurement that’s unknown to many people is total dissolved solids or TDS in water.

Read on to learn the significance of TDS and how testing the level of TDS can help you determine the quality of your water!

What are Total Dissolved Solids in Water?

Water is called a universal solvent because it’s able to dissolve and absorb molecules from many different substances.

TDS is defined as the combined content of all inorganic and organic substances contained in a liquid that are present in a molecular, ionized or microgranular suspended form.

In other words, it's all of the minerals, salts, and organic particles in the water that you can't see.

Not all of these organic compounds are harmful, and many are naturally present in our environment. Some of these minerals include potassium, calcium, magnesium, chlorides, bicarbonates, and sulfates.

However, they can be harmful if you take in more than your body needs, or if heavy metals such as iron are present.

TDS in our water supplies can come from:

  • natural water sources
  • sewage
  • urban run-off
  • industrial wastewater
  • chemicals during water treatment
  • pipes and pipe fittings
  • stormwater
  • agricultural run-off
  • road de-icing salts


Importance of Measuring TDS

One reason it's important to test the level of TDS in your water is because high levels can give your water a bitter, salty, or sulfuric taste or odor, while low levels of TDS give your water a flat taste. The test gives you an indication of the general quality of your water.

Although high levels of TDS won’t necessarily affect your health, they can act as a warning for further investigation. For instance, readings of 500 parts-per-million (PPM) will require investigation to ensure that there aren’t toxic substances such as lead or copper affecting your water.

Levels of 1000 PPM or higher are generally considered unsafe for human consumption. If your measurement is substantially higher than 500 PPM, you should consider installing a water treatment or filtration system to lower the levels.

Measuring the level of your TDS also helps:

  • Filter maintenance: By routinely testing your TDS, you’re also ensuring that your water filter is working properly.
  • Plumbing and appliances: High levels of dissolved calcium and magnesium cause high TDS levels and hard water, which creates buildup and could eventually lead to costly pipe replacements.
  • Pools: Hard water from high TDS will also lead to clogged pipes for your pool.
  • Cooking: Cooking with high TDS will change the taste of your food. However, levels below 1,000 ppm shouldn’t affect your health.
  • Cleaning: High TDS can fade your clothes in the wash, cause buildup in your faucets, and result in water spots on your dishes.

How to Measure TDS

The easiest way to test your water is to purchase a TDS meter, which usually costs less than $20. Some filtration systems have TDS meters built in, so check for that if you have such a system.

Another way to determine the level of your TDS is to request a report from your water supplier, though the report won’t contain the reason why your TDS is high.

When you test your TDS, you’re looking for a measurement that’s 500 PPM or less, the recommended maximum amount safe for drinking as determined by the EPA.

Measuring your TDS is as easy as submersing the tester’s probes into a cup of tap water and waiting for the results.

The following table gives you a rough idea of the quality of your water according to its TDS level. Note that having a TDS level that's too low can be undesirable because the water wouldn't contain any of the minerals that are beneficial for our bodies.


0-50 PPM — Questionable

51-150 PPM — Excellent

151-500 PPM — Good

501-1000 PPM — Questionable

1001-higher PPM — Unacceptable

How to Reduce TDS

The following two filter systems are recommended for lowering the TDS level in your water. There are other effective filtering systems on the market as well, so make sure to do enough research to find the best solution for you.

  • Reverse Osmosis (RO) System: This is one of the most effective filters. It forces water through a semipermeable membrane that effectively eliminates most total dissolved solids.
  • Deionization (DI) System: Referred to as high purity filters, these systems utilize resins to control the electrical charge of ions and remove TDS through ion exchange.

Reverse Osmosis System Cost

The cost of reverse osmosis systems vary depending on size, filtration process, brand, and additional features, such as pumps, remineralization stages, and modular designs.

A standard under-sink RO system can cost anywhere from $150 to $500 USD, while some countertop units are available for less than $100. Whole house systems need to be plumbed in and may call for professional plumbers or contractors to install. These systems can cost well over $500.

Water Treatment in Your City

Now that you know the risks involved with high TDS and how to measure your own water quality, you may still be concerned even after testing your water. But nearly every utility company follows these common steps to ensure your water is safe for drinking:

  1. Coagulation and Flocculation - Chemicals are added to the water that brings together dirt and dissolved particles, creating larger particles called floc.
  2. Sedimentation – Because these larger floc particles are heavy, they settle to the bottom of the tank.
  3. Filtration - The clear water on top passes through filters of sand, gravel, and charcoal. Dissolved particles such as dust, parasites, bacteria, viruses, and chemicals are removed with these filters.
  4. Disinfection - As the last step, chlorine or chloramine is added to the water to kill parasites, bacteria, viruses, and germs. Fluorine is sometimes added to prevent tooth decay.

Depending on where you’re located, other minerals and chemicals may be added to adjust water hardness and pH levels or prevent corrosion.

Lead in Your Water

Old lead pipes and fittings are the main cause of water crises in Flint, Baltimore and other cities in the United States. Today, most pipes are made out of copper.

Lead can’t be detected by a TDS meter, but you can buy different test kits that measure lead in water. You can also have your water tested by a certified laboratory.

If you find high levels of lead in your drinking water, the Centers for Disease Control & Prevention (CDC) recommend you take the following actions:

  • Install a reverse-osmosis or other filtering system designed to remove lead from water in your home.
  • Don’t use hot tap water to cook, make drinks, or mix baby formula, as it’s more likely to contain higher levels of lead than cold water. Instead, draw water from the cold side, then heat the water yourself.
  • If you’ve been out of town, flush the pipes by running water for a minute or so. To avoid wasting water, you can take a shower to flush the pipes because human skin can’t absorb lead in water.

Pure Drinking Water for Your Family

We hope this article has given you the tools and information needed to ensure clean drinking water for your family. Measuring the total dissolved solids in your water may seem like an extra hassle, but it’s a quick and simple way to determine your water quality and attain peace of mind.

If you’d like more clear, simple-to-understand water quality information to improve your family’s health, keep reading the WaterZen blog!

In this post: TDS, total dissolved solids, TDS in water