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 is TDS?

If you read the acronym “TDS” and immediately thought of The Daily Show or “touchdowns scored” or “Tonga Defence Services,” then you're about to have some science dropped on you. (Or however the kids are saying it these days.)

TDS, when it comes to measuring water quality, stands for “Total Dissolved Solids” and refers to the total weight of organic and inorganic solids dissolved in a certain volume of water.

Solids that get dissolved in water include metals, salts, and minerals such as calcium bicarbonate, nitrogen, iron phosphorus, sulfur, and others. They find their way into our water supplies from several main sources:

  • Agricultural and residential runoff
  • Clay-rich mountain water runoff
  • Fertilizers and pesticides
  • Industrial waste
  • Sewage
  • Metal flake-off from pipes
  • Weathering and dissolution of rocks and soil

There are also solids that don't qualify as TDS because they don't dissolve in water but get suspended inside it instead, like wood pulp for example. Scientists call these tiny particles TSS or “Total Suspended Solids,” but that's a subject for a different article.

What are 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 micro-granular 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

How Do You Measure TDS?

The only way to measure TDS with 100% accuracy is to evaporate all of the water and measure how much solid stuff is left. Scientists call this “gravimetric analysis,” but it takes far too long for everyday purposes and is almost as boring to watch as The English Patient.

But, never fear, there's a quicker, more exciting method of measurement. (Spoiler alert: it involves TDS meters and TDS testers.)

All elements dissolved in water have either a positive or negative electrical charge. The positively charged solids are called “cations,” while those with a negative charge answer to the name of “anions.” (Be careful of “anion breath” after drinking negatively-charged water. Be careful of bad science puns too!)

This means that all water, except for absolutely pure, particle-free water, has some amount of conductivity, thanks to the TDS swimming around in there. This electrical conductivity or EC (yes, we love our acronyms around here) can be measured by passing an electrical current through the water.

That EC number can then be used to estimate the amount of TDS in the water. While this method is not quite as accurate as the boring evaporation way, it's close enough to provide a good snapshot of the quality of your water. Plus, it's much quicker and easier.

So, What's a Good TDS Level? And a Bad One?

If only there was a handy table that could answer this question. Oh, wait...

TDS Water Quality Table

Depending on the PPM number your TDS meter spits out, you would then know whether you can sit back and relax with an ice-cold glass of water, or rush outside and dig a well in your backyard. Or buy bottled water at Costco, which might be a bit easier.

The table above applies to human beings, but animals have different tolerances to high TDS levels. Here are a few examples that are pretty interesting but, admittedly, not super practical:

TDS Water Quality Table for Animals

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.

Why Should You Test the TDS in Your Water?

The first two reasons listed below are pretty obvious, but you may find the rest of the list a bit surprising. No peeking ahead!

  • Health: Higher TDS levels are usually the result of non-toxic substances such as potassium, chlorides, and sodium. But there may also be toxic ions present, including arsenic, cadmium, and nitrates. And hey, even if the particles aren't poisonous, you still don't want a lot of them in the water you drink.
  • Taste: While a small amount of TDS can improve the taste of water, too many of them, or the wrong kinds, can make water taste salty, bitter, or metallic. If we want to drink weak-tasting liquid, we'll stick with diet soda!
  • Filter Efficiency: Testing your water with a TDS meter can let you know if your filter is working properly or not. Filters certainly aren't going to tell you when they need to be replaced.
  • Water Hardness: A high TDS level can signal that you have hard water, which can cause gunky buildup in pipes and valves, weaken their performance, and add to maintenance costs. (Also, we love using the word “gunky.”)

Special note: Hard water doesn't necessarily have high TDS levels. Water softeners replace the magnesium and calcium ions that cause hard water with sodium or potassium ions. The resulting soft water could have even more TDS than the hard water did. Crazy, huh?

  • Aquaculture: The TDS level of the water in an aquarium should stay constant and be the same as the original habitat of the fish and sea life living inside.
  • Pools and Spas: Proper maintenance of any pool or hot tub should include continual monitoring of TDS levels. Too much or too little chlorine solution can make your swims uncomfortable or unsanitary.
  • Hydroponics: In case your profession or hobby is growing plants outside of dirt, testing the TDS level of your hydroponic solution is the best measurement of its nutrient concentration.
  • Commercial/Industrial: Testing TDS levels in water may be more critical for a farm-fishing company than, say, an accounting firm, but the above principles are still helpful for many industries out there.

TDS Meters

Yep. And TDS testers as well. Like Superman and Clark Kent, TDS meters and TDS testers are the same thing with a different name.

TDS meters/testers function like an ohmmeter by zapping a tiny current through the water, measuring the voltage, and then calculating the EC. That EC amount is then multiplied by a number between 0.50 and 1.00 (depending on the types of TDS) to come up with the TDS level.


How's that for some science at work?

TDS meters/testers make measurements in milligrams of TDS per liter of water. Since there are 1 million milligrams in a liter, it's also called parts-per-million or PPM. (This acronym got us in trouble with the National Anti-Acronym Association or NAAA.)

How to Reduce TDS

So, you used your TDS meter/tester and discovered that your water has a higher level than you'd like. Now what? How do you get those invisible TDS out of there? Asking them nicely probably won't work.

Luckily, there are several other ways to reduce or even eliminate the TDS from your water:

  • Carbon filtration: The downside to this method is that it yields only a slight reduction in TDS levels.
  • Deionization: No, this doesn't mean turning someone into Deion Sanders. Instead, it's the process of adding a final polishing filter to a reverse-osmosis filtration system (see below).
  • Distillation: This results in total-particle reduction (sounds like something from Ghostbusters or Star Trek), leaving the water with a flat taste.
  • Reverse Osmosis: This type of filtration achieves near-total TDS elimination, but leaves just enough to give the water a nice taste.

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.

What Should You Do Now?

So, now that you're armed with more knowledge about TDS than you ever thought you'd have, we at WaterZen encourage you to purchase a TDS meter and test your drinking water. For more info on TDS meters/testers, click here.

If it turns out your water's TDS level is higher than you're comfortable with, or higher than even the EPA is comfortable with, there are steps you can take to protect your family and community:

  • Use one of the filtration methods listed above to clean your water
  • Buy bottled water for drinking and cooking
  • Report your findings to your local city government or water authority
  • Let your neighbors know or even contact the local press

At the very least, you can talk about TDS, EC, and PPM at a dinner party and sound like the smartest person in the room. You're welcome!

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!

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