What Is TDS & Why TDS is a Bad Measure of Drinking Water Quality
Picture this: News just broke about a widespread lead contamination problem in your city. Haunted by the dark memories of the Flint water crisis, you begin scouring the internet, desperately trying to find a way to check if your water has been affected. Moments later, you come across something called a TDS meter, a device the vendor says you can use to evaluate your water quality in seconds. Without thinking twice, you order it and pick it up at the store the next day. After performing the TDS test, the results show that your water is safe and contaminant-free. Still, the water appears cloudy and has a rusty orange look. It also tastes metallic and bitter and has a rotten egg scent. How is this possible?
The problem is that TDS is not a good measure of water quality – although many water filtration companies use high TDS as an argument for water filtration. TDS meters do not detect specific contaminants in water, nor do they give meaningful information about most water pollutants. There are several reasons for this, but before we get into that, let’s define TDS then work our way back.
What is TDS, and how is it measured?
TDS, short for Total Dissolved Solids, is a measure of the combined total of organic and inorganic substances dissolved in water. TDS is expressed in milligrams per liter (mg/L) or parts per million (ppm) and includes anything present in the water other than the pure H2O molecules. The main constituents are usually calcium, sodium, magnesium, and potassium cations (negatively charged ions) and carbonate, hydrogen carbonate, chloride, sulfate, and nitrate anions (positively charged ions).
TDS in water typically originate from various sources, including:
- natural sources, such as mineral springs, salt deposits, seawater intrusion, and carbonate deposits
- urban and agricultural run-off
- sewage and industrial wastewater discharges
- chemicals used to treat water
- the hardware or piping used to distribute water to your home
- salts used for road de-icing
- anti-skid materials, and others
Testing your water with a TDS meter is the quickest and most convenient way to measure the water’s TDS level. Since salts, minerals, and other dissolved ionized solids increase the conductivity of a liquid, a TDS meter measures the solution’s electrical conductivity then uses that reading to estimate the TDS.
What is a good or bad TDS level?
Since TDS in water does not pose a health risk, the EPA has not identified a TDS limit. However, the agency suggests that drinking water contains no more than 500 ppm of TDS. Any value higher than is said to cause noticeable deposits in the water, heavier or salty taste, staining, etc.
Here’s a TDS water chart to illustrate the various TDS levels in water and their respective ratings:
Level of TDS (mg/L) Rating
Less than 50 Considered low: Missing some vital, healthy minerals
50 – 300 Excellent: The perfect level for TDS in drinking water
300 – 500 Good: The sweet spot for TDS in drinking water
600 – 900 Fair: Consider a reverse osmosis system to remove your TDS
900 – 1200 Poor: Not recommended or safe for use
Above 1200 Unacceptable: Completely unsafe and possibly too much to handle for household filters
My tap water has an excellent TDS level. Does that mean it is safe to drink?
The answer is no. TDS is just an aggregate measure of the charged compounds in water. Uncharged contaminants like pesticides, gasoline, motor oil, and pharmaceuticals do not contribute to a TDS measurement. Also, TDS meters do not detect PFAS in drinking water. That means a TDS meter may indicate that your water has an excellent TDS rating – causing people to believe that their water is safe — while the water is still contaminated with all kinds of toxic pollutants.
It’s also worth noting that even though some toxic contaminants are charged when dissolved in water, a TDS meter does not provide meaningful information about the contaminants’ presence and concentration. That’s mainly because:
- A TDS tester is not sensitive enough to detect and measure toxic levels of arsenic, lead, chromium-6, and other harmful pollutants, even if they are present the water. Usually, cheap TDS meters display readings on parts per million, while contaminants like lead, arsenic, and chromium-6 are harmful at parts per billion concentrations, which is a thousand times lower.
- A TDS meter cannot differentiate among different ions. TDS meters are non-selective. Because of this, a more advanced piece of technology is required to measure some water contaminants.
We’d hate to sound like a broken record, but we must reiterate that lead and arsenic measurements cannot be made using a TDS meter. Instead, they must be evaluated using much more sophisticated testing equipment. People often get tricked into thinking that their water quality is pristine or “not so bad” after finding its TDS level, but TDS meters are known to draw false conclusions about water quality. A water sample may have lead levels 100 times the EPA limit, and the TDS reading falls between 000 and 001. That’s why you simply cannot judge how clean your water is by measuring its TDS.
Then why do water filtration companies promote TDS as a strong reason to filter your drinking water?
Customers are always searching for affordable and effective solutions – and most companies are aware of that. Since TDS meters are cheap, user-friendly, and allow anyone to test their water in seconds, many water filtration companies promote high TDS as a bad thing to persuade people to filter their drinking water. They also use it to attract more customers and increase sales.
So, should I purchase a TDS meter to test my tap water?
No. There’s no need to drink water considerably low TDS or deionized water. If you are concerned about your water quality, put your money towards purchasing an effective and reliable drinking water filter from Springwell that removes harmful contaminants from your water.
What if I already have a TDS meter?
If you have a TDS meter, we recommend giving it to a child interested in science. Use it to teach them about dissolved minerals by encouraging them to test water from different sources (river, lake, distiller, rain, sea) and try to interpret their findings.
What testing method can I use to get accurate results about my water quality?
If you want to measure your water quality accurately, there are several alternative methods other than TDS. These methods include:
- A water quality testing kit: The quickest and most inexpensive water testing method is a home water testing kit. A good-quality water testing kit can give you a clear insight into the quality of your drinking water and specific contaminants that are potentially present. Even better, the test can be performed in a few minutes.
- A water quality report: Another way to determine your water quality is to contact your local water provider and request a copy of their latest water quality report. Every water provider must provide customers with an annual water quality report (aka, a Consumer Confidence Report). This report may be available online and typically contains detailed information about the levels of certain chemicals and other pollutants in the water.
- Laboratory testing: If you’re looking for a more extensive and accurate testing method, your best option is to send a water sample from your tap to a local laboratory. While this method provides the most accurate results, be prepared to shell out a “decent” amount of cash, and wait to receive the results in about a week or two.
My drinking water is contaminated. What do I do?
If your water tests negative for specific contaminants from any of the methods above, that’s awesome! But if the test results give you a scare, we’ve got you covered. Springwell’s premium whole house filters and reverse osmosis systems selectively filter harmful materials from your water (like copper, lead, chromium-6, pesticides, pharmaceuticals, disinfection byproducts, and things that make water taste and smell bad (chlorine, chloramine, sulfur). Our filtration systems don’t remove minerals like calcium and magnesium, except for our top-tier water softeners that remove high amounts of calcium, magnesium, and other hard-causing minerals to “soften” water. If you’re looking for something specific, don’t hesitate to contact us, so we can help you find a filtration system that best fits your situation and your specific needs.
Final Thoughts
Knowing what’s in your water is very important. But think twice before using TDS to evaluate your water quality. Instead, complement it with other technologies or use a more advanced testing method, such as a DIY water testing kit. You can also contact your local water provider and ask for their most recent water quality report, or bring a water sample to a laboratory near you.
