What is TDS in Water? Total Dissolved Solids Explained

TDS is a measure of the total dissolved solids in water. Understanding TDS is important because it helps to indicate whether water is safe to drink.

Here, we’ve shared everything you need to know about TDS, including what it is, how it’s measured, the potential risks of high-TDS drinking water, and more.

💡 Understanding TDS

So, what is TDS and what does it refer to?

TDS stands for total dissolved solids. Some of the substances in water that might contribute to TDS include organic and inorganic salts, minerals (dissolved calcium, magnesium, potassium, etc.), water treatment chemicals, and heavy metals.

Essentially, TDS is a measure of all the organic and inorganic materials present in the water source.

The effect of TDS on water quality depends on the impurities contributing to the TDS, but generally, a high TDS level is linked to poorer water taste, aesthetic issues in the home (such as iron staining or hard water deposits), and potential health effects from drinking increased levels of certain contaminants.

📥 Sources Of TDS

Water is considered a universal solvent because it picks up and absorbs impurities from its surroundings, which contribute to total dissolved solids (TDS).

There are two TDS source categories: natural TDS sources and TDS sources influenced by human activity.

Natural Sources of TDS

Some of the natural TDS sources are:

• Mineral springs
• Soil
• Rivers
• Plants

TDS Caused By Human Activity

Some of the TDS in water caused by human influence or activity are:

• Pesticides and farming chemicals from agricultural runoff
• Impurities from urban runoff
• Lead and metals from corroding pipes
• Disinfectants from the water treatment process
• Mineral additives (i.e. in bottled mineral water)

📋 Factors Affecting Water’s TDS Levels

Here, we’ve outlined the factors that affect the level of TDS in a water supply.

Water Flow

The flow speed of a particular body of water can affect its TDS concentrations. Fast-flowing rivers are likely to have more sediment because they cause more disturbance to the rocks and soils they flow over. Water with high currents is also more likely to have an elevated TDS level.

Urban Runoff

During rain storms, solids, sediment, and debris from residential and commercial areas are carried in rainwater into rivers, streams, and other surface water sources.

Soil Erosion

Soil erosion may occur naturally or may be due to human activity, like construction, mining, and logging. The eroded soil particles may travel through runoff into natural sources of surface water, increasing their TDS concentration.

The Presence Of Fish

The presence of certain bottom-feeding fish, such as carp, can also disturb solids, vegetation, and sediments in water sources, increasing the water TDS level.

Influence From Septic Tanks And Industrial Wastewater Discharges

When industrial wastewater plants release discharges into natural water sources, the dissolved solids found in these discharges can increase the TDS level of the water.

Decomposing Plants And Animals

Decaying plants and animals release suspended organic substances. Runoff or direct contamination from these sources contributes to water’s TDS.

📐 How is TDS Measured?

Total dissolved solids (TDS) is measured in milligrams per liter (mg/L) or parts per million (PPM). Both measurements are exactly the same and are used interchangeably.

The secondary drinking water regulations, produced by the Environmental Protection Agency (EPA), report that the maximum TDS levels in water should be 500 PPM.

That’s the highest level of TDS present that’s considered safe to drink. Anything higher is risky, and a TDS level above 1000 PPM is considered unsafe.

If your TDS levels are higher than 2,000 PPM/ milligrams per liter, then you will need to look into installing a specific water treatment system to reduce or remove TDS from your water.

🤔 What Does TDS in Water Mean?

The amount of TDS in drinking water determines its quality and characteristics.

One of the biggest effects of water with high TDS is the likely elevated concentration of calcium and magnesium mineral ions. 

These two minerals are responsible for making water hard, which forms scale deposits in both plumbing and appliances. 

Scale from mineral deposits can cause damage, affect water flow, and leave unsightly stains that are difficult to clean. If you have high TDS levels in your water and don’t have a water softener, we recommend testing your water hardness.

A high TDS level may also give water a slightly salty/ sodium or bitter taste. On the other end, water with a low TDS level has a flat taste and can be corrosive. By adjusting the amount of TDS in your water, you can achieve the desired taste.

👨‍🔧 Read about the difference between hard water and soft water

🩺 What Are the Risks Associated With high TDS?

The risks associated with drinking water with higher-than-normal TDS level ranges depend on the contaminants contributing to the TDS.

Certain total dissolved solids present in water may have dangerous human health effects, or may harm aquatic life, disrupting the ecosystem.

The exact health effects of drinking water with elevated TDS depend on what you’re drinking and for how long, but possible side effects include:

• Nausea
• Vomiting
• Dizziness
• Liver and kidney effects
• Blood pressure effects
• Cancer
• Other chronic health conditions

Generally, elevated TDS levels aren’t an immediate sign of danger. But if your total dissolved solids measurement is above 500, it’s worth investigating further to learn of which suspended impurities are in your water.

If harmful impurities, such as toxic metals and chemicals, make up a large portion of your TDS count, your drinking water may be unsafe to drink.

📊 What Are the Acceptable Drinking Water TDS levels?

Generally speaking, the amount of total dissolved solids (TDS) that you want in your drinking water is up to you. Different people prefer different levels of TDS in their drinking water.

That being said, it’s generally agreed that a TDS level of over 1,000 mg l/ppm is undrinkable.

In 2003, the World Health Organization conducted a study to find out which TDS levels people prefer the most. 0 to 300 mg l/ppm of dissolved solids is the range that most people find to taste the best.

🧪 How To Test For TDS In Drinking Water

How do you measure total dissolved solids in water? There’s no total dissolved solids test – the best way to determine your TDS level is to use a TDS meter.

A TDS meter (which you can buy online) indicates your water’s TDS, and whether it’s considered low, average, or high.

Here’s how to use a TDS meter to measure TDS in drinking water:

1. Fill a glass with water from your faucet.
2. Switch your TDS meter on and place it into the glass of water. A digital reading will appear on the screen. Note down the reading before you remove the meter.
3. Compare your reading to the table above to determine whether you have low TDS, acceptable TDS, elevated TDS, or high TDS.

After installing a water filtration system that reduces dissolved ions, you can then measure your TDS again. Your TDS level should be lower if your filtration treatment has worked.

Keep in mind that a TDS meter won’t indicate exactly which suspended impurities are present in water supplies. So, once you know your TDS level, consider using a DIY or laboratory water test so you know exactly what you’re dealing with.

If you use a municipal water supply, your local water utility is legally required to test the water routinely and produce an annual Water Quality Report for your area. This is another way to learn of the impurities in your water that contribute to TDS.

📈 TDS Calculation Formula

If you currently use a reverse osmosis unit to treat your drinking water, you can calculate the percentage of TDS rejection in your unit and measure the effectiveness of its performance.

Here’s what you’ll need to do:

1. Fill a glass of normal tap water and measure the TDS with the TDS meter, then make a note of the results.
2. Fill a glass with RO water and test the water again, then note down the results.
3. Work out the TDS rejection percentage with the following formula:

TDS % Rejection = [Tap Water TDS – RO Water TDS/ Tap Water TDS] X 100

For example, if your tap water TDS was 260 and your RO water TDS was 20, you’d do the following sum:

260 – 20/260 x 100 = 92.3

🧐 Why is measuring TDS Level Important?

The levels of TDS in your water supply relate to water quality. Even if your drinking water contains total dissolved solids that won’t necessarily harm your health (such as minerals & salts), they may still cause issues in water supplies.

Here are just a few reasons why you should take a TDS reading of your drinking water supply:

1. TDS Can Affect Your Health

Not all total dissolved solids in the water are harmful, but impurities such as pesticides and herbicides, lead, and bacteria pose a serious health risk. Human consumption of some chemicals and impurities, such as chlorine, fluoride, and sulfur, is considered safe if these contaminants are only found in low levels, but they may be dangerous in larger quantities.

2. TDS Can Affect Water Taste and Smell

If your water has a metallic, bitter, chemical, or rotten egg taste or odor, it’s likely you have elevated levels of TDS. Common aesthetic particles that affect water taste and odor are chlorine, lead, arsenic, iron, and sulfur.

3. TDS Can Alert You to Filter Maintenance Requirements

It’s not always easy to tell when your water treatment filter needs replacing. Testing the TDS in your water can help confirm that the filter is doing its job well or determine when you need to replace it with a new one.

4. TDS Can Damage Your Plumbing and Appliances

Hard water minerals like calcium and magnesium are two common total dissolved solids and form scale in your pipes and plumbing. This reduces water flow in your pipes and damage them over time. Elevated calcium and magnesium also damage water-based appliances and shorten their lifespans. Additional corrosive TDS such as iron can also damage your plumbing and appliances.

👨‍🔧 Related: Do I Need a Water Softener? 8 Telltale Signs

5. TDS Can Affect Your Cooking and Cleaning

Certain dissolved solids in cooking water may affect the taste of your food. For instance, chlorine, one of the common chemicals present in city water, may cause your food to take on an unpleasant taste when boiling. Hard water deposits and iron stains can also make your cleaning tasks around the house more difficult.

📤 How to Reduce TDS in My Water?

Here, we’ve shared the best methods of reducing the TDS level in your drinking water.

Reverse Osmosis

Reverse osmosis has a TDS rejection rate of 92-98%, so it’s a great option for lowering the TDS levels of your drinking water.

This filtration unit sends water through several filters and an RO membrane, which consists of tiny pores that only allow pure water particles to pass through, greatly reducing total dissolved solids. Total dissolved solids that are contained through the process are flushed down the drain along with some wastewater.

RO can remove toxic metals and semi-metals such as copper, nitrate, lead, and arsenic, chemicals such as chlorides, salt molecules, magnesium and calcium carbonate, microorganisms such as bacteria, and more.

This type of water filtration system can be installed underneath your kitchen sink or at your home’s point of entry. RO systems are effective in treating high levels of TDS in the water, but excessive magnesium and calcium minerals may damage the RO membrane.

👨‍🔧 Related: How Does a Reverse Osmosis System Work?

Distillation

Distillation is the oldest treatment for purifying water. During this process, heat is applied to water, causing it to boil until it evaporates. The water vapor then condenses back into its liquid form in a separate container.

Water has a boiling point that’s lower than most suspended impurities, the TDS is left behind when the water evaporates. The few TDS that succeed in evaporating and condensing with water are trapped in a carbon filter in the distiller’s spout.

A distiller is a portable filtration option that can be set up on your kitchen countertop within minutes. Water distillers don’t give on-demand access to water – they typically produce 1-gallon batches of water in a process that takes around 3-6 hours.

Distillation, like RO, can remove virtually everything from drinking water, including calcium carbonate and magnesium, inorganic salts, chloride molecules, nitrate, lead, and other undesirable dissolved solids.

👨‍🔧 Related: Purified vs Distilled Water

Deionization

Deionization is based on ion-exchange principles. During this process, water flows through resin beads, and its charged ions are removed.

A cation resin is used to exchange hydrogen in water for other positively charged ions, while an anion resin is used to exchange hydroxide in water for other negatively charged ions. 

This process can be broken down further and you can separate the resin types into two beds or tanks, one for the anions and one for the cations. However, the most effective method is to combine both types of resin into one tank or bed.

The Best Option

We recommend reverse osmosis and deionization as the best methods of reducing the TDS level of drinking water.

The combination of RO and DI resins can remove nearly all impurities and reduce TDS levels to zero, resulting in pure water.

📑 Final Word

Hopefully, you now know everything you could want to know about total dissolved solids in drinking water.

Remember, a high TDS level doesn’t always mean that water poses a health hazard or is unsafe to drink.

However, to stay on the safe side, you may still want to remove as many dissolved particles from your water as possible.

When considering water treatment solutions for TDS reduction, look for systems that have plenty of positive customer feedback and are sold by reputable manufacturers.

❔ TDS In Water FAQs

Is 200 TDS water safe for drinking?

Yes, 200 TDS water is generally safe for drinking. However, if you have any reason to be concerned about your drinking water quality, you should test for specific contaminants before you drink the water.

How much TDS is in tap water?

The TDS concentrations in tap water depend on the water source, but the average tap water supply contains 100-300 mg/L of dissolved solids. Your tap water may have a higher TDS level if you live in an area with a high concentration of minerals.

Is it good to drink high TDS water?

It’s impossible to say for certain whether or not it’s good to drink high-TDS water because the answer would differ in different cases. If your water has higher TDS concentrations caused by high levels of harmful substances, it’d likely be considered unsafe to drink. But if a high TDS was mostly due to minerals, salts, and other healthy dissolved substances, drinking this water would be good for your health.

Is drinking 0 TDS water bad?

No, drinking 0 TDS water isn’t bad and won’t harm your health. 0 TDS water is simply water with little-to-no total dissolved solids concentration. You may find the taste of 0 TDS water unpleasant because it doesn’t contain any healthy minerals that contribute to alkalinity. It’s also important to make sure you get plenty of trace minerals in your diet if you switch to 0 TDS water.

What causes high TDS in well water?

Possible causes of high TDS in well water are minerals and metals that dissolve into the water as it seeps through the earth to reach the aquifer. Common TDS in well water are calcium, magnesium, potassium, iron, manganese, arsenic, and tannins.

Does boiling water reduce TDS?

No, boiling water won’t reduce TDS – or it might reduce TDS by a very small amount, but not enough to be worth doing. Most dissolved solids present in water can’t vaporize when water is heated, so all that will happen is that some of the water will evaporate, so you’ll end up with the same concentration of TDS in a smaller volume of water.

Is TDS a good measure of water quality?

Yes, TDS is a good measure of water quality because generally, the higher the TDS, the poorer the water quality and the less likely it is to be safe to drink. However, certain substances that contribute to TDS are healthy, not harmful, which is why it’s important to test water for specific contaminants if high levels of dissolved solids are present.