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Total Dissolved Solids: A Guide to Understanding and Reducing TDS in Your Water

Our drinking water, whether from a municipal water supply or a private well, is likely to contain contaminants. Some of these, such as chlorine added by the city or lead from pipes, can be harmful to our health. Others, such as calcium and magnesium, can affect the taste of the water and cause damage to our pipes and appliances.

One way to measure the contaminants in your water is through TDS, or Total Dissolved Solids. High TDS levels can make your tap water taste unpleasant, damage your pipes and appliances, and even pose a risk to your family's health.

TDS can be a concern, but there are ways to reduce it. Let's learn more about what TDS in tap water means and how to address it.

Understanding Total Dissolved Solids in Tap Water

Total Dissolved Solids (TDS) are a measure of water quality that measures the concentration of dissolved salts, minerals, metals, and organic material in your water supply. It's expressed in parts per million (PPM) or milligrams per liter (mg/L). One PPM is approximately equivalent to 1 mg/L.

TDS is composed of various chemicals and minerals, but your TDS reading does not provide information about the specific composition. The main components of TDS are:

  • Calcium
  • Magnesium
  • Potassium
  • Sodium
  • Bicarbonates
  • Chlorides
  • Sulfates

A high TDS level may also indicate the presence of harmful substances such as lead, mercury, arsenic, and nitrates from fertilizers, pesticides, herbicides, and insecticides (1, 2).

Note that TDS readings don’t detect all types of contaminants. For example, if there is motor oil or undissolved contaminants such as pesticides, heavy metals, or chromium 6 in your water, they won’t be reflected in the TDS reading.

TDS can be absorbed by water from various sources such as rocks, pipes, agricultural runoff, urban runoff, road salts, pesticides, herbicides, and sediment in well water.

The Environmental Protection Agency (EPA) recommends that TDS levels in your water supply shouldn’t exceed 500 PPM (3). If TDS exceeds 250 PPM, it’s recommended to filter the water. Higher TDS levels can damage pipes and potentially pose a risk to your family's health.

Does a High TDS Mean You Have Hard Water?

Hard water, which has a high mineral content, always has a high Total Dissolved Solids level because it contains a lot of calcium and magnesium carbonates, bicarbonates, and sulfates. However, a high TDS doesn't necessarily mean you have hard water, as other chemicals could also be causing the high TDS reading.

If your TDS is around 350 – 500 and this is due to mineral content (rather than other more toxic chemicals), then it's just hard water. A salt-free water softener is a good solution for this.

Why is it Important to Keep Track of TDS Levels?

There are several reasons why it’s important to keep track of TDS levels in your water. If TDS levels are too low, your water may be flat and tasteless, lacking in healthy minerals. On the other hand, if TDS levels are too high, your water may taste bitter, potentially damaging your pipes and containing health hazards.

Total Dissolved Solids (TDS) aren’t necessarily a negative presence in water. A moderate TDS level, around 50 to 250 parts per million (PPM), can indicate that your water has a healthy mineral content and will taste better. However, a TDS level of over 500 PPM may mean that your water has harmful levels of dissolved impurities, which can be harmful for your health, plumbing, and appliances.

High TDS affects:

  • Taste and appearance: Depending on the minerals present, high TDS water can taste either bitter or salty and always have an unpleasant taste. It will also have a murky appearance.
  • Cleaning: High TDS water can stain clothes and leave mineral deposits on dishes.
  • Cooking: Cooking with high TDS water can negatively affect the taste of food.
  • Health: Elevated TDS levels can also indicate the presence of harmful dissolved contaminants, such as pesticides or heavy metals.
  • Plumbing: Elevated mineral levels can build up in pipes, leading to scale formation. Other contaminants may be corrosive.
  • Appliances: High TDS water can cause limescale to build up in appliances, damaging items like kettles and dishwashers.

What TDS Levels in Water are Good for Your Health?

A TDS range of 50 – 150 PPM is best for your health. Low TDS in water can indicate a lack of healthy minerals, but as long as you’ve got a mineral-rich diet, it won’t greatly impact your health. The main impact of low TDS is on the flavor of your water.

TDS Level (PPM)Affect and Recommendation
Less than 50 PPMSafe to drink, but will be flat and tasteless. Lacks healthy minerals. Remineralization is recommended.
50 – 150 PPMBest for drinking.
150 – 250 PPMOkay to drink, but water hardness may affect plumbing. Consider filtering.
250 – 500 PPMTaste and plumbing will be affected, filtering is recommended.
500 – 900 PPMNot safe to drink, water should be filtered.
Over 900 PPMLikely to contain harmful chemicals. Filtering and further testing is necessary.

What are TDS Meters?

A TDS meter is a small, affordable handheld device that allows you to measure the total dissolved solids in your tap water. They can be purchased online for under $20.

What are TDS Meters Used for?

TDS meters are used to check for sudden changes in your water supply. While they cannot provide a detailed analysis of contaminants in your water, they can confirm any suspicions you may have if you notice limescale build-up or a change in the taste of your tap water.

A TDS meter can also be used to check the effectiveness of a whole-house water filter, if it is designed to reduce TDS. In addition, TDS meters can be used to check the water in your pool or aquarium.

However, TDS meters can’t be used to determine whether your water is safe to drink, as they don’t provide a breakdown of the chemicals, minerals, and particles present in the water. If you want a detailed report on the contents of your water supply, your community water provider is legally required to provide one. However, using a TDS meter will give you an immediate reading of your Total Dissolved Solids.

How Do TDS Meters Work?

TDS meters work by reading the conductivity of a solution, such as tap water. The ions of dissolved solids increase the conductivity of a solution. The TDS meter estimates the total dissolved solids based on the reading of the conductivity.

The Best Ways to Reduce TDS in Drinking Water

If the Total Dissolved Solids (TDS) in your water supply are over 150 PPM, you should consider reducing them with a filtration system or distiller. If the TDS are over 500 PPM, then your water is unsafe to drink.

Reverse Osmosis Systems

Reverse Osmosis, or RO, is a popular method of reducing Total Dissolved Solids (TDS) in your water supply. It uses pressure to force water through a small membrane, removing particles as small as 0.0005 microns.

Whole-house reverse osmosis systems can protect your plumbing, but they are often installed at the point of use, such as in an under-sink system like the APEC Water Systems ROES-50. Reverse Osmosis can reduce TDS to around 25 PPM, so these systems often include a remineralization stage that adds minerals like calcium and magnesium to improve the taste of your tap water.


Distillation is another effective method of removing dissolved solids from water, typically reducing TDS to under 10 PPM. It works by boiling the water in an initial chamber until it evaporates. The steam is moved along a cool surface before condensing in a second chamber.

Since the contaminants that make up the TDS have a higher boiling point, they remain in solid or liquid form in the first chamber, which is then flushed to remove them.

Water distillers usually include a carbon filter stage after distillation, which traps contaminants that evaporated and condensed with your drinking water. The resulting water has a very low TDS and it is recommended to remineralize it.

Distillation is a slow process, typically taking several hours for the water to boil and recondense, but it is an affordable method of reducing TDS if you have the patience.


Deionization uses an ion-exchange process to remove particles from your drinking water, leaving it highly pure. The water is passed along a resin bed precharged with positive and negative ions hydrogen and hydroxyl.

Positively charged ions (called cations) are replaced with hydrogen, while negatively charged ions (called anions) are replaced with hydroxyl. Hydrogen and hydroxyl combine to make H2O, so the contaminants are effectively replaced by the ingredients of water.

However, deionization only targets charged particles, and non-ionized contaminants such as metals and microorganisms remain. Deionization is often preceded by a Reverse Osmosis filter to remove these particles before the deionization stage, which also extends the lifespan of your deionizer.

Other Filtration Systems and Water Softeners

Other water filtration systems, such as activated carbon or ceramic, will not reduce Total Dissolved Solids. These filter membranes only remove floating particles and other chemicals (like chlorine) that they are designed to absorb.

A salt-based water softener is designed to remove hard water minerals like calcium and magnesium from your water supply. These will slightly reduce the TDS of your water, but because they only target specific minerals, your Total Dissolved Solids will remain high.

Total Dissolved Solids FAQ

Here are your TDS questions answered:

How Much TDS Water is Safe for Drinking?

According to the EPA (Environmental Protection Agency), the upper limit for Total Dissolved Solids in drinking water is 500 mg/L (4).

The World Health Organization (WHO) recommends that TDS levels in drinking water should not exceed 600 mg/L. However, the best level for Total Dissolved Solids in drinking water is between 50 – 150 PPM. If TDS reaches around 150 PPM, the taste of the water will start to be affected. Higher levels can also pose serious health concerns. A study in Australia found that high levels of soluble solids in water were correlated with deaths from heart disease and heart attacks (4).

Can TDS Be Reduced By Boiling Water?

No, boiling water won’t reduce Total Dissolved Solids. While boiling water can kill biological contaminants, it doesn’t remove TDS. Distillation, on the other hand, works by boiling water and recondensing the steam in a second chamber, leaving TDS behind. When you boil water, the water and its Total Dissolved Solids remain in the container you used to boil it.

Can You Reduce TDS in Water Without RO?

Distillation and deionization are the most effective methods for reducing Total Dissolved Solids without using Reverse Osmosis (RO). Other water filtration systems that have been designed to reduce TDS include carbon filtration (with filters blocking particles smaller than 2 microns) or using ion-exchange methods.

My Water Filter Doesn’t Reduce TDS. Is it Working?

Not necessarily. Many water filters target harmful contaminants that aren’t included when measuring Total Dissolved Solids. These contaminants, including heavy metals, chlorine, herbicides, and pesticides, will not affect your TDS reading once removed.

If your water filter system is Reverse Osmosis, you should see TDS reduced to below 50 PPM before remineralization. If RO doesn’t reduce TDS, it may be time to replace your filter membranes.


At a certain point, high Total Dissolved Solids (TDS) in your drinking water can be unpleasant and harmful to both your body and your home's plumbing. Therefore, it’s important to measure your TDS and purchase a water filter designed to remove them.

Reverse osmosis systems are very effective at filtering TDS and are reasonably priced.

However, it’s important to remember that TDS isn’t always harmful to your health. In fact, a moderate amount of calcium, sodium, and magnesium can improve the taste of your water and provide health benefits. The optimal level of TDS in your drinking water is 50-150 parts per million (PPM).

Eric Phillips

Hi, I’m Eric, a Plumber, Home Repair Expert and Chief Editor behind Dripfina. I first became interested in water purification and water safety when I spent a couple of years traveling the world. I not only learned the importance of keeping my own water fresh and pure (yes, sometimes the hard way…) but I also saw how important water is as a resource worldwide. Read more about me...

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