One thing we can probably all agree on is that we prefer drinking clean water, not only for health reasons, but also for taste (and smell). Although what constitutes clean water seems simple, it can be murky. There are minerals, contaminants, and sediments that contribute to water’s color, odor, and flavor. But how do you know what’s in your drinking water and whether it’s good for you?

A common way to test is by using a TDS meter. These small devices are used by novices and water experts alike to assess just how many particles are in your drinking water. It’s important to know that the test can be misleading or misinterpreted by those unfamiliar with how it works.

What Are Total Dissolved Solids (TDS)?

Total dissolved solids is a combination of inorganic and organic substances that are dissolved in water, including wastewater. These solids can be salts, minerals, metals, cations or anions. Common inorganic salts that are found as dissolved solids in water include calcium, potassium, magnesium, sodium, sulphates and chlorides. Water may pick up metals such as lead or copper whilst travelling through distribution pipes. Pesticides, fertilisers, leaves and even road salt used in winter months can all contribute to TDS levels.

TDS is usually measured in milligrams per unit volume of water (mg/L). TDS can also be referred to as parts per million (ppm).

Types of Total Dissolved Solids in Water

Now you know the total dissolved solids definition, let’s take a look at the types of TDS you might find in your water. There are hundreds of types of TDS, but they generally fall into four categories: minerals, salts, dissolved metals, and other organic matter.


Minerals such as magnesium, calcium and potassium get into water from natural sources. When water in rivers, streams and lakes come into contact with mineral-rich rocks, small amounts of these minerals are released into the water. Minerals improve water’s taste and contribute towards your daily RDI.


Low levels of salts may occur naturally in groundwater. Salt levels may also be affected by human activity, such as de-icing roads, fertilizer and water softener use, and even sewage contamination.

Dissolved metals

Dissolved metals mainly make their way into water through pollution. Industrial waste and human activities such as mining, can both result in the leaching of metals into drinking water. Rock or soil material may contain small amounts of metals, and some types of metal pipes can also contribute to water’s dissolved metal content.

Organic matter

Dissolved organic matter usually enters into water as a result of the natural decomposition of algae and plant material. In municipal applications, the majority of natural organic matter is removed from water during the treatment process

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How Does Total Dissolved Solids become a problem?

Total Dissolved Solids becomes a problem when it becomes a nuisance. If the total dissolved solids are too low, it is possible that the water may be corrosive to metal piping and fixtures and therefore have a bitter or off-taste because of corrosion byproducts. This may also mean the water could have elevated levels of trace metals either leached from the piping in the home or from the aquifer. If the total dissolved solids are extremely high, the water would have a salty taste, greatly corrode the metal piping in your home, and cause the premature failure of appliances.

An elevated total dissolved solids (TDS) concentration is not a health hazard. The TDS concentration is a secondary drinking water standard and, therefore, is regulated because it is more of an aesthetic rather than a health hazard.

An elevated TDS indicates the following:

  • The concentration of the dissolved ions may cause the water to be corrosive with a salty or a brackish taste as well as result in scale formation, decreasing the efficiency of hot water heaters.
tds meter reading

What are the Health Risks for Total Dissolved Solids?

The measurement of total dissolved solids does not indicate that there is specific health risk or threat, but it can be used to provide insight into the status or the water over time and as a warning sign of a potential problem. Typically, we recommend water users to get a comprehensive initial test that should include a number of parameters including the total dissolved solids of the water and the conductivity of the water. Conductivity and total dissolved solids are indirectly related, but these are two tools to track the change of your water quality with time. In general, a TDS of less than 50 mg/L should raise a concern for a potential corrosion problem, a TDS of over 250 mg/L should raise a concern about the hardness, iron, manganese, alkalinity, chloride, sulfate, nitrate, and general salt content, and over 500 mg/L should raise a concern about other salts (bromide, lithium, aluminum, other metals, and the scale forming potential of the water). A total dissolved solids over 1000 mg/L should raise a concern about the potential for a man-made direct impact or a saline water impact to the source.

How to Measure Total Dissolved Solids

Keeping an eye on water’s TDS may be necessary for a number of reasons. Perhaps one wants to solve a water hardness issue, and measuring TDS will keep track of success. Some may also want to understand why their water tastes bitter, or check that their health is not at risk from the stuff that comes out of the tap. Those with a pool or a spa might want to monitor TDS levels to make sure there are no issues with maintenance.

There are two options for measuring TDS in water: the laboratory option and the at-home option. The laboratory option requires materials and equipment the average person will not own, so the at-home or in the field option — using a total dissolved solids meter — is the better choice.

Total Dissolved Solids Meter

A total dissolved solids meter is a handheld device that can be used to give a TDS reading of a water source. Searches on line reveal TDS meters priced between $10 and $100, depending on the brand and the complexity of the device.

Dissolved solids naturally increase water’s conductivity. A TDS meter, therefore, measures the conductivity of a water sample and uses this figure to determine water’s TDS level. This level is measured in parts per million (ppm) or milligrams per liter (mg/L).

It is important to note that while a TDS meter will measure the concentration of TDS in water, it will not explain what contaminants that water contains. Additionally, a TDS meter can only measure dissolved solids. Some contaminants, like certain metals, chemicals, pharmaceuticals and pesticides will not be picked up by a TDS meter. For more clarity and precision as to what is in a water source, consider water testing.

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