Posted by Jeff Wahl on 12/19/2021 to Water Contaminants
Over the years, it has become apparent that the majority of people are unaware of the presence of total dissolved solids (TDS) in water. TDS are completely dissolved in a water supply and generally invisible to the human eye, detectable only through proper testing. Unmonitored water sources such as dug, drilled or shore wells are more likely to have elevated levels of TDS compared to lake or river water sources. Through observation it has been determined that areas possessing less soil and exposed bedrock have an increased possibility for TDS values that exceed the Canadian Drinking Water Quality Guidelines recommended levels.
Water is commonly known as the universal
solvent, so when it encounters soluble
material, particles of that material are
as a result absorbed into the water.
This process creates total dissolved solids.
TDS in water can come from many sources, including natural water springs, chemicals used during treatment of municipal water supplies, runoff from roads, industrial wastewater, agricultural fields, and even from your home plumbing system.
TDS refers to the amount of minerals, metals, organic material and salts that are dissolved in a certain water volume that is expressed in mg/L or parts per million (ppm). This is usually calcium, magnesium, sodium, potassium, carbonate, bicarbonate, chloride, sulphate and nitrates. Salts used for road de-icing can also contribute to the TDS loading of water supplies.
TDS in Canada
The Canadian recommended guideline for TDS is less than 500 ppm. However, since the Canadian guidelines are not enforceable, each province and territory is free to choose whether or not they will follow the guidelines when determining their regional water policies and guidelines. In addition it is generally not tested for by Public Health Units.
The Role of Hardness in Relation to TDS
Water hardness is a result of dissolved calcium and magnesium in water. It is commonly measured in ppm or gpg (grains per gallon). Locations with higher TDS values are often associated with a limestone rock structure and minimal soil covering, and therefore has a direct relationship with water hardness.
Using the calculation that 1 GPG = 17.1 PPM of TDS, it is very easy to determine how much of the total value is composed of hardness. For example, water containing 20 gpg of hardness contains 342 ppm of the complete value of total dissolved solids present in a water sample. (This calculation can assist as an indication of other solids present in the water as well, such as sulphates, chlorides or nitrates.) Knowing the hardness level in ppm of TDS can identify the need for further testing to determine what the balance of the TDS level is in the water.
Tip for Identifying TDS in Water
One of the best ways to identify the presence of elevated TDS levels without testing is to freeze the water. Once frozen, the dissolved solids will appear as “white flakes” or as discoloured white ice. This is easily spotted in ice cubes as they will “shrink” in size and leave white flakes in the tray.
When Testing for TDS - Compare the Water Hardness in ppm
How to Test for TDS
Testing can be done using a portable hand-held meter available for purchase through various retailers or by taking a water sample to a water treatment dealer who has more advanced meters for identifying TDS levels in water.
Water testing laboratories will also provide this service as a standalone test or as part of a drinking water analysis. Ideal drinking water range is 0-170 ppm with a guideline of >1000 ppm being unacceptable for consumption. All TDS meters require frequent calibration to ensure accurate readings due to the scale build up that can occur within the equipment which can affect testing results.
Best Practice Recommendation
Water quality can vary by seasonal influences and TDS levels can fluctuate with precipitation changes. Properly test a dug, shore or drilled well to determine the water quality on regular intervals. It is also recommended before purchasing a property as part of a real estate sale. Conducting a TDS test is a good practice to ensure the safety of water, verify equipment operation or to install the proper treatment equipment.
Volume 5 - Issue 6 Wahl H2O - Water Awareness
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