A total dissolved solid (TDS) is a measure of the combined total of organic and inorganic substances contained in a liquid. This includes anything present in water other than the pure H20 molecules. These solids are primarily minerals, salts and organic matter that can be a general indicator of water quality. High TDS generally indicate hard water, which can cause scale build up in pipes and appliances. Scale buildup reduces performance and adds system maintenance costs.
As we learned previously, many dissolved inorganic water contaminants or impurities exist as ions in solution, the most common of these ions are:
These electrically charged dissolved particles make ordinary natural water a good conductor of electricity. Conversely, pure water has a high electrical resistance, and resistance is frequently used as a measure of its purity.

Cations Anions Calcium Ca+ + Bicarbonate HC09­ Magnesium Mg++ Chloride Cl Sodium Na+ Sulfate SO,-­ Iron Fe+ + Nitrate NO,­ Manganese Mn+ + Carbonate CO,_ _

Since only a few of these most common ionic water contaminants are health related, most natural water supplies are safe to drink from the standpoint of dissolved inorganic chemical contaminants. However, even though found more rarely - and in much smaller quantities - certain inorganic ions can be toxic. Turbidity and bacteria are examples of suspended water contaminants.

Total dissolved solids in water

In addition, water supplies can contain dissolved organic chemical contaminants which are usually pollutants that enter water as a result of man's activities, such as insecticides, pesticides and herbicides. These are usually chronically, rather than acutely, toxic to man and other species in extremely small amounts. Trihalomethanes are dissolved organic contaminants, such as chloroform, which are formed in extremely small amounts by the reaction of chlorine used to disinfect water, with humic and fulvic acids from soil erosion. Other organics can enter both surface and groundwater through waste dumping, such as trichlorethylene, tetrachlorethylene (TCEs), polychlorinated biphenyls (PCBs), dioxin, etc. Many of the organic contaminants are probably carcinogenic (cancer-producing). The organics do not necessarily exist in water in the form of dissolved ions.
The Secondary Drinking Water Regulations control contaminants in drinking water that primarily affect the aesthetic qualities of water. Several of these -- chloride, sulfate, copper, iron, manganese, zinc, and total dissolved solids -- are ionized contaminants.
Color and odor are contaminants which cause objectionable sensory responses to the water.
pH is a measure of the acid or alkaline strength of a water supply and corrosivity refers to the ability of a water supply to disintegrate pipes and containers.
Why should you measure TDS levels in your water?
When TDS levels exceed 1,000 ppm (parts per million) it is deemed unfit for human consumption. A high level of TDS is an indicator of potential concerns and should be investigated before drinking. Even the best water purification systems on the market require monitoring for TDS to ensure the filters and/or membranes are effectively removing unwanted particles from your water.
We are all affected by toxic chemicals in the air and food that we consume. Water is the only way to flush out these toxins so it is important to make sure your water source is providing pure water. This is especially important for children because they are much more sensitive to contaminants because their defense systems have not fully developed. The purer the water is the greater its ability to purify and cleanse the body, so drink up!