How Do Total Dissolved Solids (TDS) Get Into Your Water?

The term TDS (Total Dissolved Solids) is the cumulative combination of any cations (positively charged) and anions (negatively charged) in your water.

TDS (cations) combined with carbonates, such as calcium (CaCO3) or magnesium (MgCO3) are associated with hardness, scale formation and bitter taste. Cations combined with chloride, such as sodium (NaCl) or potassium (KCl) can result in salty or brackish taste and increase corrosivity.

Having a test for TDS can tell you the total amount but will not identify the nature of these ionic relationships. You can purchase a TDS tester from Culligan’s water testing kit or get a FREE water test from your local Culligan dealer. A TDS tester is typically only the size of your hand, and you can use it again and again as a valuable tool.

Water is classified as an excellent solvent — something that has the ability to dissolve other substances. Because of this, it is able to snag impurities easily. In fact, the purest water, which is tasteless, odorless, and colorless, is the best solvent there is. Water with very few dissolved solids tastes flat; the dissolved minerals in ordinary tap water are part of what gives it its familiar taste.

The EPA classifies TDS as a secondary drinking water standard, which means it is regulated for taste, color and odor rather than as a health concern. The recommended secondary level is 500 mg/L, and because it is a secondary standard it is not federally enforceable. In practice, high TDS usually shows up as scale on fixtures and appliances, spotting on glassware, or a salty or bitter taste.

A typical solution to this problem is a reverse osmosis filter if you are concerned with your drinking water. However, a whole house filtration solution is also available if you feel the need to take care of the entirety of your water system.

TDS can come from a number of sources, and the location of your home, climate, water treatment method, source, and a number of variables can contribute to the composition of your water. Common TDS contaminants can include ionic compounds derived from calcium, magnesium, potassium, sodium, chlorides, sulfates, phosphates and nitrates.

Industrial Wastewater and Sewage – Treatment of both can include nitrates, which is important for animal growth. Algal blooms can be more likely to occur with the availability of nitrogen, causing an uptick in disinfectants being used by your municipality, which can lead to chlorine taste and smell. Phosphates can also be a non-point (water pollution from diffuse) source of TDS from wastewater treatment.

Urban Runoff – One of the leading sources in water quality problems, urban runoff occurs when rainwater runs across impervious surfaces through drainage systems. Some of these surfaces contain gasoline, motor oil, metals and trash, while lawns contain fertilizers and pesticides. Fertilizer is also a source of phosphorous and nitrates. Storm water runoff where de-icing salts are applied can also permeate drainage systems.

Piping/Hardware/Plumbing – The infrastructure of your own home could be the source of dissolved solids – particularly if the TDS is low. How can this be? Water very low in dissolved solids is more corrosive and can draw lead and copper out of household plumbing. Both are regulated under the federal Lead and Copper Rule, which sets an action level of 15 parts per billion for lead and 1.3 mg/L for copper. It is uncommon for household water to be low enough in TDS for this to arise, but a water test will tell you where yours sits.

Sea Water – Sea water, naturally, contains an excessive amount of NaCl (sodium) and other ionic compounds that can contribute to a salty or brackish taste. While there are a handful of desalination plants (designed to remove sodium compounds from sea water) in certain areas around the world, the hard truth is that purifying sea water takes an increased amount of time and energy to break such chemical bonds.

Agricultural/Farming/Irrigation Systems – Just like in lawn treatment, synthetic farm fertilizers have nitrates that can dissolve into the soil. Elevated levels of nitrates also occur in animal waste and compost. Nitrogen is an essential nutrient for plant growth. But excess nitrogen can combine with organic materials on the surface to produce nitrates, which can raise nitrate levels in drinking water sources.

Naturally Occurring Total Dissolved Solids – When water makes its way through the ground, it encounters layers of limestone and chalk. These beds are typically comprised partly of calcium and magnesium bicarbonates. The bi-product of these dissolved solids is hard water. Hard water is common across much of the United States.