While salinity or salty water is generally used to describe and measure seawater or certain industrial wastes, the term total dissolved solids (“TDS”) is typically used to describe water high in various salt compounds and dissolved minerals. While one could have very high total dissolved solids and very low salinity from a chemistry standpoint, here we are talking about high TDS with high levels of salts.
Total Dissolved Solids (TDS) refers to the amount of dissolved solids (typically various compounds of salts, minerals, and metals) in a given volume of water. It is expressed in parts per million (also known as milligrams per liter) and is determined by evaporating a small amount of water in the lab and weighing the remaining solids. Another way to approximately determine TDS is by measuring the conductivity of a water sample and converting the resistance (in micromhos) to TDS.
TDS in municipally-treated waters in our area range from 90 ppm to over 1000 ppm. The most common range on city water is 200 – 400 ppm. The maximum contaminant level set by USEPA is 500 ppm.
In some areas, the health departments set the maximum contaminant level at 1000 ppm. Over many years, the United States Environmental Protection Agency has added to and revised a set of standards for drinking water quality. Primary Standards regulate the maximum contaminant levels of certain contaminants that are a threat to health. These include bacteria, viruses, heavy metals, and chemicals. Secondary Standards are suggestions for what the maximum contaminant levels should be for a given contaminant that affects the aesthetic quality of water. These include total dissolved solids, iron, manganese, color, salinity and certain other non-pathogenic contaminants.
The higher the TDS, the less palatable the water is considered to be. Seawater ranges from 30,000 to 40,000 ppm. Many brackish groundwater supplies contain private well water with a TDS of 1500 – 5000 ppm. In some cases, the levels exceed 7000 ppm. Generally, one wants a TDS of less than 500 ppm for household use.
In our experience, it appears that folks can tolerate for general household use, soft clean water with a TDS of up to 1500 ppm. When the levels start to exceed 1500 ppm, most people start to complain of dry skin, stiff laundry, and rapid corrosion of piping and fixtures. White spotting and films on surfaces and fixtures is also common at these levels and can be very difficult or impossible to remove.
TDS affects taste, and waters over 500 – 600 ppm can have an alkaline taste.. When the levels top 1500 ppm, most people will report that the water tastes very similar to weak Alka-Seltzer.
TDS is removed by distillation, reverse osmosis, or electrodialysis. Increasingly, most desalination projects, both large and small, are accomplished with reverse osmosis. Depending on the water chemistry, reverse osmosis systems are the most popular, given their low cost and ease of use. For point of use, at one faucet, distillers work very well also, and produce very high-quality water, but require electricity and higher maintenance than reverse osmosis systems.
For whole-house treatment, commercial-sized reverse osmosis systems are the best approach.
Introduction to Dissolved Solids
Total dissolved solids (TDS) refer to all inorganic and organic substances dissolved in water—like salts, minerals, metals, and organic matter. These can come from natural sources or human activities like farming and industry. Though invisible, high TDS can affect the taste, smell, and look of water. Monitoring TDS helps ensure your water is clean, safe, and pleasant to drink.
Effects of High TDS on Health
High TDS in drinking water may affect health, especially if it contains harmful metals like lead or arsenic. While some minerals are helpful in small amounts, too much can lead to digestive issues or kidney strain. It can also block nutrient absorption or worsen health problems in sensitive individuals. Reducing TDS can lower these risks and improve overall health.
Methods for Reducing TDS
Several methods can lower TDS levels. Reverse osmosis uses a membrane to block solids while letting water through. Distillation boils water, then collects the steam, leaving solids behind. Deionization and ion exchange remove charged particles. The best method depends on your water quality, how much water you use, and what’s in it.
Using a Reverse Osmosis System
Reverse osmosis is a top method for reducing TDS. It forces water through a membrane that traps dissolved solids and metals. The result is cleaner, better-tasting water—ideal for home or business use. These systems are reliable, easy to install, and remove many types of contaminants from high-TDS water.
Alternative Filtration Methods
Other TDS-reducing options include ion exchange systems, which swap out unwanted ions, and activated carbon filters, which improve taste and odor but don’t remove most solids. Distillation and deionization are more thorough but may use more energy. Choose a system based on your water type, needs, and maintenance preferences for best results.
Resources:
- Want More Information about well water? Visit USEPA site about Private Drinking Water Wells.
- Test your well water for TDS.
- Get complete well water testing: See all well water test kits.
Frequently Asked Questions (FAQs)
1. What are total dissolved solids (TDS)?
TDS refers to the combined content of all organic and inorganic substances dissolved in water, including salts, minerals, metals, and other compounds.
2. What is a safe TDS level in drinking water?
The U.S. EPA recommends a secondary maximum contaminant level of 500 ppm. Water over 500–600 ppm may taste alkaline or leave residue, and levels over 1500 ppm often cause complaints.
3. Can high TDS affect my health?
Yes. High TDS may indicate the presence of harmful metals like lead or arsenic. It can also contribute to digestive issues and strain on the kidneys over time.
4. What are the signs of high TDS in water?
Common signs include a salty or alkaline taste, white spotting on fixtures, stiff laundry, and dry skin. Appliances may also corrode more quickly.
5. How can I test TDS levels at home?
You can use a TDS meter, which measures the conductivity of water and provides an estimated TDS level in parts per million (ppm).
6. What is the best way to reduce TDS in water?
Reverse osmosis is one of the most effective and affordable methods. Distillation and deionization are also options, especially for higher purity needs.
7. Do carbon filters reduce TDS?
No, standard activated carbon filters improve taste and odor but do not significantly reduce TDS. For TDS removal, use systems like reverse osmosis or distillers.