TDS Measurement: All Important Questions Answered

Today, various types of water purification systems are used across the world to ensure access to clean water. Although these purification systems are designed to remove the worst type of bacteria and unwanted elements in water, there are various aspects of water chemistry that one needs to consider before buying filtration equipment for their residential, commercial, or swimming pool applications. Knowing the amount of total dissolved solids (TDS) in water is one of the important requirements that helps determine the efficiency of a particular water treatment device in removing bacteria or unwanted elements in the water.
What is TDS?  How is it measured? Why is TDS measurement important? Read the post to know these answers.

A Brief Discussion on TDS

Unfiltered water or water in its purest form, which is freshly extracted from a natural source, may feature dissolved minerals and other substances in it. These dissolved minerals are known as Total Dissolved Solids or TDS for short.  They may comprise inorganic and inorganic minerals, metals, anions and cations. The following are a few common constituents of TDS:

  • Calcium
  • Magnesium
  • Potassium
  • Sodium
  • Chlorides
  • Bicarbonates
  • Sodium and potassium cations and carbonates
  • Sulfates
  • Nitrate

Of these, the first four constituents are anions and the rest are cations. The TDS elements mentioned here pose no risk to human health, and are identified as parts per million (ppm) or milligrams/liter (mg/L).

TDS Water Chart: A Good Reference for TDS Measurement

During a study by the World Health Organization (WHO), the testers offered their conclusions on the acceptable TDS levels in the water. They are as described below:

Level of TDS (Milligrams Per Litre) Rating
<300 Excellent
300-600 Good
600-900 Fair
900-1,200 Poor
Above 1,200 Unacceptable

The United States Environmental Protection Agency (EPA), which sets regulations for drinking water has not set the upper limits for TDS because it is considered as a secondary standard, which means it is not harmful. Many people consider TDS to cause cosmetic, technical, or aesthetic effects. In spite of these considerations, it is always recommended to keep the level up to 500 ppm for the drinking water.

The low concentration of TDS is known to produce bland or flat tasted water, which many people dislike. However, high concentrations may produce hard water, which may leave deposits on fixtures such as pipes, boilers, pool liners, and so on. This higher concentration of TDS may also impair the taste of water by making it acidic, bitter, salty, and brackish. Hard water is also known to damage the water filter demanding regular repair and maintenance. Higher levels of TDS can be an indicator of the presence of harmful contaminants in the water such as sulfates, iron, manganese, arsenic, and bromide.

TDS Meters

Is TDS the Same as Total Suspended Solids (TSS)?

TDS and TSS are two different elements. TSS imply solids that possess pores bigger than 2-micrometers, whereas TDS has pores smaller than 2-micrometers. Any easier distinction is that suspended solids tend to make the water cloudy and visible to the eye.  Whereas the dissolved minerals usually can not be seen and the water appear to be more clear.

What Are the Sources of High TDS?

TDS may originate from a number of natural sources and human activities. The following are a few sources of high TDS:

  • Mineral Springs: The water that originates from mineral springs have high levels of TDS because it flows through a region with high salt concentration.
  • Prairie Areas: The water sources that exist in these areas are found to have high levels of TDS owing to the high concentration of magnesium and sodium in the ground.
  • Flow Rates: The flow rate of water is known to have a direct effect on the TSS and TDS. The TDS concentration is known to increase with the increase in the direction and speed of the water current.
  • Human Activities: It is often found that water sources near the agricultural lands have high levels of TDS. Similarly, urban tradeoff activities such as industrial wastewater streams, wastewater discharges, and so on, also have high levels of TDS.
  • Soil Erosion: This is usually brought by the troubles on the land’s surface. These troubles may be human inflicted or natural. The eroded soil has particles that will be carried via storm water to the surface water, thereby affecting the TDS concentration.
  • Rotting Flora and Fauna: As the flora and fauna near the water sources or that are suspended in the water decay, they produce organic particles, which may lead to an increase in TDS and TSS concentrations.
  • Coastal areas or locations new to mining operations:  There areas may contain high levels of sodium and chlorides which are the most common of all elements found in water.

Why Measuring TDS is Important?

As said before, high concentrations of TDS may alter the taste of the water; additionally, it would help analyze the overall quality of water.

  • Health: High TDS concentrations are not harmful for human health, but the concentration of metal substances such as copper, lead, or arsenic may bring health hazards. If TDS levels exceed more than 1000mg/L, then the water is considered unfit for human consumption.
  • Performance of Filter: Water testing for TDS determination is important to understand if the equipment under consideration has a high rejection rate. Also, if the equipment will require regular maintenance or repair.
  • Industrial and Commercial: High TDS concentration may affect the functioning of several applications such as cooling towers, boilers, pumping units, and so on.
  • Pools and Spas: Like drinking water, it is always recommended to keep the TDS levels up to 500 mg/L for pools and spas because high levels may impact pool linings and other equipment, demanding regular maintenance and repair.
  • Aquaculture or Aquariums: Aquatic environments are sensitive to mineral concentrations. Any increase or decrease may have adverse effects on aquatic beings living in aquariums. So, the water must have the same levels of TDS as in a regular pond or other water sources where these beings reside.
  • Agriculture and Livestock: Water with high salt content can stunt or kill many type of crops and high salinity can cause a laxative effect and dehydration for most livestock. The smaller the species, the more susceptible they are to salinity.

How is TDS Level Measured in Water?

The TDS levels are measured using TDS meters and water testing kits. The TDS meters are mainly offered as portable or benchtop mounted, so you can choose them accordingly. However, TDS measurement chemical kits may be offered as individual kits or as a part of kit featuring chemicals for measuring chlorine levels or other elements.

How to Reduce the TDS Level in Your Water?

There are several ways of reducing high TDS levels in the water. The following are a few common methods of reduction:

  • Reverse Osmosis (RO)
  • Carbon Filtration (minimal effect)
  • Nanofiltration
  • Distillation
  • Deionization (DI)

The choice of the right method will depend on the results of water testing. It is important to use a reliable water testing kit or device to determine the constituents of water. Intec-America offers various types of reliable water testing kits. The company was the first to introduce copper-ionization systems for water filtration. Based on NASA-developed water treatment technology, these systems are adapted for swimming pools. The company offers various water treatment technologies including water filtration, RO, ozonation, tannin removal, UV light, and so on.