Dissolved Solids​

What are Total Dissolved Solids?

Have you ever wondered what’s in your water? Total dissolved solids (TDS) is a measurement of the amount of all minerals, salts and metals in a given volume of water. It includes everything from calcium to chlorine. The TDS can help determine the quality and composition of your water source.

The Best Measure: Total Dissolved Solids​

Dissolved Solids​

The most common measure of TDS in water is ppm (parts per million). Other units include mg/L and ppb. In order to calculate the total dissolved solids, you must know the volume of your water sample and then divide it by one thousand.

Basically, it’s a measure of anything besides the H2O molecule in your water. You need to know that things like wood pulp and rock aren’t included in TDS readings.

##A Good Rule of Thumb:

TDS should be around 80-200 ppm for a healthy plant. If your TDS is higher than 200, you may need to think about ways to improve the quality of your water source or consider using distilled water in order to avoid nutrient deficiencies over time and root rot.

If your TDS is lower than 50 ppm (considered soft water), your plants may suffer from nutrient deficiencies and root rot.

TDS is a measurement of the amount, or concentration, of all minerals, salts and metals in a given volume of water. Total dissolved solids are measured as ppm (parts per million). Other units that measure TDS include mg/L and ppb. To calculate the total dissolved solids, you must know the volume of your water sample and then divide it by one thousand.

  • Cations – positively charged ions
  • Anions – negatively charged ions

Where Do Dissolved Solids Come From?

A lot of the common dissolved solids you’ll find in your water come from organic sources:

  • Silicatest
  • Leaves
  • Plankton
  • Industrial waste
  • Sewage
  • Runoff
  • Road salts
  • Fertilizers
  • Pesticides

– found in plant tissue, peat and clay

Phosphates – from fertilizers, livestock manure and other natural sources

Fluorides – added to drinking water for dental health reasons. It should be noted that plants don’t utilize fluorides like humans do. Plants only need them if they’re deficient in calcium (plant-specific)

Chlorides – from salt water and ocean spray. By the way, they can also come from human sweat which explains why a lot of plants don’t like to be near people on hot summer days! Chlorides will create chlorosis in your plant leaves over time if it’s not removed before they reach the roots.

Sodium – from salt, soaps and fertilizers

Potassium – found in plant tissue. Potassium is very important for photosynthesis because it helps plants to store energy when they’re not taking care of themselves through the process.

There are also trace elements such as nitrates that can be dissolved into your water over time or added artificially by adding fertilizer.

In order to calculate the total dissolved solids, you must know the volume of your water sample and then divide it by one thousand. Basically, TDS is a measure of anything besides H20 molecules in your water. You need to know that things like wood pulp and rock aren’t included in TDS readings.

How toever, dissolved solids also come from inorganic materials:

  • Rocks
  • Air
  • Lead
  • Copper

Measure TDS in Your Water

Total dissolved solids are measured as ppm (parts per million). Other units that measure TDS include mg/L and ppb. To calculate the total dissolved solids, you must know the volume of your water sample and then divide it by one thousand. Basically, it’s a measure of anything besides H20 molecules in your water. You need to know that things like wood pulp and rock aren’t included in TDS readings.

How TDS Is Measured

Cations – positively charged ions

Anions – negatively charged ions

You can find the TDS of your water by using a conductivity meter, which measures how much current is required to move an electrical charge through a solution or mixture. Conductivity readings are usually given in units called millisiemens per centimeter (mS/cm). To convert from millisiemens per centimeter (mS/cm) to parts per million (ppm), divide by ten thousand.

Ex:  If your conductivity reading is 0.20 mS/cm, you can calculate that the total dissolved solids in this solution are 200 ppm. If your conductivity reading is 0.0027 mS/cm, you can calculate that the total dissolved solids in this solution are 27 ppm.

The higher your TDS (total dissolved solids) measurement, the harder it will be for water to hold onto nutrients and minerals  and make them available to plants and other living things downstream. This means that when your plants aren’t getting the nutrients they need, it’s because those minerals and elements have been dissolved into TDS measurements.

Minerals dissolve in water over time  or are added through fertilizers. When you add fertilizer to soil or use a nutrient rich liquid (hydroponics), this is called “fertigating.”

You should be aware that the total dissolved solids measurement in your water will also depend on how much salt is present.  In general, if you have a higher TDS reading than 0.0027 mS/cm, it’s time to start thinking about what might need to change with the way you’re using and storing your water.

Introducing Electrical Conductivity (EC)

A TDS meter uses the fact that pure water has zero conductivity to measure how salty the water is. Dissolved solids in water also have electrical charges and so by measuring this charge, you can estimate how much salt your water has. It is called a TDS meter but it actually measures EC, or Electrical Conductivity.

It is always best to measure the conductivity of your water in millisiemens per centimeter (mS/cm). To convert from millisiemens per centimeter (mS/cm) to parts per million, divide by ten thousand.  For example, if you have a reading of 0.20 mS/cm, then the TDS of your solution is 200 ppm. If you have a reading of 0.0027 mS/cm, then the TDS on your solution is 27 ppm

What About Parts Per Million (PPM)?

Some people might be bored by this article. Others don’t know what TDS is. It’s not a problem to be bored or to not know what TDS is. But

we’re all going to use water and any time you have a question about what’s in your water, it is worth investigating.

Part per million (PPM) refers to the number of solutes dissolved in one liter or kilogram of solvent. In other words, PPM measures how many milligrams are present for every litre or kilogram of water.

The units that measure TDS include milligrams per liter (mg/L) and parts per billion (ppb).  To convert from mg/L to PPM, divide by one thousand. To convert from ppb to PPM, divide by ten thousand.

Why Does Measuring TDS Matter?

Measuring TDS is important because it tells you how much of the water in your system has been dissolved. The higher your total dissolved solids, the harder it will be for water to hold onto nutrients and minerals  and make them available to plants and other living things downstream. This means that when your plants aren’t getting what they need, it’s because those minerals and elements have been dissolved into the TDS measurements.

Minerals dissolve in water over time  or are added through fertilizers. When you add fertilizer to soil or use a nutrient rich liquid (hydroponics), this is called “fertigating.”

It’s also important to measure your total dissolved solids because the total dissolved solids measurement in your water will depend on how much salt is present.  In general, if you have a higher TDS reading than 0.0027 mS/cm, it’s time to start thinking about what might need to change with the way you’re using and storing your water

How to Reduce the Amount of TDS In Your Water

To reduce the amount of TDS in your water, you can:

– Use less fertilizers (organic or chemical) and/or use a fertilizer mix that has lower salt content. For example, if you are using potassium nitrate with nitrogen at 18%, phosphorus at 12% and potash 19%, switch to potassium sulfate with nitrogen at 27%, phosphorus at 36% and potash 34%.

– Use less water per plant. The more you use, the higher your TDS will be

– Store water in a covered container for no longer than two weeks to reduce the amount of dissolved solids that can leach into it over time from soil or other surfaces, including your hands.

– For hydroponics, use distilled water or RO/DI water *Visit my website for more info about the different types of water you can use in hydroponics!

Carbon Filtration Can

Help Reduce TDS

Some filters can remove dissolved solids in water. Carbon filtration is one example  and it comes with a lot of benefits for your plants and the environment at large:

– It removes many toxic chemicals like chlorine, which often come from tap water or well sources that contain high levels of chloride salt. This means less chance of burning leaves and roots if you use this type of filter to supply your plant’s needs (or using an RO/DI system)

– Carbon filtration also reduces nitrates, phosphates, etc., so less fertilizing will be needed over time; helps reduce runoff into our rivers, streams and oceans where excess fertilizer eventually leaches out into natural waterways leading to algae blooms and other environmental problems

– Carbon filtration also reduces organic compounds in water, meaning less chance of organisms like fungi or bacteria forming on your plants from excess fertilizers. That means healthier leaves and roots with fewer bug populations that can cause diseases such as botrytis blight

– The best thing about this type of filter is the peace of mind knowing you reduced the amount of TDS in your system and did it sustainably! If you’re interested in carbon filters, visit my website for more info!”

Reverse Osmosis

“Reverse osmosis is a process that uses pressure to force water through semi-permeable membranes, making it more pure by removing dissolved solids and other impurities from the water.  This means RO removes salts (or TDS), metals like iron or lead, pesticides, herbicides and even some bacteria.”

The downside of reverse osmosis is that while this type of system will remove many different types of contaminants in your water over time as you use it to hydroponically feed plants, if there’s one thing such systems can’t handle well: salt. The filtered water still contains trace amounts which are too high for most plants to absorb

Distillation

“Distillation is a process of heating water until it boils.

When the steam rises and cools, some molecules condense on the surface of the container while others evaporate completely.”

RO/DI systems are basically miniature versions of distillers in that they remove dissolved solids from your tap or well water by running it through an RO filter first to get rid of salts – which can be high in these types of sources if you live near salt flats or other areas with higher levels – then forces it into another compartment where distilled water collects at one end. This type system does not use filters so any contaminants will pass right through unchanged as they’re removed from the source water; this means no extra chemicals leaching out over time

Deionization

“Deionization is a process that removes dissolved solids by passing the water over resins which are usually made of cation and anion exchange membranes.  The positively-charged ions in your source water will be attracted to the negatively-charged membrane, so any contaminant – like salt or lead for example – with a positive charge will also pass through unchanged while all other substances are removed.”

With this type of system, very little TDS remains in your water because most contaminants have been filtered out; RO/DI filters remove more than you would with DI alone but less than carbon filtration systems do as well

Jenny Brown

By Jenny Brown