Hydroponic TDS For Beginners

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by Miles Graham | Updated: February 26, 2019
In this post we take a super quick look at hydroponic TDS and understand a little bit more about what it is, how it’s measured and why it’s important to your system.

What Is Hydroponic TDS?

Hydroponic TDS stands for Totally Dissolved Solids and is a measure of the number of ions, molecules or particles dissolved in water that can’t be filtered away using a two micrometer filter.We use TDS within freshwater environments (which is why it’s important for hydroponics). For saltwater environments we use the term “salinity”, however, it’s essentially the same thing.

Why It’s Important

Ultimately, TDS is a measure of water quality, however, rather than being a measure of pollution it’s actually a measure of the amount of solids dissolved within the solution but it won’t tell you which solids are dissolved within the water.What you’ll generally find is the higher the TDS level the less that can be done with it.For reference, here are the TDS levels for different water types:
TypeTDS Range
FreshwaterLess than 1000 ppm
Brackish water1000ppm to 5000ppm
Saline water15,000ppm to 30,000ppm
Sea Water30,000ppm to 40,000ppm
BrineOver 40,000ppm
For growers, knowing the hydroponic TDS of your water means you know how much nutrient solution is in the water, however, it won’t tell you what nutrients are in the solution.

How To Measure

The easiest way to measure Totally Dissolved Solids within your water is to either use a TDS meter such as those listed below:
You’ll also find a number of digital pH meters such as those listed here that will be able to test water TDS and EC in addition to hydroponic pH levels.

Hi I'm Miles and I'm one of the growers behind AuthorityGardening.com.
Besides being a passionate gardener and writer, I'm a husband, father and a grandfather to three!