TDS Level of Tap Water / Nutrient Solution

by Bob
(Jack and Fish Canada)

The TDS level of the water at my house is 240 ppm. The TDS level of the nutrient solution should be in the 500 to 800 ppm range. Does the range include the 240 ppm, or do I add the 240 onto the 800 for a 1040 ppm reading on the TDS meter?

Answer: Bob- I have read various hydroponic publications for years, and they have been in agreement on this issue for the most part. Many of the articles I have read indicate that if you want to provide your plants with more usable nutrients, than you need to START with cleaner water....such as distilled water or reverse osmosis treated water. The implication here is that you must INCLUDE the 240 ppm from your tap water when you are trying to reach a particular nutrient solution strength.

I can't recall the exact justification they gave for it, but I believe it has to do with the fact that much of the 240 ppm coming from your tap water is made up of calcium carbonate, which, as far as the plant is concerned, sits in for other Calcium compounds that the plant can actually use to its benefit (Calcium carbonate it cannot). Also, the remaining portion of the 240 ppm is usually sodium chloride and potassium chloride, neither of which plants use as food but both of which are ionic compounds that mimic fertilizer salts. So, even though the plants can't use them, they still contribute to the power of the solution to burn the roots. I hope that clears things up a little bit- I guess I remember more about those articles than I thought, lol.