Baics of EC

thedude27January 12, 2006


I'm new to hydroponics growing and have a basic question about mixing the nutirent solution. Currently I'm growing some sage in a homemade DWC system and was wondering if I'm mixing the nutrient solution correctly.

When you are mixing to obtain say 1500ppm nutrient solution do you add the 1500ppm on top of the reading of your water without solution? So if I had water that was reading say 500ppm before adding anything would I then add solution to bring the reading to 2000ppm? or could that provide your plant too much of a certain nutrient (obviously something is in there raising the count).

Also at what point(well water) hardness would you consider using distilled/spring water? For me its not such a big deal since my grow is small for now, but it would be easier to just use tap water(or filtered tap water).

Thanks in advance for your help.


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The PPM in your tap water is the same whether you have a tablespoon or a gallon. The PPM of the solution from the nutrient concentrate will depend on the volume of water you mix with it. Need to keep in mind that PPM is always a calculated value not like EC (electrical conductivity) which is directly measured. This is why many prefer using an EC meter for measuring nutrient concentration versus a TDS (total dissolved solids) meter, which is an EC meter with a calculation algorithm built in. Unless otherwise stated on the label, the calculated PPM of the solution will assume mixing pure water with the concentrate. But to answer your question the final PPM will be additive and 2000 PPM would be correct.

    Bookmark   January 13, 2006 at 5:40PM
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Thanks a bunch Hank, that helped a lot :)

I guess I should have gotten the EC meter instead of the PPM but I got a really good deal on a Newport DSPH-3 (desolved solids/PH) that I couldn't pass up. Although I'd imagine I could just get the conversion formula from the company and reverse the calculation (although I suppose I'd need accurate temprature readings too).

Thanks again

    Bookmark   January 14, 2006 at 11:29PM
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Dear Thedude27,
I have been growing vegetables hydroponically since the early 1970s. I gave conductivity meters away because I could never correlate its reading with what I knew was in the nutrient. I place great faith in a properly calibrated pH meter.
I invite you to have a look at my web site from Australia.
I use coarse sand as a medium and mix all of my own nutrient solutions ... and you can do the same. I even show you how to make your own system (without using bleach bottles).

Here is a link that might be useful: Simple Sand Hydroponics

    Bookmark   February 5, 2006 at 7:01AM
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