Adjusting PPM for tap water?

OldMedUser said:

For all you ppm deficient EC guys so you can become multilingual unit wise. 35 years ago when I went back to school in my 30s to do chem I had to learn the metric system and that was a lot harder than this. Both my ppm pens read in ppm - 50 scale.

Totally agree with the above about not counting water ppm in your total. That's not to say that the minerals in your water aren't having an effect on your grow so I only use RO or distilled.

I have this printed out so it's always handy when talking EC.

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jfarrismu said:

Let's assume someone uses tap water with a PPM of 200. Most guides say to shoot for 500 PPM in veg. So they would add 300 PPM of nutes.

However, someone using water with a PPM close to zero would be adding 500 PPM of nutes.

Does this lower level of nutes (200 PPM) significantly affect growth? Would you suggest correcting? (aka if starting with 200PPM water, adding nutes to get to 700 PPM to equate to the same amount of nutes?)

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amneziaHaze said:

depends what kind of ppm meter you have you have to use different forumals to make EC its not same if you have a 50scale 700 scale or 500 scale....

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problem is you have 200ppm of calcium maybe and thats really strong. almost all nutes will put their own calcium and you will allways have too much....

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