Question on Run-Off PPM

I have a question on run-off PPM measurement. Do you include or subtract the PPMs of your input water? An example; Tap water here has PPMs of about 300, run-off water has PPM of 1200. Are the run-off PPMs 1200 or 900 (1200 minus 300 = 900)? d

Also, is tap water with PPM 320 a problem?


There isn’t a linear relationship between that going in and that coming out. Best practice is to feed with a target of ~1,000 runoff PPM.

320 isn’t much of a problem. Some of it is minerals the plant needs.

In targeting 1,000, subtract the PPM of your water.

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So if your ppm in tap is 300 you would subtract the 300 from your over all after mixed… say over all is 1200 it would really be 900?

I believe midwest is saying, shoot for 700 tds worth the feed, and with the 300 tap, it will come out at 1000 for the feed. At the end of the day, your still just trying to keep the tds around 1000 or a little higher on your runoff. I ride a little higher because with a full strenth feed plus the 180 tds tap im always about 1200 on the feed with jacks. They love it, or i should say loved, since i just cropped


Thanks for the responses; this information is very helpful.

Right on the money.