TDS readings

[GDEFR6118]

Question about a reading. I just bought a meter and tested some run off water from one of my auto strains. This will be the second time I’ve introduced nutes to the soil. First time was 1/16 dose. This time was 1/8 dose. Added some cal mag this time and only got a reading of about 450 ppm. My run off reading was nearly 1500. How so high when I’ve put next to nothing in it. My water tests at about 110 ppm. Plant looks healthy

[9fingerleafs]

Are You using soil? You are leeching some nutrients from the soil and thats why it increases

[JeffInCanada]

Hi GDEFR6118 ,
I had the same readings and was asking the same question a few weeks ago. I came to the same conclusion as 9fingerleafs There must be elements in the soil that show up in the runoff test. While I think it is a good idea to do runoff tests with soil/soiless mixes...the PH runoff value is more important to monitor that the PPM. If your plant is looking healthy the high PPM readings are not much to worry about. Below is some more info about testing runoff.