Can someone explain PPM!

So been doin lots of reading and learning from some great folks here on ILGM! I constantly and running across the term PPM. Can some one please explain (in beginers terms) what PPM is/does and why its so important.

As always thanks for all the help!!


PPM is Parts Per Million and is the unit of measure for TDS Total Dissolved Solids. It tells you how much “stuff” is in the water, like minerals, metals, salts, etc. Ideally, a low PPM is desired so you can adjust the water yourself with nutes. With a high PPM, it’s hard to know what’s really in the water.

You can also measure runoff from your pots in PPM to see the difference between what you’re feeding vs. what is coming out the bottom. If the runoff is higher, you know you’re overfeeding and have build-up.

Lastly, you can measure your water before and after adding nutes to measure very precisely the amount you added.

My tap is 164 ppm, my rainwater runoff is about 3-5 ppm.

I hope that helps a little.