What is this and what's it for?

A friend gave it to me and aside from water temp I’m not sure what it’s for? I already have a Bluelab pH meter.


TDS Meters/Testers: What You Should Know Before Measuring Your Home’s Water (youtube.com)


Ec meter to test nutrient levels in hydro and soil. Test either the solution or a slurry/runoff. Keep it clean. Necessary for non organic. Living soil you can put it on shelf.


That actual meter is a 4in1 that believe it or not despite being slightly older is actually incredibly accurate when properly calibrated.


maybe I should learn to use it?


It will tell you if your girl is hungry based on the solids (TDS) in your run off. I have been needing to pick one up for mid to late flower issues. I transplant so not really needed since I do not start feeding until 2-3 weeks into flower. Still would be nice to have right? Like a grenade or condom???


I’d you plan on growing “successfully” yes, I would highly recommend learning to use it :v:


lol, well I thought I’ve been growing successfully. But it seems like every week I need a new gizmo or gadget.
Now I’ll spend the night on YouTube learning to use my new toy.


Lol. I am stupid simple. Have all the gear that i never use with living soil. I feel ya. I am a dirt,good lights and water guy.


@Storm I do like simple! My Tds meter sits on the end table, where I set it long ago.

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Hey, I remember those! Back when only a few states were legal.

Your buddy gave you one of the most important tools to cannabis cultivation!

That tool right there will tell you how strong your nutrient mix is and the concentration coming out of the growing media (runoff), those two numbers will tell you how well the plant is feeding.

Seems like a good buddy, he might know a thing or two.


Ok, I guess that’s good. The instrument gives me those values, but how do I learn what they mean?

I’m presently growing 4 autos, and I’m into week 4. Let’s say I feed my present grow a 1/4 dose of FF Grow Big, and also a 1/4 dose of Calmag. I’m growing in FFOF, and the soil was amended with perlite and myco.
The instrument will spew out numbers, how do I know what those numbers mean?


Well first, I would calibrate it and maksure it’s accurate before anything.

You want to see input and runoff numbers similar to each other. With autos they are generally lighter feeders. (Not all but most) iv had really good results with jacks at 700-800ppm in and about the same out. (Light intensity and so many other factors will play an effect on the plants metabolism rate)

Really high runoff numbers will tell you you’re feeding more than the plant can consume and possibly salt build up.

Low runoff will tell you the plant is eating more than you are supplying.
Here are a couple pictures that hopefully help.
These two autos are 41 days old.


This is getting confusing.

Your instrument shows 820. 820 what? I’m not trying to be a jerk, I’m just trying to learn.

I’m presently running a 1000w MH, which I’ll be switching to a 1000w HPS for flower.
I’ll be switching food from FF Grow Big to FF Tiger Bloom, with possibly a small amount of Cha Ching.
So those values will be in a constant state of flux as my grow progresses, won’t they?

ok, I think I’m beginning to understand.

I want to get a numeric value of my nutes right after mixing before feeding.
Keeping that number in mind, after I feed my plants I want to get a new run off number. Then, I compare this number to the first.

If the number remains close to the same, then my plants are not feeding as they should, and not drawing in nutrients. If the number is considerably lower, then that indicates my plants are needing more food.

An I on the right track?


Yep, you’re getting it now. So if you mix up your nutrients at say 1200 ppms and then you read 700 ppms on your runoff, you know that she ate 500 and next time you can feed again. You want to try to maintain ~1000 ppms. When you get less than ~1000 ppms on your runoff…feed. When you get more or stay above ~1000 ppm runoff, water only. You’re getting it…


Using your TDS Tester

This is a simple but very reliable tester that measures the Total Dissolved Solids (TDS) in water. It gives a reading in parts per million (ppm) of all the dissolved solids, good or bad. Dissolved solids in water are mainly its mineral content. If your tap water, for example, has a TDS reading of 250 parts per million, that means that the total content of the minerals dissolved in the water make up 250 parts per million of the total volume.

For practical purposes, TDS measurement is a very effective way to test you reverse osmosis unit’s performance.

To operate:

  1. Remove the cover from the bottom of the tester, then turn on the unit by pressing the On/Off button. The display should read 000.
  2. Insert the tip of the tester (the end where the cover was) into the water to be tested. A half inch or so deep is plenty. You’ll ruin the meter if you submerge it too deeply.
  3. Read the numbers on the display. The number you see is the TDS (Total Dissolved Solids) of the water expressed in PPM (parts per million).
  4. The Hold button and the Temp button are features you probably won’t need. Hold locks the number on the display so it won’t go away and Temp measures the temperature of the water.
  5. When you’re finished, turn the tester off.

Note: The tester is factory calibrated. You won’t need to calibrate it.

Testing your RO membrane:

Measure the TDS of your tap water, then measure the product water for comparison. The RO water should be about 1/10 or less the reading of the tap water. In other words, if the tap water reads 250, the reverse osmosis water should read around 25 or less. What you are measuring is the performance of the reverse osmosis membrane. As long as you get a respectable TDS reading, the membrane does not need to be replaced. Typically, reverse osmosis membranes last three years or longer.

Important: If you are testing a new unit, always wait until it has run for a few days to ensure a reliable reading. It takes quite some time for the newness to wear off the system.

If you are servicing the unit, take your test before changing the carbon filters. New carbon filters will corrupt the reading considerably and read much too high. The meter can “see” the manufacturing residue from carbon filters.
This is a very generalised explanation but this is the gist of it.


@Beard-O it looks like your unit is set to ppt in that first pic you posted which might be parts per trillion, if you can change the scale I’d recommend doing that so you’re comparing apples to apples. Looks like @Storm and @Autos-only have you covered :sunglasses:


I am a chart kinda guy here, and maybe this one will help. There are three different scales for meters to use to convert EC readings to PPM.


You got that right.
More stuff for more weed, is the plan.