First PPM Reading at 21 days- Please comment!

(I apologize for ‘doubling’ this post from ‘Autoflowers’…but I think this is the right category)

White Widow CBD Autoflower
Foxfarm Soil- Happy Frog 3-gallon plastic pots
All waterings up to day 21 have been from my tap water (left overnite to release any chlorine)
Tap water has a PPM of 343
PH has been around 6.3
All three (3) plants look very healthy. One plant looks like it has a flower starting? The others do not, yet.

Today, my PPM meter came. I put 1/8 of a teaspoon of Foxfarm Tiger Bloom and 1/8 of a teaspoon of Big Grow in a one (1) gallon jug of distilled water. As they had not been watered in 4 days, I split the gallon three ways and gave them all thorough watering…
The runoff was extensive as this was the first time I used such a large amount of water, as well as watering the entire top of the pot…as opposed to just a smaller ring previously.
I collected the runoff and combined them all together.
The PPM read 1,702

1.) what does that PPM number mean?
2.) Do I subtract the tap water’s PPM of 343 from that number since I have been watering them their whole life with said tap water?
3.) If so, does that mean the actual PPM is 1,359?
4.) I have some rocks in the very bottom of two of the pots…I thought to enhance drainage. All the pots also have holes and a water catching tray. But will those rocks skew the PPM of the runoff?

Any input would be very helpful as I am at that stage now on my first grow.


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First thing is, you say your girls look healthy, right. If so you should water to approximately 10-20 % runoff with no nutrients included. Check your ppm’s of water with no nutrients added before you water. Whether you use distilled or tap you need to know what’s going in first. It’s important to water slowly until you start to get some runoff. Don’t mix runoff together with other plants runoff check them separately. The idea is to know what your ppm is for each plant before you start nutrients. You asked what is ppm, it’s the measurement of Total Dissolved Solids in your water in parts per million. If you get a reading of 1700 ppm from runoff of a plant it’s telling you that you don’t need to add nutrients yet. If you are using tap water that is 350 ppm then you don’t subtract that from total. Because that is part of the TDS amount. A lot of people will get a RO water unit that removes nearly all of the TDS. Mainly because with tap water there’s no way to know if everything is necessarily bad. For example tap water has calcium and magnesium in it which is good. But it also can contain other elements that isn’t so good. Happy Frog should carry your girls for 4 weeks or so. So get your runoff numbers first and see where you are with the ppm’s.


Thank you—I appreciate the clarity. I will do so-


I agree with what you said here except the fact you can go to tractor supply and get a one use full water test kit for under $50 and it will tell you absolutely everything in your water. What do you think farmers do? Guess? may have been 60 or 70. Can’t remember, but I know it was much cheaper than paying a company 150-250 to come test it.


In Missouri ( not sure elsewhere) I picked up a sample kit from the county health department and for 10 bucks was able to get water test.

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Full? You can get partials at big r for 20. Which is a human consumption test. What I’d imagine a health department giving. Not the same as a horticulture test. Plants are more sensitive than us when it comes to water. When I say full I mean full. Read the instructions and say duck that I’ll hire someone. Lol. But then you look at the price and be like. Okay… I’ll do it.

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No argument here. But for $60 you can get a RO Buddy and be sure that nearly everything is removed from water. That way you’ll know exactly what’s in your water. :slightly_smiling_face::+1:


There are some places in this world where your well water is better than distilled or ro with calmag added back will ever be, don’t want to filter out great for good. Explained on the main site. Like in detail with examples of places that have this water.

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No doubt, but the original question pertains to tap water over 300 +. Which is the same level my tap water is at. I’m just guessing, but I’d say the likely possibility is that’s not a good thing.

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How does your porcelain look if you don’t scrub it for a week? Showers? Most likely yeah, that’s some rough starting water. If your porcelain and plastics aren’t getting rust stains or other deposits though. It’s probably okay to use. But mine is so full of iron, my dirty water gallons will yellow on the bottom in about 10 hours. If it wasn’t for that though, I wouldn’t bother with filtering it.

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I use an RO Buddy. I much prefer to add what my plants need. Once you are more experienced and get it dialed in, it is easy street from there.


I used to have an RO when I had my saltwater aquarium years ago…but I sold it. So, I have my tap water which I leave out for a day or so to reduce the chlorine. But even at 343 PPM that water is what I get from a ‘filter’ in the refrigerator…I haven’t even tested the actual water straight from the tap…it’s gotta be much worse and i never drink it.
I recently used a ‘straight from the tap’ water for one of my humidifiers…in a day or so the entire heating element was a ‘white cap’ of hard minerals. Yuck.
So, my question is:
If I know my best water is PPM of 343, then how does that number play into the next number I will get from my next Run-off water PPM?
Is the current 1702 PPM of the run-off from ‘unused yet’ Happy Frog PLUS built up minerals from my waterings?

Yes you do need to know the ppm of the water before adding your nutrients. 343 ppm filtered by fridge is high. Your filter is shot if you have a LOT of dissolved solids. Well water can be full of lime and other minerals. Ok to use as long as you know what you started with so nutrients can be accurate. City water can have the same as well water, but still 343 is on the high side.
Honestly, I don’t worry about run off. I normally do hydro. Even in pots I am careful of nutrient strength going into the pot. I’ve never had an issue and almost never check runoff unless I have an issue. Often I use my hydro water for potted plants after weekly change out.
Pre-nute water = 343. Add nutes and check again. Pre-Nute - Nutrient = Nutrient PPM.
An Auqa buddie RO system is cheap if you have a place for it. I have a 50 gallon “rain water” barrel which I use to collect RO. Auto shut off. Let me know if you would like some schematics.

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Thanks…I will think about it. Im enjoying my first grow and seeing how I might do it different moving forward-

yeah, I just checked and the filter is played. Im gonna order a new one and then see what that does-

Good luck! :yum: I started thinking it would be fun to try a grow. A few years and few thousand later, things have…progressed. sigh :thinking:
Still a ton of fun! Now it is about quality not quantity. :sunglasses:My favorite thing is pulling open a drawer with at least 5 strains to pick from!

I used to smoke all the time in the 70’s…back then THC was so low we could do bongs and bongs never-ending…then, as the years went by I didnt smoke for decades…recently, I thought it would be interesting to grow some ‘low THC/high CBD’ weed. I always loved growing it as a teenager but didnt really know what I was doing…so, now I’ve got all this science and the plants are doing great! Its ‘White Widow high CBD Autoflower’…well, ‘low THC’ for modern times, right? There is just something really great about a cannabis plant. Plus, I definitly have a ‘green thumb’ and have grown excellent sweet corn, peaches, tomatoes…plus tons of other stuff.
What do you like about hydroponic growing?

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Once you get a hydro system set up and running well it is so easy. Obviously over/under watering is a thing of the past!!
I have a set up that automatically adjust water levels. I check pH and PPM every day or every other day. Since I use the same routines the results are pretty consistent. I can easily leave for several days and not worry about it. Only thing that constricts is caring for my mother plants which are in cloth pots.
Love this hobby!

Thanks for this diagram. I wanted to ask you to look and review my progress over in Beginner- Grow Journal. I posted pics there of my grow under the heading ‘Day 26- White Widow CBD - Please Comment’ , if you would- when you have time.

I wanted to ask you to look and review my progress over in Beginner- Grow Journal. I posted pics there of my grow under the heading ‘Day 26- White Widow CBD - Please Comment’ , if you would- when you have time.