Need help understanding what PH & TDS are telling me please


Hello every one. I am going crazy and could really use some help understanding what the PH meter and TDS meter are telling me. I am sure the info given here will help many out in the future as well. I spent hours searching every phrase I could think of and could not find just what I need.

First, The PH meter. It is a no brainer to set the ph to what is needed. The same goes with checking the run off. Here is what I don’t under stand what it is trying to tell me.
Say I ph the water to 6.0 before giving it to the plant. I later check the run off and it is now higher at 7.0 or lower at 5.0 Does this mean I should adjust it to a 8.0 to get the run of to a 7.0? Or opposite to get the number lower. or does that part really matter?

Second, the TDS meter. Same goes for it. Reading it is no big deal. Knowing what it is trying to tell me is. So say I mix and get a reading of 750ppm. I water, then check the run off in a few. Not is says 1050. Does that mean the plant is not using any thing? How would I adjust for that? If I need to at all.

I think if I can understand these 2 things. I can begin to fix and prevent some of my issues.
Thank you for all the help you keep providing me.

As an example. I flushed my plants 3 days ago to get a fresh start.
I only used water for the last 3 day which includes today.
Looking at the chart. You can see my run off numbers keep going up for TDS and down for the PH. This is driving me crazy.


@latewood @Countryboyjvd1971 @garrigan65


If your ppm are going up after feeding say you starting with 1000 ppm and tou feed your plant and run off is at 1500 ppm then your plant isn’t taking up all the nutrients in the soil but as long as its still in a exceptable range no worries just slow down a little on feed maybe water gor the next two cycles
Your ph on the other hand should be more consistent if you ph to 6.5 cause your in soil and ph of run off is 6 then yes water at 6.8-7 ph range and collect about 20% of that in the form of run off then check agian it should be higher and in the exceptable range
I always ph at 6.5-6.6 range and my soil stays in that range
If it goes up youll need to lower the ph if it say @ 7-5 i wouls water with 6.1 - 6.2 and redo run off test
See where you are
Hope this helps and doesn’t confuse you :wink:


Thanks and Sorry, I should have added I am using coco coir.I also mean no disrespect to any one that tried to help me with this before. Until I understand this 100%. It will drive me crazy. I have 2 plants that the run off is very close to what I put in. it is the other 2 that keep dropping. I haven’t fed in 4 days. I also flushed one of those days. I don’t understand why my numbers keep dropping. I used a ph of 6.5 today and my run off was 4.5. So should I try a 8.0 tomorrow to try and get it back up? I am only adjusting the ph for the 2 problem plants.
I have super hard water here if that makes any difference. it is 530ppm. I mixed half distilled water and half tap today. No difference in the run off numbers. Friday I will start using bottled water. or the stuff from the machines out side the stores. I am going to get a gallon today and check the tds in it to see if it will put me under the 200ppm. Why are my numbers dropping so much since I am only using water right now? I am afraid to feed right now for fear of getting the brown leaves back.


have you calibrated your ph meter lately? those are some wild swings. @Countryboyjvd1971 could salt build up cause this?


Didn’t see you there… page hadn’t updated I guess so I tagged you too


Fill this out the best you can, and pictures if you can would be huge help
COPY/PASTE the below list into your forum post.
Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so = NA
Strain; Type, Bag seed, or NA
Soil in pots, Hydroponic, or Coco?
System type?
PH of runoff or solution in reservoir?
What is strength of nutrient mix? EC, or TDS
Indoor or Outdoor
Light system, size?
Temps; Day, Night
Humidity; Day, Night
Ventilation system; Yes, No, Size
AC, Humidifier, De-humidifier,
Co2; Yes, No
If you can, upload a picture of your plant. It helps the diagnosis, if needed.
Add anything else you feel would help us give you a most informed answer. Feel free to elaborate, but short, to the point questions and facts will help us help you


Yes, very hard water makes it difficult to keep Ph where you want it because of the buffering. Don’t give up, you’re on the right track. If your Ph keeps dropping just keep trying to raise it until you get it where you want it. Using bottled water might help, but every time you add nutrients to the water it’s going to go down, so just realise it again.


[quote=“Sasquatch, post:7, topic:18345”]

@Sasquatch My meter is only about a month old. I did calibrate it then. I always rinse both meters in distilled water before putting them away. Plant 1 & 3 have the really low ph. #2 and the AK both have run off of 5.7. So I would think the meter is ok. I am headed down right now to get some of the filtered water to see what it reads. I am hoping to be able to use it to get the ppms down TDS wise.

Strain; Type, Bag seed, or
Generic are the problem plants. The AK-47 is fine

Soil in pots, Hydroponic, or Coco?
Coco coir w/20% miracle grow perlite

System type?

PH of runoff or solution in reservoir?
PH 4.6

What is strength of nutrient mix? EC, or TDS
1/4 strength flora bloom trio

Indoor or Outdoor

Light system, size?
two 450w Viparspectra led’s

Temps; Day, Night
average high 78 Low 66

Humidity; Day, Night

Ventilation system; Yes, No, Size
yes, 6" fan/carbon filter & Two 6" fans

AC, Humidifier, De-humidifier,
Small dehumidifier in the 4x4 tent

Co2; Yes, No

This was 3 days ago before flushing all 3

This was yesterday after trimming the bad off. It still looks like this morning. I am now searching for how to keep them this way.


I have what he needs but i Still cant connect. I’ll try and find a way to get it to him and it’s FOR coco


That’s cool. @Not2SureYet looks like @garrigan65 got your fix. hes been having computer issues today… so hes a bit slow but hes the man to fix it


Thank you. I just got back from the store. Starting tomorrow. I will be using water that is only 23ppm. That has to help a little.
Not to go to far off topic though… What I am understanding for the ph. I need to keep raising it till I get a run off close to what I am putting in correct?

If I am putting in say,1000 ppm total when feeding. The run off should be lower than that correct? And if it is higher. What would I do to correct it.


Wait for @garrigan65 to get you the fix, He can possibly explain this to you better. Hes got a ton of info


I never realized how lucky I am about how good my water is until I read some of yalls post and how bad your ph and ppm numbers are…no filters out the tap mine is…ph 6.4. And ppm 53…@Not2SureYet hope you get it brother…these guys will not steer you wrong


My tap water ph 6.2 and 2ppm
not 2 ppm but 2 tds


Good ole well water can’t be beat, I’m betting you have a well…


yepper! I got a creek by the house, I phd the water in it 6.7


Lol…same here…my driveway crosses a creek…but have never ph the water…hmmmm…new idea brewing


I thought about rigging up a way to pump the creek water to water the flower and veg garden. its a long haul have to be a big pump


That’s low ppm @Sasquatch I’m on a well and my water ph is 6.8 and ppm is like 28-32… I thought I was low… lol