pH doesn’t budge, even after flush. Getting serious, What do I do?!?

Hey all, my plants pH has been stuck at a solid 5.8 for as long as I can remember. After two flushes, one where PPM went as low at 650, and then one where I took the PPM all the way to 450 until the leaves started to look nutrient deficient. pH never budged, and today after watering with nutes pH dropped to 5.5 :frowning: I’m at a loss of what to do, the plant looks great besides what looks to be either phosphorus deficiency or bad airflow. Planted seed March 28th, switched lights to 12/12 4 weeks ago today. In FFOF, temp is mid 70s low 80s, humidity is 35%-50%. Strain is supposedly Boston Runtz. Anybody have any idea on how I can fix the ph? I’ve double checked the water and made sure it’s anywhere from 6.2-6.5 before watering, and I do know to add nutes before pH adjuster. pH pen is cheap but properly calibrated. I’m completely stumped on how to solve this issue


Your plant looks great.
For me, I would not be worried


In terms of flushing, I assume you were using ph’d tap water? If you use RO or anything similar it won’t change the pH, it’ll just lower the PPMs. what was the run off pH that you achieved prior to feeding with nutrients?

It can take up to 15-25 gallons to flush a 5 gallon pot.

You run the phd water through the medium until the run off is in range before feeding.

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I was using tap water, ppm averaged about 200. I flushed for about two weeks each time and pH never budged, and if I had continued to flush any longer the plant would start to stress over nute deficiency. pH was a consistent 5.8 until today, after I decided to end the flush and start using nutes again. Plant was starting to look really gross, but is starting to look good now. The pics I’ve posted are about 6 hours after watering.

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Flushing isn’t something that should take 2 weeks, it’s done in one sitting. You should be pH’ing the tap water to 6.8 and running it through the medium. There should be no consideration for PPMs here, at all, just getting the pH corrected.

Literally in one session until the run off is in the pH range. After it’s where it should be you Immediately are following with a full strength feed in the same session. This feed because it’s flower should be around 6.8ph. This feed should start to restore the nutrients in the medium that you just washed out.

That means you run a couple gallons through it, check run off, run a couple gallons through it, check run off, and so on until the pH is proper.

With multiple plants there’s been times when it’s taken me 100+ gallons.

The flushing you are doing is typically what some people do at the end of flower. It’s not the same.


Aaaaaah, that makes more sense. I always just thought doing that would drown the plant. I can do that tomorrow, what’s the best way you would recommend to treat 20+ gallons of water with pH?

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This is where a water reservoir comes in handy, but I’ve done it multiple times with 5 gallon buckets. Dechlorinator would be good to use if you are worried about chlorine, or the stuff to treat fish tanks if you have choramines.

I use tap primarily and I haven’t had any issues whether or not I used a product. But everyone’s water is different.

It won’t drown the plant if your soils dry between waterings. Overwatering happens when you are feeding too often.

Now before you 100% commit to the idea I’d recommend a slurry test to get a closer representation of your soil pH

After that consider the health of your plant, see any problems with it where the pH already is? drastic pH changes can cause stress, but this really depends on the plant. Sometimes it effects them sometimes it doesn’t.

If there are no problems now you could consider supplementing lime it raises the pH over the course of a couple weeks maybe more I can’t remember.


I do have soil lime I can add, I’ve just held off in hopes my “flushes” would fix them. Thanks for the great advice

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No problem. I actually had the exact same problem in happy frog, mine were in much worse shape though. I was flushing endlessly and still ended up using lime.

Use your judgement. I don’t want to push you one way or another. Multiple ways to skin a cat so do what you want. :call_me_hand:t3:


I’ve tried all I know, so I appreciate the advice lol. This will definitely be what I try next, first a proper flush and then lime if that doesn’t work

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@Adrjon99, I’m curious what set you on the mission to change the pH. Were your plants showing any problems? You said they started showing deficiencies after you flushed to 400ppm, and that would be expected, but what was wrong before you started flushing?


@Cap_Ron For as long as my stoned brain can remember, the pH has been 5.8 and I’ve been finding leaves that have started to dry. I’m not worried about the red stems really, since the plant has always had them, but I’m starting to think the dying leaves might be related to pH. Not off enough to drastically affect the plant, but off enough to gradually affect the occasional leaf. It may also be air flow, as my only fan inside is a tower fan from Walmart on Medium. I have a 10” fan on the outside to pull out air, and don’t really worry about an inlet fan since my tent is homemade and isn’t completely insulated and littered with holes. I am a newbie on my first grow, so I may very well be wrong on both counts, but the only way to find out is to do something about it, so I’ll keep y’all updated!


@Adrjon99, in my opinion a lot of growers resort to flushing way too quickly.
It’s important to understand that runoff pH can be somewhat of a guide, but it’s not an accurate representation of what your soil pH is. I also think that many users here suggest flushing with higher or lower pH solutions in an attempt to correct a problem that might very well not exist, and before asking all the necessary questions. Depending on your issue, I don’t consider that a very good idea.

I check my runoff EC/TDS on a regular basis, but I only check the runoff pH if there’s a problem. A few years ago I wasted 200 bucks on a soil pH pen. I say wasted because I used it a couple of times and realized that my soil pH was in a perfect range even though my runoff indicated otherwise, and haven’t used it since.

There’s a lot going on in the root zone of a plant growing in soil. Depending on your brand, nutrients, additives, microbes, fungi, ect, many things are contributing to your soil pH, but not reflected in the runoff.

Quite honestly, runoff pH of 5.8 in a soil grow most likely was not negatively impacting your grow, but flushing your nutrients out and making your plants try to adjust to drastically changing EC/TDS levels is like kicking them in the jewels, lol.


I don’t worry until I see my plants telling me they don’t like something. Those plants look fine and happy to me. I would just keep oh at 6.2-6.5 like you have been.


Be careful with dechlorinators. Also if youre growing in soil are you checking runoff and ph because of salt based nutes?


I recently have been experiencing with using the evap water coming off my main ac unit. Just for laughs i checking my drain bucket beforw dumping it. The water collected ph was 6.08 and the ppm reading was 47. So far after a month of using this water i see no ill effects, and i barely have to use any ph adjustments when adding in nutes. As anyone else every tried using collected evap water on your plants?

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@TeNNWisKeY, it’s perfectly fine to use water collected from a dehumidifier or air conditioning condensate line. I’ve been using it for many years. The EC/TDS reading should be close to zero, and the pH reading you’re getting isn’t a true number. In water that has no mineral content your pH pen is giving a false reading because there’s nothing for it to detect.

It’s important to keep the collection bucket clean, that might be why your EC/TDS readings aren’t closer to zero.

Once you add nutrients to it, then it’s important to check and possibly adjust the pH before feeding the plants.


Ill definitely wash out my collection bucket. But yes the only time i use ph adjustmenters is on feding days. The nutes plus water end up about 5.4, so i have to bring the ph up for feedings some. My watering tank i have to add some ph down too about every 3 days. For some reason in my tank the ph slowly raises up to 7ish.



That’s why I asked if there were any significant problems. Any time I’ve used FF soil from the local place pH has been high 4’s to low 5’s and nearly killed a couple plants. Took 2 months to correct. They were on a path to die until I got it straightened out.

Slurry tests from root zone, top, and run off all read the same. However the soil came incredibly hot at over 4500-5500 PPMs for happy frog. It was a terrible experience.

This is what inevitably pushed me to coco. Virtually problem free since.


Excellent stuff here, both the details of what and how, and the analysis of why and when. I appreciate it all gang thanks! Good to see your plants healthier @Adrjon99 yoire gonna have buds to smoke :partying_face: