Consistent High Runoff PH Issue

The last few feeds to runoff I’ve given 5.5PH in and get consistently 6.3-6.5 out when measuring the runoff. I think this is causing a bit of nute lock out too causing deficiencies. I normally feed about 2-3 days, when the coco is dry to the first knuckle but after noticing the high PH of the last feed, the last 3 days I’ve watered 1L of plain 5.5PH water with no runoff to try to lower the root zone PH. Today I fed 2L of 5.5PH’d nutes and measured the runoff at 6.4. What can I do to combat this high PH?

Coco/Perlite @ 60/40
3gal fabric pots
Amnesia Haze Auto & Blueberry Auto - both in week 1 of bloom

Hi @Smokin_Duck how do the plants look??

My first thoughts would be to verify my pH meter if you got a clean fresh bottle of 7 ph solution just verify your getting the correct reading. Good luck

Run 9 gallons of 5.8 PHd water through each 3 gallon pot then give it the normal feeding PHd at 5.8 and you should be good to go.

1 Like

My first thought too. PH pen seems ok. Re-calibrated with proper solution and distilled water too.

Plants overall look good. There is some copper spots in the middle of some leaves of the Amnesia Haze which are also crinkling a bit. Blueberry showing no real signs of an issue.

I’ve heard on other posts that measuring runoff with coco often gives high readings and it seems to be a common issue.

1 Like

Question:is run off that important iv never had run off?Will I have troubles??im in coco and perlite 20 litre pot…I’m no expert!!

With the auto mixed pack Amnesia Haze was the one that was the most finicky for me The. BB and NL was a breeze. sometimes it takes a few tries to get pH adjusted back. I don’t grow with Coco personally but there’s a lot of Growers on here that do. Good luck finishing up


Is your water from the tap? Or are you using distilled water?

@Mat I know @Killadruid doesnt jack with runoff number and he is in coco. You should go follow his journal, he got it goin on.


@Mat it is not carved in stone that you need to get a runoff to check pH and PPM . But it is a great troubleshooting tool can tell you if your pH is too high or too low if you’re feeding too much or you’re not feeding enough.


With flushing, you don’t want to flush with plain water and then feed at the end. Whatever your wanting your medium to get down to is what your gonna flush with. So if you want your pots to be at a 5.5ph with 500ppm, then that’s what you would flush with until your numbers matched going in vs coming out.

You can’t water with plain water, which will strip the medium. At that point, you will still be having your ph issues. Just remember, whatever you want your medium to be at in the end, that’s what you flush with until it matches.


The output PH isn’t going to be a problem even though you are in coco. Watering using low TDS water to adjust PH won’t work as there is nothing there to drive it. If you really want to bring it down; top dress your media with dolomite lime. Follow the package directions.

The tendency of plants as they mature is to see the PH in the root zone drop as organic material dies off. I would submit that you are in a pretty good spot to complete your grow as is.


Using tap water with a TDS around 100 letting sit for a few days to let the chlorine evaporate.
I might swap to distilled and see if it makes a difference.

Here are some pics of the plants.

1 Like

Well u should water to run off to not build up salts in ur medium also to move nutrients around the roots. Otherwise the roots will just be getting the same thing everyday. Also then ur making sure ur getting the whole pot moist. With coco it’s highly recommended to feed to run off.

1 Like

If your letting it sit for a few days are you aerating it with a pump or airstone? Water will go stagnant and wont have the oxygen the roots need.


@Killadruid I agree 100% my choice of words was not good. Monday morning. I was trying to say you don’t have to get the numbers every time. Thanks

1 Like

It all good. Also I would like to point out to treat coco for what it is a hydro medium. When ur plants get big enough they should get feed once to 2 times a day. Unless ur using a promix then it can go down to 1 time every 2 days. I’m on my 4th run with coco I love it.

also dont worry about ur ph comming out just feed at ur normal 5.8. As it water replaces the other water it brings ur medium back into ph level. This is y it important to feed to run off. I’ve also sat there and chased ph left and right figured out with coco just feed at hydro ph levels and good to go. Just monitor ur ppms tho for lock out issues do to to mich nutrients.


Beautiful how many plants do you have. I see you sealed your basement walls.

17 in there I’m currently building a veg room now going to move 10 out into that room and start flowering 7 or 8 of them

1 Like