Rapid PH drop after res change

Hello all, Everything was going OK and res fairly stable with only slight drop in PH. Decided to do a res change at 3 weeks into flower went in at 1.0ec and 6 PH had to go away for a day so 48 hours later PH has dropped to 4.8 and ec up to 1.1.

I did use chlorinated tap water to flush the system and refill, thought I would give it a day or 2 then add Hydroguard. Res temps around 21. I have adjusted the PH tonight back to 6 and added Hydroguard.

The plants do not have a great root system but there is no rot. Growing in RDWC undercurrent
Any ideas what has caused this?

Has the meter been verified with a calibration? Thats a pretty hard drop for sure.

Renfro said:

Has the meter been verified with a calibration? Thats a pretty hard drop for sure.

Click to expand...

Yea mate just checked it and it is fine. Dropped again today from 6 to 5.3, can't understand why a res change should do this.

fartoblue said:

Yea mate just checked it and it is fine. Dropped again today from 6 to 5.3, can't understand why a res change should do this.

Click to expand...

Might be rot setting in only time my ph drop like this is with on set of root rot. I used current culture uc roots to get back stable after like 3-4 days of use in the res.

That is my fear Jdubb lights don't go on for an hour or so it hasn't been a great day for me so far
https://www.rollitup.org/t/very-very-close-call-how-stupid-you-will-be-shocked.992967/

Try lowering your EC a touch.
In flower my PH went down, and down hard the whole way through.

I get ph drop after rez reset, it always stabilizes after 24hrs or so. I've found running beneficials has helped also

At 3 weeks into flower, your plants are hungry and taking up (out) the P, K, and trace minerals from your fresh res, causing the shift in your pH. Try gently raising your PPM with bloom nutes, or 'spoon feeding' with K and/or CaMg. This assumes there's nothing nasty going on at the root zone.

nxsov180db said:

His EC went up tho..

Click to expand...

I'd wager his water levels dropped in the 48 hour period (plants move/transpire more water in flower) and thus increased the salinity of his reservoir. And/or his EC meter was off calibration for one or both of the data sets.

Cheers,
MM

Certain colonies of bacteria can be the cause of constant downward (more acidic) fluctuations in the solution’s pH.

A good indicator that a bacteria colony is affecting the pH is when the solution’s pH becomes acidic quickly—within a few hours—after initial adjustments have been made. This is especially true if the solution continues to go acidic even after multiple pH adjustments.

When this is observed, a flush of the entire system and a thorough cleaning of the reservoir should be implemented. Cleanliness is the best preventative measure for bacteria-caused pH fluctuations. Using something like hydrogen peroxide to sanitize the system is a good idea.

Depending what nutrients and nutrient forms this can happen but let start at the beginning. Tap water ph will drop as it absorbs CO2 from the atmosphere so it's normal for it to go down for the first 24hrs and agitation will speed this up. Try it for yourself take some fresh tap water test the ph and com back 12 hrs later and test it.

Carbonate and bicarbonates buffer your water and provide stability. Calcium carbonate usually makes up the majority of ppm in your tap water and that usually provides all the buffering you need. That's it's intended purpose in our drinking water so the water does not become acid and react with the piping and coatings.

Decaying organic matter such as roots will also lower ph due to the release of CO2

Nutrients generally will lower the ph of your water... How much depends on the amount of buffering or carbonate/bicarbonate your water contains. The less buffer the more vulnerable it will be to oh swings. There are several good options to help buffer (neutralize acid) your water and provide a more stable ph. The most common is potassium bicarbonate, this is commonly sold as ph up and an extremely inflated price. It's a great option especially in flower and when using tap water since something like calcium carbonate is already contained in tap water and to much of it may throw your nutrient ratios out of whack. In a pinch sodium bicarbonate (baking soda)works well if only small amounts are needed and is usually the case but most like to stay away from sodium.

Take calcium some nutrients contain calcium carbonate or calcium nitrate or calcium sulfate or a combination of each. So depending on the nutrients and sources and the theamiunt of acidity or alkalinity they provide with the makeup of your tap water you may just need to add a buffer like ph up to stabilize it where you want.

TLDR: I would try adding a buffer and check your roots to ensure they are not brown and SLIMEY and may smell like mildew. Some staining from nutrients is to be expected. Let your tap water aerate for 12 hrs before use or 24 hrs standing or allow for some ph drop when phing. The more buffer added the less effect this will have.

One other question are you using a pk booster? Because most use monopotassium phosphate and that can lower your ph. I believe this is why most people see ph starting to fall instead of rise in flower and think root rot immediately.

Aqua Man said:

The most common is potassium bicarbonate, this is commonly sold as ph up and an extremely inflated price. It's a great option especially in flower and when using tap water since something like calcium carbonate is already contained in tap water and to much of it may throw your nutrient ratios out of whack.

Click to expand...

Would something like this be better/cheaper then pH up?
https://www.amazon.com/Potassium-Bicarbonate-Natural-Crystalline-Alkalinity/dp/B00BPUTXGQ?th=1

Keesje said:

Would something like this be better/cheaper then pH up?
https://www.amazon.com/Potassium-Bicarbonate-Natural-Crystalline-Alkalinity/dp/B00BPUTXGQ?th=1

Click to expand...

Absolutely. That's what most ph up solutions are. Potassium bicarbonate diluted in water and marked up about 100x