Ph Typically Drops Last Week Or Two Of Flower?

[slimjimham]

So I've got the systems running pretty well. Using uv filtered RO water.

Systems are on a float piped directly from the ro system pumping in fresh 0 ppm water...

It seems the last couple weeks of flower my ph drops and needs regular ph up almost daily the last week or so. This has been happening for a while

The ppm is around 160 on the 500 scale

I'm using a chiller (65*) and uc roots...

Using canna substra nutrients

What do you think is causing this? I swear I'm going to invest in ph dosers at some point.

Other than that the ph goes on a slight rise the rest of flower like it should (ppm goes down, ph goes up)

Any help would be appreciated... Roots look great... Pulling the batch in a few days so I'll post pics of roots after I cut everything down.

Thanks!

 

[ken dog]

Do you have an ORP meter?... As ORP Rises, pH drops.

You might want to turn your UV sterilizer off during this time, as well as discontinuing roots.

It's possible that you are raising your ORP too high.

 

[slimjimham]

What's orp?

 

[ken dog]

ORP is oxidation potential reduction... Or Redox potential.
It measures the potential that the oxidants in your water, have to reduce (destroy), other molecules.

It often signifies the quality of your water.

It is what rises when you add Roots to your water, and helps to sterilize your grow.

 

[ken dog]

In your case, you are sterilizing your grow with UV light, AND UC Roots... Your ORP is probably well above 400 millivolts (Mv)... probably dropping your pH to 5.4 maybe 5.2.

 

[ken dog]

Once I started buying meters and paying attention, the correlations became obvious.

 

[jumpincactus]

As always @ken dog is on top of his game.

ORP is a term used frequently in the water treatment & food processing industry.ORP stands for Oxidation-Reduction Potential. So what is that? The best definition I can give is that “ORP is a measure of the cleanliness of the water & its ability to break down contaminants”.It has a range of –2,000 to + 2,000 and units are in “mV” (millivolts).

What is ORP?
In the world that surrounds us, we do not see it, but there is a continuous exchange of electrons that takes place between substances in the air, in the earth, in water, and in our bodies. This phenomenon is known as ion exchange.

In an effort to reach a state of stability, substances that are lacking electrons are desperately seeking out electrons wherever they can: these substances are referred to as oxidizing agents. On the contrary, substances which have a surplus of electrons are capable of donating their extra electrons: these substances are referred to as reducing agents, or anti-oxidizing agents.

Oxidation-reduction potential, or ORP, is a measurement that indicates the degree to which a substance is capable of oxidizing or reducing another substance. ORP is measured in millivolts (mv) using an ORP meter.

• A positive ORP reading indicates that a substance is an oxidizing agent. The higher the reading, the more oxidizing it is. As such, a substance with an ORP reading of +400 mv is 4 times more oxidizing than a substance with an ORP reading of +100 mv.
• A negative ORP reading indicates that a substance is a reducing agent. The lower the reading, the more anti-oxidizing it is. As such, a substance with an ORP reading of -400 mv is 4 times more anti-oxidizing than a substance with an ORP reading of -100 mv.

Most types of water, including tap water and bottled water, are oxidizing agents as their ORP value is positive.

Alkaline ionized water is an anti-oxidizing agent, as it has a negative ORP value and it is able to donate extra electrons to neutralize the harmful effects of free radicals on the body. Most other types of water are oxidizing agents as their ORP is positive.

The following video explains ORP and shows the ORP level of different kinds of water.

 

[UCMENOW]

Slim.
The pH of the bud boosters are inherently lower and will drive the pH down. This shouldn't be too much of an issue as you'll be slowly diluting as you move towards harvest.

 

[slimjimham]

I've actually just been using

Magical
canna substra a/b
Ucroots
Was using pk 13/14 for week 5

But trying to do everything minus the pk 13/14

... So no bud boosters?

 

[UCMENOW]

Have you contacted Canna inquiring? They seem best qualified to offer insight given you're using their line.

Could also be that you're running at too high of strength in your final weeks. Hit up Canna.

 

[slimjimham]

Canna seems to have horrible customer support. You can only really contact them through email and there is no reply aloud to email so if you have follow up questions you have to reask and prob deal with someone else.

I will hit them up though, hard to believe ppm is too high when its anywhere from 300-150ppm (500 scale) at the last week or so of flower

 

[ken dog]

I mean yeah, what are the chances your ORP is too high... Never heard it before.

Did you turn off your UV?... Did it help?

Enquiring minds want to know.:)

 

[ken dog]

By the way... In case anyone cares... While it is true that as ORP rises with ozone, the pH will drop... With chlorine it is the opposite.
As you add chlorine to raise the ORP, the pH will go up.

Also, the more chlorine you add to make the ORP go up, the more the pH goes up, and if the pH exceeds 8.0, poisonous chlorine gas will be released.

 

[UCMENOW]

In experimenting with O2 gas infusion on my UC I have experienced the ORP approach 500 and saw plants yellow as a result. It seems the rootzone was over oxidizing causing plant stress. I did notice the pH decrease as well, though it actually worked well to counter the natural pH increase from the release of hydroxyl ions by the plants.

 

[ken dog]

Yes, I am currently trying to control my pH with my ORP.
I started at 330 millivolts to get to 6.3... And I raised it to about 350 Mv to put the pH at 6.2... Still experimenting and dialing it in, as 350mV almost takes the pH to 6.1.

 

[UCMENOW]

I personally found some associated plant stress when in excess of 425 Mv. Just a heads up. Good work KD.

 

[ken dog]

Thanks UC...I'm anticipating keeping it below 400 Mv.... Hopefully.