PH Calibration

I have been noticing the PH in my reservoir hanging out in the high 6.5. So I calibrated the PH probes, and have been doing a health check on it once a week.

So far, the grobo prompted me to re calibrate the probes 3 times already. I have had my Grobo for almost a month now. Is that normal to need to re-calibrate this often? The app says once every 4 months.


No, that is not normal. I would submit a ticket. How much of bottles one and two have been used?

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support ticket sent

I ph my water to 6 every time I fill however it still seems like its using a whole lot of acid. Been thinking about ph to 5.9 instead since the PH keeps jumping.

My first grow didnt work out and I did have to do an emergency drain / fill due to a ice bottle leak (been trying to keep temps down until my chiller arrives). However i don think it should be needing to balance the PH so much.

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Are you using any other additives?

I am using hydroguard 5ml
And b52 at 1/4 strength to lower the stress level until the chiller arrives it’s been hot here and I been trying to keep the water temp to 72 by rotating iced water bottles .

I’ve noticed the ph jump since my last grow attempt before any additives

I believed I asked you before as well. Since then, this is my 3rd calibration

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The fact that it keeps prompting you to calibrate certainly seems off. I would su Have you researched the effects your additives have on pH? Has support responded to your ticket?

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Yes, Danielle responded and told me to pull B-52 and not to PH the water prior to putting it into the grobo as it can raise the PPM, causing the EC sensors to shut off bottles 1 and 2 from dispensing anymore and correcting the PH.

They also had me do a drain / fill so that they can check the backend for the PH changes. They did not think its the probe faulty.

Also to combat the nute burns, I should add 1-2 cups of RO water into the reservoir in between dran/fills

The ball is now on their court, waiting for a response. Grobo does have a pretty good support service I must say.

@SWSVIC since were not supposed to be filling the grobo with the additives, how do you add your additives? I read somewhere you do some sort of injection, very interested.


When adding water to reservoir (“topping off”), just run the Grobo fill protocol with a bucket of RO or Distilled water as you would if you were conducting a water change.

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Yes, I do inject my additives into a tube that is connected to the outgoing flow of my water chiller plumbing after the grobo dispenses it’s nutrients, cal-mag, and pH. It is specific to my set up. You can get long syringes and just inject them directly into the reservoir however, the grobo does the same with our nutrients.


What’s Crackin SW​:facepunch:t4::blush:

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What’s up brother :call_me_hand::call_me_hand:

Got me some lacewings to just keep things cool in plant Ville

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Just a FYI Water Temp will have a factor on PH. You maybe jumping your PH around by your temp going up and down

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Thank you @Mpower11, that makes sense since were supposed to PH our water 25c

I am still confused to why the PH Probes would prompt to re-calibrate. my home temp is 78f
All I got from Grobo support is that I shouldn’t use B-52 or any additives.

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Do you have a Ph meter to double check what the ph of the res is?

Based on that information you can tell if your ph probe is doing the right job in Grobo

You should be around 5.8 to 6.2

You can also double check your Ec at the same time if you have a Ec meter

After my drain fill yesterday, it looks like the PH is now at 6.2 (I checked just now)
The PPM is at 435. According to the GH chart, I should be around 350-450 PPM for week 1 growth so I am within range without any additives (grobo nutes only). Strange that I am seeing a new nute burn spot on one of the leaves.


Looks like Grobo ph probe is working correctly based on your sample. Are you using tap water or Ro?

Tap water will use more acid than Ro

As far as the recalibrate 4 times in a month I’m not sure why but you shouldn’t need to do that.

I am using RO water. At the moment all I’m adding is Hydroguard 5ml.
I’m hoping when I do my health check tomorrow, it wont ask me to re-calibrate again (I’ve been doing a health check once per week)

If it was me I would do this (this is a totally different thought process so don’t take it the wrong way please)

Skip doing the health check and get a good digital Ec/ph combo meter (faster etc than drip kit)

Do a daily ph check of your reservoir and then you know if your Grobo is doing the right job or not. Plus this gives you the added benefit of knowing you have a problem with your pH in your Grobo before the plant tells you have a problem big bonus

I wouldn’t overthink it until you verify that you actually have a problem


Thanks, I have been eyeing the bluelabs combo meter however was holding out a bit since I went pretty ham on my initial grobo purchase and accessories.

In the mean time, I tossed out a cheap china PH meter I was using and been using the drip test.
I placed an order for a Dr. Meter pen just now (seems to have good reviews and affordable).