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RDWC water wont PH down

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RDWC water wont PH down

_B_ 18 Replies 4,325 Views
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_B_

_B_

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#1
Im running a 20 gallon rdwc system and after adding in nutes it won't seem to drop ph. Its stuck at 7.0-7.4. Wondering if its some sort of buffer in the nutes. Im running Masteblend 3 part salts. Tried a new bottle of ph down and still nothing. Any thoughts?
Running tap btw until RO filters come in (240ppm)
 
#2
The tap water will keep swinging because of the hydroxyl content, you can't change that. When the hydrogen exchanges in an acidic pH with nutrients the pH always returns to where it started when the hydroxyl is high. The starting pH of tap water is high to keep the water from leaching heavy metals into the drinking water. As long as you use treated water you can have problems with pH.
 
#3
Trixie said:
The tap water will keep swinging because of the hydroxyl content, you can't change that. When the hydrogen exchanges in an acidic pH with nutrients the pH always returns to where it started when the hydroxyl is high. The starting pH of tap water is high to keep the water from leaching heavy metals into the drinking water. As long as you use treated water you can have problems with pH.
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Sounds like I’ll just have to wait for the filters to come in. Appreciate it!
 
#4
_B_ said:
Im running a 20 gallon rdwc system and after adding in nutes it won't seem to drop ph. Its stuck at 7.0-7.4. Wondering if its some sort of buffer in the nutes. Im running Masteblend 3 part salts. Tried a new bottle of ph down and still nothing. Any thoughts?
Running tap btw until RO filters come in (240ppm)
Click to expand...
That’s too high for hydro.

I’d do a couple experiments to figure things out while you wait. Grab a good size container like a 1 gal cool aid jar. Fill it with a measured amount of tap water I’ll assume 1 gal.

Measure ph

While stirring add ph down until you get to 5.8. How much did you use?

Repeat this with the same amount of res water.

Now you know if it is your nutes or supply that is the issue.

You can dump that ph’ed water back in and now you can calculate how much ph down you will need for the system. Post that info up and I’ll let you know if this is normal or next steps.
 
#5
Trixie said:
The tap water will keep swinging because of the hydroxyl content, you can't change that. When the hydrogen exchanges in an acidic pH with nutrients the pH always returns to where it started when the hydroxyl is high. The starting pH of tap water is high to keep the water from leaching heavy metals into the drinking water. As long as you use treated water you can have problems with pH.
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I guess we better inform the thousands of growers out there that use tap water that it doesn’t work?

I’m sorry but this is not as complex as you are making it out to be. 2 days ago you said CO2 of 2000ppm kills plants. Flat wrong. Where are you getting all this misinformation or are you just making it up as you go?
 
#6
Coming in late and not knowing the about the specific water treatment….

Do you think that a tub of water collected then allowed to “air” would see the pH drop. I guess, Only happens if the water treatment additives are somewhat volatile.
 
#8
Correct.

I referring to any municipal added water treatment chemical(s) that when off gassed allow the pH to drift downward.
 
#10
Have no idea. I don't live in that community. Maybe someone in this vast network has experience.
 
#11
Zill said:
Have no idea. I don't live in that community. Maybe someone in this vast network has experience.
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So what COULD be in tap water that offgasses and takes PH down with it. In any community?

CO2 is virtually a given, and once out of the pipes where pressure holds it in, it will float away and cause a slight PH shift (carbonic acid)

I am not aware of any other chemicals or gases that do this that are put into a drinking water supply. But hey I'm here to learn.
 
#12
Moe.Red said:
Opposite.

Allowing offgasing of CO2 causes PH to go up.
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As I just happen to have a new 13g bucket full of fresh city tap water I can confirm after a week of sitting with half the lid open it’s gone from about PH 7.43 to PH 7.87. So it does get higher.

Does chlorine lower PH as it evaporates? Even though after C02 off gassing raises PH again.
 
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#14
Zen_Seeker said:
As I just happen to have a new 13g bucket full of fresh city tap water I can confirm after a week of sitting with half the lid open it’s gone from about PH 7.43 to PH 7.87. So it does get higher.

Does chlorine lower PH as it evaporates? Even though after C02 off gassing raises PH again.
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Actually very few municipalities use actual chlorine any more. Almost all, if using a chorine based sanitizer will opt for Chloramines specifically because they are more stable and do not evaporate like Chlorine.

Sodium Thiosulfate from the fish store, vitamin C, and a few other treatments bind it up and make it harmless. I'm not aware of any of this effecting PH tho.
 
#16
Too much aeration from air stones can cause high PH.
 
#17
After using RO water the ph seems to drop faster with less PH down used. It also stays pretty consistent.
Now I'm having trouble with brown algae buildup on the walls and stones in the system but it seems more appropriate to make another thread for help on that
 
#18
_B_ said:
After using RO water the ph seems to drop faster with less PH down used. It also stays pretty consistent.
Now I'm having trouble with brown algae buildup on the walls and stones in the system but it seems more appropriate to make another thread for help on that
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RO does not have a buffer to resist ph changes. That part is normal.

I’m gonna guess what you are seeing is diatoms. If so don’t worry they will die off once the food source is gone. Google some pics of diatoms to compare. They will not hurt anything
 
#19
Moe.Red said:
RO does not have a buffer to resist ph changes. That part is normal.

I’m gonna guess what you are seeing is diatoms. If so don’t worry they will die off once the food source is gone. Google some pics of diatoms to compare. They will not hurt anything
Click to expand...
I’ll definitely take a look. I have pictures of the slime posted on my other thread if you’re interested.
 
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