DWC PH issues: Ph dropping like a rock - Please help

John1961

Well-Known Member
@rkymtnman & @firsttimeARE - Your thoughts please.

Assuming I proceed with a RO flush tomorrow (two reservoir changes x 12 hours each), should I consider using some H2O2 during the flush to address a possible bacterial issue (if there is one)? I mean, is there a potential for damaging or hurting anything if I do a H2O2 flush without a bacterial problem present? If I use H2O2, how much should I use for 5 gallons of water?

Or should I just use plain RO water and see what happens during the flush?
 

rkymtnman

Well-Known Member
@rkymtnman & @firsttimeARE - Your thoughts please.

Assuming I proceed with a RO flush tomorrow (two reservoir changes x 12 hours each), should I consider using some H2O2 during the flush to address a possible bacterial issue (if there is one)? I mean, is there a potential for damaging or hurting anything if I do a H2O2 flush without a bacterial problem present? If I use H2O2, how much should I use for 5 gallons of water?

Or should I just use plain RO water and see what happens during the flush?
i'm personally not a fan of peroxide. it does work but it's harsh.

if it were me, do one thing at a time.
24hr RO flush first. see what happens.

if that does nothing, let's try a sterile res for a week and see what that does with your normal nute routine. call that hydro shop and see what they have as far as a chlorine root zone additive. dutchmaster zone, UC roots are 2 off the top of my head. i use HTH pool shock but you need a fairly accurate scale to do it. if you have one, i can give you the mix instructions
 

firsttimeARE

Well-Known Member
17% i was using 3ml roughly a gallon.

Its fine just dont pour it directly on the plant. And dont,get it on your skin. Burns a bit and will temporarily turn the skin white. Ask,me how,i know? Lol.

Havent used it in like 5-6 years though. I guess im just lucky cause I dont use anything. Sterile or beneficial.

Im on day 30 of my RDWC res and roots still pearly white. I probably will keep the res throughout all of flower.
 

John1961

Well-Known Member
Well, it's been 8 hours since I added 4ml of PH-Up to the reservoir to get the PH back up to 6.3 this morning.

In the past eight hours, PH has dropped to 5 2. I just added another 3ml of PH-Up to the reservoir and will give it an hour to bubble before checking PH again.

On the plus side, she is drinking plenty of water. I had to add about a half gallon to the reservoir.
 

firsttimeARE

Well-Known Member
Kick it back down to 550ppm

Thats a big rise for one day.

Bring your pH up with water and dilute it at the same time
 

John1961

Well-Known Member
Thanks, @firsttimeARE . Bear in mind this reservoir water cycle used tap water with a PPM of 180. But I'm guessing after tomorrow's RO-water flush, best case scenario is I'd start with low nutrients anyway.

I just took tonight's readings right before lights out. I'll be back in the morning with what happened overnight.
 

John1961

Well-Known Member
Good morning, folks.

Last night's PH drop was not as severe as I was expecting. Here are my morning numbers:
  • PH: Went DOWN from 6.3 to 6.1
  • PPM: Went DOWN from 690 to 660
  • EC: Went DOWN from 1.4 to 1.3
  • Water Level: Went DOWN ~1 pint
I went ahead and pumped out the reservoir and pumped in fresh RO water (nothing added). I'm gonna give the reservoir an hour or so to bubble and will then make note of my PH, PPM, and EC. I'll do the same this evening when I do another res change about 11 hours from now.

I've attached a few pics. I really think the reservoir is free of any bacteria. The air stones, tubes, and sides of the tub are as clean as the day I started this grow back in August.

7f_11a.jpg 7f_11b.jpg 7f_11c.jpg
 
Last edited:

rkymtnman

Well-Known Member
do you run your intake/exhaust 24/7 or just when lights are on?

and remind us, the plant is in bloom now, correct? for how long?
 

70's natureboy

Well-Known Member
Well, that's interesting, GH is pretty ph balanced in my experience. I also use GH in DWC and have stable PH with tap water. Sometimes i will add 1ml/gal of ph down if I'm feeding light. I usually use 5-7 ml/gal of micro and 10-15 ml/gal of bloom. a light Lucas Formula, to get me between 5-700 ppms. That chart back a couple pages said if your ph is going down your nutes are too strong.

I don't trust ph meters either. Will your meter give you a repeatable reading? Maybe something up with the tap water. Is it from a well or municipal? I guess I'm stumped so best of luck.
 

John1961

Well-Known Member
Well, here are tonight's numbers after 11 hours of bubbling away with straight RO water:
  • PH: Went DOWN to 6.3 from a reading of 6.6 this morning.
  • PPM / EC: 0 (zero)
  • Water Level: She drank a good half-gallon of water in the past 11 hours alone!
A couple of the very oldest and lowest leaves have begun curling / shriveling, suggesting that she is very hungry!

So after tonight's straight-RO flush, what should my plan be for tomorrow as far as nutrients go? I'll be using RO water from here on out. Should I shoot for a starting PPM of say 300? More? Less?

Regarding the small drop in PH. In comparison to the daily drops I was seeing when the water had nutrients in it, should I consider a different brand of nutrients? I know GH is supposed to be at the top of the game, but maybe it's just not working for my particular environment?
 

rkymtnman

Well-Known Member
She drank a good half-gallon of water in the past 11 hours alone!
i was expecting that. very good.
what should my plan be for tomorrow as far as nutrients go? I'll be using RO water from here on out. Should I shoot for a starting PPM of say 300? More? Less?
heres' what i'd do:
fill up with normal amount of RO
use 3mL micro, 6mL bloom (no grow) per gallon RO. use max dose hydroguard per gallon.

she should eat like crazy. keep us posted. if she does, we can bump up your ppm really easy.
 

John1961

Well-Known Member
Good morning, folks. Morning numbers:

PH: Remained stable overnight at 6.6.
PPM / EC: 0 (zero)
Water level: Went down less than a pint.
 
Top