rdwc ph issues

[funkybud]

i'm running a 16 bucket rdwc hydro system. my ph drops in a day,from in the 6's to 5.2.
i adjusted with ph up last night to 6.8,today i checked again.there at 4.7ph.
air pump are 45 lpm? active aqua pumps 1 for every 8 buckets.
310 gph water pump to circulate nutes to the 16 buckets.
all the buckets are covered with duct insulation including return lines,which are covered with pipe insulation wrap.the water never rises above 65 degrees f.
room temp stays at 77 degrees,with rh at 35-45%.
no pests have been found,on leaves or under the 10 inch bucket tops.
ppm stays at 850 [approx] started at 950.
i'm running advanced nutrients hobby grower package.
i'm at a loss. please help me fill in the blanks as to what is causing this.

 

[newmexgrow]

Hiya, I'm running my first rdwc system and also, but I'll a few things I've picked up along the way to share.

1-water. Where's it coming from..what's it treated ( before ferts) PH/PPM numbers (what are you using for a meter?) My water is coming in at around 7 or so with 80ppm..which is good as the water is hard and unfiltered ( RO system) it's hovering around 850!
2-grow media...hydron needs to be cleaned really really well..it's been said to cause PH swings if it isn't. I played it safe
3-Accurate measuring. I opted for the milwalkee ph/ppm meter..kinda pricey, but i know when it comes to tools..you pretty much get what you pay for and I don't think I'll use a cheapo meter ever..too much at risk.
4-hoses?..there' s some really bad ( outgassing) hose out there..has letters printed on it. Think it's a sticky.

You seem to have air and pumpage under control...temps too.

how big is your res?

i use technaflora and find my ph is going _up_ all the time..manageable..and predictable now that I'm in progress.

I think 6.8 is a bit too high..check out blazeones numbers for schedules 5-5.5 is target..but I follow his numbers..for my first rdwc

Using a little cal mag and sugar daddy additives..didn't see much cal problems..our water is still pretty hard..even after treatment.


Oh yeah...when was the last time you filled your system?

 

[funkybud]

1 tap water at 160-170 ppm,ph at 6.5
2.hydroton. cleaned reallywell. no ph swings untill 2 weeks ago. 4weeks into flower with 4weeks vedge.
3.hanna ph pen,calibrated with 4 and 7 solutions,replaced batteries and recheck with gh ph testing solution.
4. general hydroponics 1/2 and 1/4 inch hose.
rez 40 gallon capacity.
i raised the ph to 6.8 knowing the ph would drop,but untill recently this has been happening.ussually i add about 2 ml of down and keep it at 5.8-6.2,as soon as it would hit 6.5 i would add down to the top off water,which would take it to 5.5,and bring the rez up to between 5.6 and 6.2.
flush and fill every week,on saterday. top off during the week with ph adjusted tap water.

 

[funkybud]

air movement- 670 cfm exhaust fan runs continuosly,circulation fan runs when lights are on.air is always exchanging.

 

[Chris1]

Dilute your solution a little until you can get ph under control

 

[budshoteyes]

I agree with criss1
I've read often that advanced nuts recommendations are way to strong
What stage of grow are your plants in...early veg ?

And isn't the hobby package from advanced nuts supposed to be PH perfect?....if not,maybe you have an old batch of nutes gone bad?

 

[PuReKnOwLeDgE]

^^^ Yeah what stage?

clones= 250-450ppm @ .5 usually 350 for me. This last the first 10-14 days while roots establish. Once the plants take off I knock up to 550ppm, late veg 650-700, stretch 700-800, Day 14 flower switch to flower nutes 750-800 mid flower 850-1000ppm. That is the ranges I normally see after years of growing in RDWC.

When PH drops it usually means your feeding to high, or you have some rot issues.

ph down feed less ph up feed more until you balance it. I can leave my rdwc room for 3 days no auto top off and the numbers are the same as 72 hours ago.

Here is tonight:

 

[funkybud]

the plants are 4 weeks into flower.

 

[Scrogerman]

PK is prolly right, thats a dialed system right there!. PH drop usually indicates nutes too hot. It can also mean you have a bacterial infection & anerobic conditions but that is unlikely judging by the amount of air your pumping through your buckets & your res temps. im with PK on this one! drop your EC a bit & watch your PH(&EC) over 24 hours, keep adjusting untill it settles down.

(Nutes)
PH Down, EC Up = Too Hot#
PH Up, EC Down = Too Lean#
Stable PH & EC = balance & happy plants. I like to keep it slightly lean, so my PH rises 0.3-0.5 over 2-3 days. Its better to keep it slightly lean than slightly hot bro! Chart your PH & EC & you will be able to see/hear what your plants require.

G'Luck!

 

[stoney917]

pk said it first my brain goes right to rot when ec and ph go in same direction. as scroger said rule of thumb is ph up ec down which is my preferred method i mix my nutes they set my ph at bout 5.2/5.5 and i let it drift up to 6.2 6.4 if im lazywhich is bout 2 days then when i top up with ph water its all good for 2 days.... but since urs are goin in the same directions u dont have a feed issue most likeliy rot issue but ur tempts still got me thinkn...hmm see what others have to say..

 

[funkybud]

i'm starting to think either rot,or bad nutes.
last night i drained half the rez and refilled with straight water.ph still down low,4.5 -5.0.
i added a diiferent nute,esu greenleaves. leveled the rez out at 6.5 i know that was high,but i figured if it was going to drop anyway.....
also added 200ml of h2o2 to the 40 gallon rez.
now the ph is at 6.7 just checked it.840ppm.
we'll see what its like tomorrow night,up or down.
thanks for all your help,i quess i will know more tomorrow.

 

[Rusty Shaklford]

Sweet

Sweet

^^^ Yeah what stage?

clones= 250-450ppm @ .5 usually 350 for me. This last the first 10-14 days while roots establish. Once the plants take off I knock up to 550ppm, late veg 650-700, stretch 700-800, Day 14 flower switch to flower nutes 750-800 mid flower 850-1000ppm. That is the ranges I normally see after years of growing in RDWC.

When PH drops it usually means your feeding to high, or you have some rot issues.

ph down feed less ph up feed more until you balance it. I can leave my rdwc room for 3 days no auto top off and the numbers are the same as 72 hours ago.

Here is tonight:

Man those Indicas look sweet. I backed off the heavy Indica stuff myself as the big fans blocked to much light.
What size res are you running? I have since switched mine to a duel set up which holds holds about 60 gallons and I am wondering if i need a bigger res? My 20 @ 3.5 per is 70 gallons in the buckets. looks like you have about 30 and was curious. Here is my last set up but have since changed it out for the bigger 1" return line.
Password 666666
http://vimeo.com/20776316

 

[Dr.Greenthmb420]

Did anyone care to ask if you CHECKED YOUR PH METER OR YOUR TDS METER! I spent 200.00 on a Hanna and Didnt know it was reading 1 whole PH point different. Calibrating was not successful. I should have returned it when i had the chance. Hope you find a simple solution.

 

[petemoss]

1 tap water at 160-170 ppm,ph at 6.5
...
i raised the ph to 6.8 knowing the ph would drop,but untill recently this has been happening.ussually i add about 2 ml of down and keep it at 5.8-6.2,as soon as it would hit 6.5 i would add down to the top off water,which would take it to 5.5,and bring the rez up to between 5.6 and 6.2.
...

I take it you raise the ph to 6.8 with Ph Up, then add Ph Down and Ph Down again in the top-off water. I've always heard that it's not good to add Ph Up and Ph Down to the same nute mix because it raises your EC and screws up the buffering of your nutes.

Why not mix the original batch with un-Ph'ed water and use less than half of the recommended dose (AN suggested strength is too strong). That way you should be starting with a higher ph. When you add nutes, the Ph should drop. Leave it alone for a couple of days and let the buffers kick in. Once the Ph has stabilized, make your first Ph adjustment if needed. If you don't "chase" your Ph, you should get less violent Ph swings.

IMO less than 65F water temp is too low. Below 65, root growth tends to stall in DWC. Try setting water temp to 68F and see if growth is better. And as others have suggested, your meter may be bad. Can you verify your meter readings with Ph drops?

 

[tjo]

i had and i have the same problem..
H2O2 is your friend..use some and you will find that PH level
much stable than before...

 

[Scrogerman]

I always make sure im packing a full spectrum liquid PH test kit, that way i can test it against my PH meter at PH6.0, which is Yellow(only). I know my PH meter is working properly then.
Good info from the other guys here too. rootzone should be set to 68f, 65f is the absolute minimum, roots dont like to be kept to cold. Dont mix PH up & down in the same solution, im pretty sure it causes precipitation, iirc solution goes cloudy immediately, not good. use un'phed solution/water for your PH up, if you add too much down, no probs then. The H2o2 is always a good idea imo. Hope this problem settles down for you. Some pics would be good!
G'luck man!

 

[funkybud]

thanks for all comments. i was not using both up and down in the same soup change.
when these plants were growing well,i would have to add the raise to keep ph in check.
2 weeks ago when i started to notice the ph dropping like crazy,i started to add the up to get in check.
i added once to a solution that had raise in it,then found the next day lower also.that day i changed the soup.i figured something was up.
that rez change nothing had to be added.nothing had to be added for 2-3 days,then the rez dropped again.thats when i started to add the raise to the rez.
2 nights ago i drained half the nutes and replaced with tap.the ph was still low,in the high 4 to low 5's. i added raise to get the ph up,and added a different nute to see if the ph would stay up.that is also when i added the 200ml of h2o2.as of last night the ph was still up in the 6's.

i do have the general hydroponics ph drops;the kit you get a container for the water,and the drops to put in it.i have used it and both the digital tester and the drops were the same ph.
thanks to all who has helped already.

 

[Sgt.Stedenko]

Alkalinity os a measure of the solution's ability to buffer additions of acids or bases.
Low alkalinity will allow for greater swings of your pH. Adding acids (pH down) will decrease alkalinity. Baking soda will increase alkalinity, but I wouldn't recommend it for a hydro solution.
Tap water is your friend here, since it has a higher alkalinity than RO or distilled.
850 ppm may be too high for the strain you're growing. Like others have said, drop the EC to see if pH is more stable.
I doubt it's the AN.

 

[bickeyb]

have you checked to see if there is any rot? i use A/N and i always found if my ph starts to drop, rather then raise, i raise my ppms up.. even if i start to get nute burn the ph goes up.. i think your under feeding,, at 4 weeks flower im usually at around 1100-1400 ppms,, and you said they had a 4 week veg,, they have to be huge.!

 

[funkybud]

have you checked to see if there is any rot? i use A/N and i always found if my ph starts to drop, rather then raise, i raise my ppms up.. even if i start to get nute burn the ph goes up.. i think your under feeding,, at 4 weeks flower im usually at around 1100-1400 ppms,, and you said they had a 4 week veg,, they have to be huge.!

you are correct. they are huge! about 4 foot tall when going into flower,now there about 5 foot.

i have tried a single water farm that i had modified with 2 air pumps from a pet store. that system i also used a/n nutes hobby package as per the directions. those 2 plants would eat all nutes added from week to week.fresh batch was at 1200ppm,by the time i changed out the rez again,they were at 400ppm.these 2 plants yielded a pound of great meds.