huge swing in pH, what could be causing this?

[stucklikechuck]

a brief intro:

i am running a recirculating system using 6" rockwool cubes. i have 35 plants in a 4'x8' table with a built in 40 gallon resevoir. i am using cutting edge solution nutes with the following additives: uncle john, mag amp, plant amp, sweet, hygrozime, Van De Zwaan Roots Excelurator. i have a res chiller and a co2 setup. i have 2x1000w MH bulbs in a cooltube and a light mover. water temp is 66-68 and room temp is 76-78 (78-86 with co2 enrichment). i do a weekly res change on sundays and this is my 2nd week of vegging. i was using 50% nutes (33% on the van de zwaan) and for the second week bumped it to 75% nutes with 50% on van de zwaan.

i use tap water which is 7.0 and 80ppm which has been sitting for 24hrs and i add my nutes and pH to 5.5.

here is my problem:
i checked the pH yesterday (Thursday) and it jumped to 6.8. i dumped the nutes out of the res and adjusted the pH to 5.5 and put the nute water back in. today i checked it and the pH was 4.7! i am pretty sure my hana combo pH ppm meter is accurate as i calibrated it 3 times yesterday and once today. can someone help me out please? thanks!!!!!

 

[Earl]

Your pH will never stabilize using tapwater.

Switch to RO or your grow will be poor.

 

[KirklandsFinest08]

whats ro agian?

 

[Twistyman]

Reverse osmosis....available at Wal*Mart..

 

[Earl]

You need to invest in an RO machine.

Store bought RO is 59-99 cents per gallon.

Home made RO is 9-10¢ per gl

 

[shenagen]

Tap water that comes out at 80 ppm and ph 7 does NOT need an RO machine...yes they are the best...but thats a very nice tap ppm...most would kill for theirs to be that low. My tap is at 130-140 and my ph is stable after the 3rd day. And dam earl you've become an RO henchman!!....saying his grow will be poor without RO is just silly! But if you have the extra cash...I'd get one..moneys too tight for me to justify it.
As far as the swing in ph goes...why did you take the nutes out of the res.? Sometimes when I'm adding ph down to the res. and I don't let it mix up well enough before re-testing, I end up adding too much and the ph is too low. Could it be that going on? Since you have a res chiller it rules out bad bact. in the res making the ph too high. Welp..thats my 2 cents

 

[toast master]

Hey Stuck..... i use H & G nutes and like them fine .. root excel will drive up the ph up for a few hours then should settle down after that... the reason h&g did not want you to oxygenate was the added enzymes to help pathegens under control , but i think they have changed that,... its ok to oxy them ... my well water is 450 ppm out of the tap.... raised 2 kids horses, pigs, chickens on it I think i can grow pot with it just fine.. no fancy ro for me... good luck

 

[Al B. Fuct]

Your pH will never stabilize using tapwater.

Switch to RO or your grow will be poor.

Absolutely false. I really wish you'd stop propagating this myth, Earl. You've done it in several places on RIU. You're allowed to fool yourself but you're NOT allowed to fool others.

I've run nothing but tapwater for more than 20 years. My pH stays dead steady after mixing a tank. There's lots of causes for wandering pH but tapwater isn't one of them.

Please point out the tapwater damage to these plants! Where's it all going wrong for me?

(click img for full size)



















This cherry tomato plant growing in soil in my organic veg patch is for those who insist that chlorination will kill beneficial microbes in soil. This plant yielded more than 450 fruit- on evil, evil tapwater out of the garden hose. Chlorination is in fact the indoor growers' friend. It suppresses pathogens while the water is in the pipes on the way to you and also for a couple of days in an open nute tank until the chlorine evaporates. After that, you must use a pathogen suppressor like H2O2.

A lot of people complain about a high ppm reading on their tapwater. Guess what? That's caused mainly by dissolved Ca & Mg, which the plant needs anyway and which you must replace if you remove it with RO or use distilled water.

Any water you can safely drink will grow fine plants.

 

[Earl]

I apologize for my remarks
evidently my tapwater is poison.
I'm glad yours is OK
I will shut up now
see ya

 

[toast master]

I hate when the teacher chewes me out ... al makes me stand in the corner with the dunce cap.. lol

 

[stucklikechuck]

i got a gallon of ro water today (33cents/gal) and pH is 8.0 and ppm 003! i will try this out and see if i see any differences. otherwise, i will stick with my tap water.

 

[Al B. Fuct]

Using a gallon of RO water isn't going to prove much. That'll be a tiny fraction of the water used in the life of the plant. You won't have enough to even leach the nutes our of your media. It's certainly not going to sort out your pH problem.

One of the most common causes of pH wandering is pathogen activity in the roots- and I suspect that's the case here. Treat the nute soln with 50% grade H2O2 @ 1ml/L every 3-4 days. Set your nute soln pH at 5.8, nutes at 1400ppm.

Pare down your huge array of magic sauces to just nutes, H2O2 as specified and pH correction. Set your pH after adding nutes- many nute mixes include pH buffers and will set 8.1 tapwater to 5.8-5.9 with no intervention with pHDown.

I really want to know where this grand conspiracy regarding evil tapwater came from. Truth is, water from a modern municipal water treatment plant is completely fine for plants, in soil or hydroponics. I've grown cannabis on 2 continents, in Aus and in the midwestern USA, which has some of the hardest water you can find on the planet. Never had a problem with municipal water.

Moreover, instead of complaining about how bad your water is- and in most cases, with no real idea of what really IS in it... FIND OUT what's in it! Your local water util might publish water quality data on their website or you can request a copy of their recent analyses.

Again, if you can drink it, you can grow great plants with it.

 

[stucklikechuck]

oh yeah, i wasnt going to add just that 1 gallon, i got that just to see what kind of ph and ppm it had. i have no qualms about the tap water here, i think its some of the best in continental usa. if this ro doesnt work out im goona go with the route you recommend, but i want to try everything so i can learn on my own trial and error.

 

[Al B. Fuct]

heh, well, you now know, given the 3ppm figure, that water with no minerals is not very conductive! I'm a bit interested in the 8.1pH, that seems a bit alkaline for plain water, I'd have expected 7.0.

I also have a degree in Cannabis Cultivation from the University of Trial and Error, so I appreciate your desire to work it out yourself.

 

[slump]

Here's Chuck's water:

Alkalinity, bicarbonate (mg/L as CaCO3) 27-40.4
Alkalinity, carbonate (mg/L as CaCO3) 1-1.2
Calcium (mg/L) 4-13
Hardness (mg/L as CaCO3) 16-44
Magnesium (mg/L) 0.9-3.3
Potassium (mg/L) 0.5-1.0
Silica (mg/L) 9.4-12.0
Sodium (mg/L) 5.6-12

There's an uber report here if you think it will help. We're in the orange column on the charts.

Since the big dip down on Thursday the pH has risen back up to 5.7 today. PPMS are just over 1350.

Just really curious as to why it dropped that day when the reservoir before it had no problem.

EDIT: From what I understand RO water's pH is dependent on the source. Distilled water would be the only water you could get a natural pH out of. Summed up pretty well here.

 

[Al B. Fuct]

Chuck's water looks an awful lot like everyone's else in the US, except for the mudwest, where there's generally more Ca, Mg and Fe found in tapwater due to alluvial, largely limestone catchments. Coastal areas of the US tend to have sandier catchments, so there's more silica and less Ca & Mg.

Summed up pretty well here.

yep, seems that RO doesn't remove dissolved gases, accounting for the alkaline reading. Interesting stuff.

 

[DR. VonDankenstine]

AL-those plants look healthy and green. My problem is that my tap water comes out at 710-760 ppm's so I use R/O water. Your 100ppm tap water is lower than 90% of bottle water(your tap water is basically a micro nutrient additive)-If I had 100ppm tap water I would use it straight of the nip smiling all the way to reservoirs-I tried every way possible,even went with a separate, individual--n/p/k only nutes and still had problems. Never had a ph problem. Since I went with the R/O I haven't had a problem. I use the tap water for my outside plants without a problem but ground soil has a way of buffering and adjusting most things you throw at it. Hope things are well brother-I posted a question on your tstat thread.

 

[atrumblood]

dude, Al B. Looks like you have a kick ass garden outside. (God I wish I had the space to have a garden like that.)

 

[Al B. Fuct]

AL-those plants look healthy and green. My problem is that my tap water comes out at 710-760 ppm's so I use R/O water. Your 100ppm tap water is lower than 90% of bottle water(your tap water is basically a micro nutrient additive)-If I had 100ppm tap water I would use it straight of the nip smiling all the way to reservoirs-I tried every way possible,even went with a separate, individual--n/p/k only nutes and still had problems. Never had a ph problem. Since I went with the R/O I haven't had a problem.

You have municipal water or are you on a bore? I really wonder what's driving your tap ppm to 760. Seen an analysis of your water? If on muni water, you might look on that util's website for recent analyses.

Hope things are well brother-I posted a question on your tstat thread.

Yep, we're OK here (except for a shitty ADSL line, I'm offline 30 mins of every hour at this moment). I did reply to your query about the tstat.

dude, Al B. Looks like you have a kick ass garden outside. (God I wish I had the space to have a garden like that.)

Yep, the veg patch is a great bit o' fun. Moreover, it eats the composted trimming waste from the grow op. I did not have a decent veg patch for a long time, but I DID grow lots of herbs & veg in containers on the verandah. Container growing can be just as much fun as a big patch in the yard.

 

[slump]

I think we pinned down the huge swing in pH.

First off the table is a Fearless Gardener

I didn't like the table after the first res change and despise it even more now but it is what it is and we'll roll with it for now. The thing is the table has two 3 inch deep channels that run the length of the table and are constantly filled with water from the res below...the water don't hit the plants till the air pump is turned on then the table floods...pump goes off the water heads back down in to the built in res. But the ALGAE build up in these channels was pretty significant at one point last week.

"As a consequence of photosynthesis the plants utilize carbon dioxide in the day time and remove this from the water causing alkaline carbonates and bicarbonates to predominate in the water and the pH to rise. In the case of heavy algae blooms, the pH of the water can fluctuate quite dramatically through a 24 hour period"

When the spike up in the pH was noticed...we pH the water down...and then the effects from the algae bloom subside...we're bent over with the 4.7 pH'd water. Fortunately our canopy has now shaded the channels (for the most part) and I'm planning to cover them up completely tomorrow.

From what I understand, h2o2 does a pretty decent job of genocide on the algae? Is this true?

Thanks in advance.