PH dropping to 4.8 on my ebb and flow. WTH?

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Ganja Grower
Jul 28, 2007
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Hey all, so my girls are half way into week 5 (snocap, ak-48, and unkown that was supposed to be skunk #1, but isnt)about a week and a half ago my rez cracked and I have had to use a 15 gal bucket to flood my table. Table is 4 x 4 and full of hydroton. 15 girls in a 1in square rockwool and 6in net pot. I'm using FF cuz I still have some from dirt grows and my rez temps ride between 65-70. PPM this week I have at 1250 with about a teaspoon of epsom salt per gal. Im changing the buckets every 4th day with another 15g bucket that bubbles for at least a day in advance. I add nutes 4-5 hours prior to moving it under the table and doing the final adjusting of the ph. This has been working well till 2 nights ago the rez was at 5.0. So I put the new one in at 5.5 as i thought 5.8 is to big a jump. Hours later I come back to check and the ph is now back down to 5.2, crap so i adjust up to 5.6 this time. All seems stable while in the bucket. BUt as soon as it floods once, the ph is on the move down. I flood 1hr on 2hours off. 4 airstones on two pumps for aeration. TOnight the bucket was at 4.8. Something in my table seems like it is throwing the PH, but the are no tapes, glues, or foriegn objects of any kind that i know of or can see. I am wondering if a root condintion can cause this? ANy insight would be appreciated. Sry long post.
I would GUESS that this is happening due to the small res. Your nutes generally lower ph. If plants are drinking water faster than they are eating nutes this will leave a concentrated amount of nutes, lowering ph too much. A small res will contribute to this. Does the ph drop with the water level? Are the ppm's higher than normal when res is at 4.8?

Just a couple things to think about. Plenty more help should be along shortly.
Thnx for the response BK. I was thinking it had be something other than that simply because I ph'd the bucket to 5.7, flooded the table for as long as it took to empty the bucket (about 1 min) this was enough time to bring my PH from 5.7 to 5.6. The PPM's are up tho, from 1250 to 1290 since last night with about 2 gallons of water gone. What I have been doing at his point is topping with bubbled tap water and adjust ph. Immediatly following the next flood cycle, by PH will surely be down .2 to .3
Is sounds like you are over nuteing them. The water is being taken up faster then nutes. Also check the roots if possible for brown tips, collapsed/dry roots, or slime. Root problems can cause lockout (Ppm rise), and rot (ph drop).
Well, did a good flush from the top with H2O2, then a clearex rinse and for two days now PH has been back to my normal of 5.8. This is my first grow back to hydro, been dirt baggin for the last few years. Just gota get back into the groove of things, I think I had been over nuting and hadnt gave them a proper clean water rinse. ANyway thanx for the input guys, all is well agian.

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