PH Dropping quickly?

You could be right Mr E, my water is well water so there is probably a big difference between that and tap water....you could add an entire bottle of ph down and it would only hold it for a day or two before crawling back up....
I do find that when I first do a res change it takes, as you say, very little but does not stay very stable for the first day or so until I have added more ph down etc, then it seems to stay pretty much where I put it about 48 hours in. Now flowering is a different story with the ph probs

I use baking soda as ph up usually as I only have to use small amounts and it's easier than ph up for me....I doubt I would use it if I had to raise the ph a few points or so....or have to use it often but I have not had any problems using it so far....keep it on hand with my other crowd of bottles. I have found it raises ph kind of slowly over a few minutes so I add a little and then check it a few mins later because the number seems to rise a little more after a min or two. I don't seem to have that particular situation when using ph up/down so just a a heads up.

Well also, the nutes have ph buffers in them, so theoretically a nute solution SHOULD hold it's ph level more stable than plain RO water (or any low ppm water).

Baking soda not only raises ph, it supposedly also has a buffering effect. So it COULD be a possible better choice for me (or supplement) since my RO water seems to be very very unstable.

I had to PH Up my res twice today in fact, and "chasing ph" is suppose to be bad for the plants. After the second dosing, I added about a quart of tap water and the ph rose a couple of more tenths to 6.2. That was 2.5 hours ago and I'm currently looking at 5.9.

Kinda driving me nuts obviously. I have 6 or 7 gallons of plain water on hand, so I may go ahead and mix up a batch of bloom nutes later tonight/tomorrow morning and do a quick drain and fill of the system again. Using some tap water as well.

I've got to get these blooming, they're starting to reek pretty seriously and they're just dying to load up with flowers.. not a good time for me to be goofing around with experiments. But it seems there's no single simple answer, so there we are.

Well I hope latewood or somebody hops in with an answer cause now it's bugging me too!

Well the baking soda SEEMS to have done the trick! I took about half a teaspoon and mixed it with a few tablespoons of water and stirred it a bit and dribbled in a SMALL amount. My ph went up, but it's STAYing up is the important thing.

I believe the article I read on icmag was correct, about it acting as a PH buffer.
It went up quickly, and in fact I'm about to go Down it, lmao.

Res change tomorrow with any ph up adjustments using baking soda and a prayer ;)

Good luck.....update!

PH was exactly the same this morning as it was last night, so it looks like the buffering was what I needed.

Ok, today I did a nearly full res change. I left about 2 gallons in there. I used a slightly weak lucas bloom formula with about 8 gallons of RO water. (I used a formula for 7 gallons when I have a 10 gallon system). Poor plants have been through alot, so I'll see how they behave.

After it had circulated awhile and I adjusted the water level, I ph up'd using a few ml's of the baking soda and water. It took very little, and I'm currently sitting at 5.7PH, 650PPM.

I had trouble with ppms at that number when my plants got to be about 7 weeks old and that's what caused the deficency in my last grow....keep a careful eye....

5.7 and 640ppm now. Looks like so far anyway the ph is nice and stable.

I watch them all day long pretty much, so no trouble there. I had trouble a couple of weeks ago when I had stronger nutes, so I'd rather go light than too strong.

5.8 and 620ppm. Looks like everything is working, my plants are taking up nutes and hopefully well on their way to a healthy flower cycle.
Now we know what to suggest if others ever run into the same problem and have beat their head against the wall trying to figure it out.

Thank god....never knew the baking soda I was using did that....