water and pH

here is my problem:
i prepare my nutrient solution and adjust the pH to 5,5, and on the next day, when i mesure the pH again, it's up to 6 something, the day after that it's 7, a few days later it's back to 8.
someone told me that it could be because tap water is highly buffered, so i tried with mineral water.... and the pH is STILL going up after i've adjusted it.
i have no idea why it's doing that, or how to fix it, and my plants are dying..............PLEASE HELP!!!!

How big is your reservoir? Smaller reservoirs suffer from a higher level of Ph drift than smaller reservoirs do.

The pH in the nute solution "Rebounds" because of all of the nutrients.
try and use distilled water. it has 0 ppm Ph 7.0
don't worry about the Ph if it doesn't stay at ph 5.6
day 1 ph 5.6
day 2 ph 6.1
day 3 ph 6.5 <----Adjust your Ph to 5.6

i read somewhere that distilled water is bad for the plants tho? are you sure i can use it? and do i mix it with tap water or something......?

Don't forget to account for evaporation. That may effect pH as well. Try adding some plain water back to the rez and check pH again.
Distilled water is all I use and will be fine.

I have a similar problem. My PH just keeps going up. I add PH down almost every day. My plants seem fine though.

snej said:

i read somewhere that distilled water is bad for the plants tho? are you sure i can use it? and do i mix it with tap water or something......?

Click to expand...

I used RO/DI water for seedlings one time. I've since decided that any water that touches a plant should be at around a min of 200ppm.
I've read that DI water can literally leach chemicals and ions from plants/medium... I'm not sure about distilled water, though.
I don't mix with tap water (that would be counterproductive to filtering it), I just make a super lite nute mix.
One thing that I know for sure is that 0ppm water is nearly impossible to keep PH stabilized. It runs all over the board. Adjust it to 200ppm, and it's not so bad. Maybe this is where the ant-distilled water thought came from?

what is the growing media? hydroton with rockwool or something similar? I would leech (just soak or pour large amounts of clean fresh water over the media) and then put some tap water in a bucket and let it sit for a couple of days .. then add your nutrients (one component at a time) .. mix.. wait a couple hours.. then add it to your freshly leeched hyroponic system.. I had a similar problem with this one hydro setup I had a couple years ago and I started spritzing (word?) some lemon juice over the media each time I changed the nutrient water, and it kind of acts as a time release acidifier (word?) which brings the ph back down over time (to compensate).. its a weird problem tho... good luck