Effin A man! Tap water PH drifted almost a point after sitting out for 48 hrs.

I spent a ton of money on distilled water last grow, so Im trying to use tapwater thats been sitting out for a couple of days to mix nutes and water. I didnt know tap water PH drifted so dramatically. Fresh out of the tap its between 6.8 and 7.0. After a couple of days sitting out its 6.0

Damn! I fed my (hopefully) girls and some of them have N lockout now. I have to wait for the soil to dry to topdress more lime and feed with higher PH water.

is your tap water well water? my ph on my well water has been the exact same for the last year. through summer and winter.

What happens is CO2 fall I have your water, loses an oxygen molecule them becomes carboxylic acid lowering your ph. A 6.0 ph wouldn't cause a N so quickly at least not in soil. Was your water ph before or after mutes put in?

Before nutes. I measured the runoff and it was 5.0 after nutes, but I wasn't sure so I took my blulab pen to get calibrated at my growshop. It was off but not by that much.

How much should I ph the water to to bring it back up to 6.5?

The soil is still damp. Should I wait for it to dry out a little more before fixing the ph?

lol lucky you ^^^ my tap water comes out around 8.7 if i remember right. cant you distil your own water???
im having a similar problem in my cloner, water goes in at 5.0 after a day or so its like 6.8. im like what the hell! guess ill just have to check it and change it after a day and see if it holds.

your nutes are lowering the ph of your water. ph your solution before and after nutrients are added. when you have everything in the water, then retest it and see where your ph is. i would bet your nutes are droping the ph of the water, then it is bouncing back up. also let your solution sit for 15-30 after mixed and retest ph. nutrient solution should still be mixing and the ph will need to buffer for a minute.

Its definitely the organic nutes dropping the PH. My growstore guy just told me to keep giving it the 7.0 water and it should stabilize.