ph seems to rise as H2O sits

so, i've been letting my tap-water sit for a couple of days like a good little scout, to get rid of any chlorine before i use it on my plants

HOWEVER...

i bought a pool ph test kit, and tested the water that was sitting out. there seemed to be no measurable amount of chlorine, but the ph was through the f-ing roof!!

out of curiosity, i tested some water as soon as it came out of the tap. not only was there no indication of chlorine, but the ph seems to be dead on 6.8!!

anyone have an explanation for this? freaky...

what type of medium are you using? if its rockwool that will cause your ph to rise if u don't rinse it properly. And also you will find to have to deal with rising ph in the first 2-3 wks of flowering after that you'll see that the ph will be more stable.

wafflehouselover said:

what type of medium are you using? if its rockwool that will cause your ph to rise if u don't rinse it properly. And also you will find to have to deal with rising ph in the first 2-3 wks of flowering after that you'll see that the ph will be more stable.

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thanks for the reply- i'm using soil, but actually, i tested the ph of the water before i used it on the soil, so the reading is just of the water before being used on the plants. it seems that as the water passively sits in an open container, the ph level rises... maybe there are particals of some sort in the air that are settling onto the water and causing the ph to rise?

its the metal solids in your tap water. How high does it rise after being ph corrected and days?

Theres certain chemicals in your water, everywhere puts them in.

Water has a ph because of its content, if you shove in some acid its going to drop and likewise raise for an alkaline.

When the water or the minerals in it or any part of the water changes i.e. a part is removed the ph can swing.

So say you have 4 plants in a hydro system and the nutes are good and the water is good and the ph is good. The next day the plants take more water than nutes, that will mean the concentration of the nutes has changed so the ph could be different because its a slightly different solution.

This could apply to your situation with having left the water out a certain amount has evaporated and the minerals in the water are still the same which could alter the ph or maybe certain chemicals in the water have dispersed and this has altered the ph.

wafflehouselover said:

its the metal solids in your tap water. How high does it rise after being ph corrected and days?

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for now, i'm using cold water directly out of my tap- the ph is at 6.8 straight out of the tap, and there's no measurable chlorine (for now- that could fluctuate, so i'll keep my eyes on it)... so it seems like i don't have to deal with adjusting ph for now.

babygrow had a good point about this subject on another one of my threads, anyone that has chimed in here might be interested in seeing that post- it's helpful and shed light on what ph really is. nongreenthumb has posted some excellent info here too, thanks for that!

another benefit of not having to let my water sit (since it has no chlorine) is that it is aerated when it comes out of the spout- the longer it sits stagnantly, the less oxygenated the water becomes.

thanks everyone!

Temperature can affect pH. I know it can when you use an electronic tester. That might be because it adjusts for temperature. What kind of tester are you using? I'm not sure if temperature changes the pH of the drop-type test or litmus paper but it definitely does for electronic testers. It's probably colder when it comes out of your tap and it comes to room temperature when you let it sit so that might account for your pH difference.