Water sitting out - does pH change?

[hlmbrwng]

I would like to prepare my mash and sparge water tonight, so as to have one less thing to do tomorrow. If I adjust the pH tonight and let sit overnight, will this affect the pH?

I would also like to keep the lid off to let chlorine escape. I will probably also add a campden tablet for that just to be safe.

I could always adjust mineral content (campden tablet included), let sit overnight, then adjust the pH tomorrow. It's just that sometimes it's frustrating getting the pH right. But I think much of that has to do with a broken pH meter...just got a new one, freshly calibrated. (now i'm just babbling)

 

[cswis86]

I don't think there's any reason that the pH should change overnight. I always treat my water the night before. Just make sure to measure your mash pH so if it doesn't hit your target pH you can adjust it.

 

[MrHadack]

Actually, it will change slightly. CO2 is absorbed by water which will cause the pH to go down a bit. How much depends how long it sits out, I suppose. Also, if the water contains chlorine, that will escape over time and cause the Ph to go up. Again, it could just be a point or two, but that's enough of a change to be concerned, perhaps.