Why does the PH in my water go up overnight?

[Allotrope1000]

Lots of factors will affect the pH of your water or nutrient solutions - temperature swings, source water chemistry, products you intentionally dissolve, etc. Also, time setting around pre-mixed in a bucket. All the dissolved ions are constantly inter-reacting trying to obtain an equilibrium state in your solutions.
The faster you use your solution after mixing gives it less time to change pH.
Given the above, I noticed my pH's rising over time spent sitting to be used. It is easy to check pH with your meter or test strips. You might originally adjust your solutions down to pH 5.5-5.7 and let climb up to 6.5 ish before lowering again. That pH swing of about one point covers the optimum range for various nutrient uptake.

I run 12 AF plants in 50/50 coco/perlite in 7gal fabric pots in a polytunnel greenhouse during the winter months.

 

[Allenpro]

The lesson in all this is dont setup an automated system and walk away without observing it for a while, like the week before you leave. Hindsite of course but been there done that

 

[Allenpro]

I think I get it now, hydro growers are monitoring the PH of the media (water in the reservoir) 24/7 . With soil you cant do that as easily because the water/nute mix can change when its added to the soil so thats why you do the "slurry" to find out what the media PH level is at. Is that about right? Did this blind hog stumble upon an acorn?

I never understood checking runoff PH before, it always reminded me of an how an old farmer checked to see if the cows were getting enough salt.

 

[Wayzee]

Yep and the soil pH can slowly build up over time if the water you're using has slightly high pH especially if you're not watering to the point of run off.
Haha that just reminds me of the 2 weeks work I done at a dairy farm... Yea na not for me, thanks for the opportunity though. Hahaha

 

[Allenpro]

The only time I want to see a cow is on the butchers counter

 

[dirtymike]

hence the numerous salt blocks next to the watering trough.