Rdwc water insert

Ok so I have a 12 site bubble flow rdwc. I am a newb constructing a tent set up and I am about to start testing the water. They are 6.5 gallon recirculation buckets which are attached to a 25 gallon reservoir.

I Will be purchasing a external water transfer pump so my question is how do I measure the amount of water being filled or do I just eye ball it and allow gravity to take course?? Also how do I ph the water before I transfer it?? Would that be possible from the sink?

Dont have RO system so I'm using the tap and trying to do it right and test first before I plant. Any advice appreciated. Peace

Can you install a water shut off valve? You could fill, mix, and adjust ph in the main reservoir; then open the valve and the res would drain into the buckets?

Or purchase a 55 gal drum, mix in there and transfer to the rdwc system maybe?

Just brain storming

Oh well from bottom line to the reservoir there is a valve to stop the flow of water. As far as the 55 gallon idea Hell yea good idea. I do have another 25 gallon res but I know ill need more water than that or am I wrong? As far as the set up is concerned what would u suggest as amount of water to be ran consistently for a 12 site system??