You'll need a Ph test kit. General Hydroponics makes a Ph up/down with a Ph drop test in it. You can water until there is water coming out the bottom and test that water. Also are you using tap or RO water?
I already have my ph kit i jus wanted to know how to do it. For example if da ph is at 5.0 what shld i do in 3-5 gallon pots. Another ? What about if its at 7.0 should i add ph up or dwn n how much of it?
3 gallon pots- how much do i add when its at 5.0 or less? 5 gallon pots- how much do i add wen its at 7.0?
I think there's too many variables involved with this. The pH of the water, the pH of the soil, how much soil, the soil mix you're using, the strain (different strains prefer diff pH's) etc. I think you just got to try it out dude and see what works best for you.
ok here is what i do i just fill gallon jugs, then test my ph, and add ph up or down accordingly until the gallon is at 6.5. Then flush accordingly. If you need more water, fill more gallons and adjust ph every time! It takes lots of testing for me thats why an electronic ph pen tester is the shit and there like 15 bucks on ebay!