water them slowly, I have a 2 liter sprayer, and the way I water my 10 gal pot is, I spray like 500 ml of water, then wait, then another 500 ml, then wait, and so on. I stop once I see run off come out of the pot. It's a slow process but if you are not in a hurry I think its a good way to do it.
Usually you dont want any run off while you are growing organic, but im just getting the hang of it, and im not sure how much water can my pots take.