I think your misunderstanding me. I want to be able to water my plants while still in my closet and not have to worry about runoff... Do you usually water your plants and let the runoff pool in your grow area? I hope not. Maybe you should fully understand a question before answering it then maybe you'll avoid looking like an ass.
With all due respect, maybe if you'd state your question clearly the first time around (let alone not stoop to name-calling) you'd get a higher quality of response.
Anyway to actually answer the question, there is more than one way to skin a cat.
The simplest (though IMO not best) thing to do is just put trays under you pots to catch the runoff. You could use cheap plastic storage totes, buckets, etc. Assuming you didn't want to move the plants, you could then use some sort of siphon/pump to suck excess water out of the trays when the runoff is complete.
The "pro" way to do it is with a runoff system. Here is one way to go about it:
-If your space is 3x3, get a 3x3 piece of plywood and line the edges with wood scrap to keep water from running off, leaving a small gap/notch in one corner as a drain.
-Then cover the whole thing with cheap plastic sheeting. Construction sheeting could work.
-Elevate the board with bricks (or whatever you like) making sure the corner opposite the gap is about 1-2 inches higher than the other three.
-Put a receptacle of your choice under the notch, put your garden on top, and let gravity do its work to catch all the runoff after watering.
Beautiful. . .now ALL the runoff from ALL the plants is directed into only receptacle, and you don't have to move or disturb any of the plants to empty it, nor do you need any special pump or siphon.
Also, no matter what size pots you use, how many pots, or where you place them, all the runoff will still go to the same place. So if you wanted to add pots later, change their size, or move things around, you don't have to worry about placement or finding other runoff receptacles.
Total cost for this system should be around (if not under) $60, and possibly quite a bit less if you already have access to wood, plastic sheeting, a drain receptacle, etc. If you're a "scrounger" you could probably built it for zero.