Hey bds,
Instead of using copper piping and freon to transfer the heat from your air handler in the room to the outside a/c split condensing/compressor unit like in a split system, the water cooled self contained unit uses freon and water in one complete unit. The one unit has a water in (your city water line), water out (this is expelled pressured water from the unit that needs to go into your plumbed drain that is now warm from removing heat), and a water condensate drain out (condensate water comes from the radiator on the a/c and you can drain this into the same drain the pressured water out goes into)
The water out is pressured so you don't have to worry about gravity flowing your water to a drain, but the condensate drain line isn't pressured so you either have to tie it into the pressured drain, or you can have the a/c set up high enough off the ground so the condensate gravity drains itself to your plumbed drain.
Or a third option is to use a condensate pump (about $30-$50 hardware store) to make the condensate drain pressured so it can flow up hill against gravity if needed to drain to your plumbed drain.
You can get these systems from 1/2 ton up to 12 ton and are very simple to install.
You need to put them on their own breaker. A 3 ton should be on a 30 or 40 amp breaker. You can get them either 120 volt or 240 volt. The 240 volt equipment is more efficient for energy usage.
Another cooling option is a unit called a swamp cooler. They come in single fan, double fan, three fan, or 4 fan. They only use air and water to cool, no freon, and don't have the cooling capacity as a true a/c but they are good for shows from 1 to 6 lights. The problem that can arise with them is that they use water to cool with so if your city water gets warmer in the warm summer months then the cooling power of the swamp cooler drops because of the warmer water. For these units to work well your water should be more around 45 to 55 f. Any warmer the cooling capacity of the unit diminishes quickly.
The top picture is a water/freon cooled a/c. that was set up in a sealed 8 light room with co2.
Similar units can be seen here:
The lower picture is a 3 fan swamp cooler that was set up in a sealed 6 light room with co2.
A 4 fan swamp would have been better in that room.