It's my opinion that if you're going to do flood n drain the best option is to use 6"x6" or 4"x4" rockwool blocks and use sea of green technique and lollipop all the plants. I don't even use reservoirs, I water all plants by hand...sometimes I top feed and sometimes I just use a 5 gallon bucket(drawing water from a 40 gallon trash can) and fill the tray with water and let it drain to waste. Other growers and myself have hit 1 gram per watt using this technique, I've seen 12 Lbs on 6 lights, 8 LBs on 4 lights, 3 LBs on 2 lights with this method.
If you're only using 1 light then you should only be watering once every other day(assuming you're pulling heat from the light and venting it out of the room).