Should be connected to the resivoir. I don't like those systems because the water sits still most of the time. My system uses 2 resivoirs. A small 16gal resivoir sitting on the ground that all the buckets drain into, and a 55gal resivoir sitting a few feet off the ground that gravity feeds all the buckets. There's a pump like this one
http://www.harborfreight.com/cpi/cta...emnumber=45014 in the small res so when it starts to get full it pumps the water into the big res and just keeps flowing. It makes it much easier to add nutes or change the ph because the water is always circulating through the buckets and it keeps all the buckets at the same ph and ppm.