If you have a solo channel and need to connect a pump to the channel this is the add on you need. 

Note This is the feeder end of the Solo system.

You add to the first channel,

then use 19mm hose to drain or connect other channels.

So to connect channels, and to have them run back to the tank all you will need the 19mm hose per meter

(to purchase the 19mm drain hose see the link below)