diy pvc overflow length ?

[jhicks]

how far does the pipe need to go into the tank? all the way to the bottom?

 

[FishFlake]

The bigger the distance between the "T" outlet and the surface of the water, the more flow you will get. The deeper in the tank your inlet tube goes the lower the "T" can be (the "T" must remain above the "U" in the tank however).