please explain how a drilled tank works.

[mr funktastic]

ok so i got the gist of it that htere are 2 holes. one for output and one for return and there is some kind of overflow infront of the output. but i just have never seen one so i cant put it all togehter. i was planning on making my own sump and drilling my own tank but i want to fully understand how it works. i want the holes to be at the top of the tank aswell and not the bottom so just incase it ever decides to mess up i only loose some water not all of it. i realise this is a noob question but any kind of link would be appreciated. thanks

[melosu58]

Moving this to Hardware and equipment discussion.