So there I was yesterday, looking at my creation. I finally finished my sump, about 25G…bubble tower…3 baffles…refugium… return pump…and an overflow box. I was finally ready to get this up and going. I started the siphon in the overflow box and flipped the switch to the return pump. Water started draining and circulating back up. But oh wait...the return pump seems to be pumping faster then the overflow box is draining. So I pulled the U-tube and unplugged the return pump so I could put together some kind of valve. All of a sudden the water in the sump began to rise. *** is going on I'm thinking to myself. Then the water started coming over the edge of the sump...and coming and coming. About 10G later I realized that the return line had created a back siphon to the sump. Yes, I'm new. Live and learn I guess. Just figured you guys would get a laugh out of this. Anyways I went to makeman today and got some PVC and hard lined the return pump. When it dries I'll give an update...maybe some pics too if I remember.