View Full Version : Why isn't my Cube draining fast enough??

12/20/2009, 03:42 PM
I have a Marineland cube, and the bulkhead is on the back pane of glass. There is a PVC elbow which for some damn reason they appear to have glued in place, and I can't remove it from the bulkhead. The elbow is tapped with a small airline hose to add air.

The tank is about 10 feet from the sump, but I have it plumbed with large PVC and the run to the sump is all downhill. I even upgraded PVC size to see if I was bottlenecking it, but it hasn't made a differance. It simply won't drain fast enough and won't draw air through the air hole. I can't figure out why this is happening. Any suggestions very welcome. Thanks.

12/20/2009, 03:45 PM
Throttle down your return pump with a ball valve on the output side.

12/20/2009, 03:46 PM
how much volume are you trying to push through it?

12/20/2009, 04:02 PM
The flow is T'd off my main pump that feeds several tanks. I do have a ball valve on the output, but I can barely put anything through it. I'm not sure why it won't even start a siphon, as I've tried plugging the air end. I have clear 1 1/4 tubing on the drain, and I'd say the tubing is only about 1/4 full.

I have a 70 gallon tech tank that is right next to this tank. It is drained on the bottom of the overflow and I can pump a ton of flow through it. I am boggled.

12/20/2009, 04:14 PM
is the drain under water in the sump or over go horizontal at all on the way down? this drain is tricky, but if you play with it, you can push about 350 gph through it and it'll restart by itself with no problems. It is a bit noisy though...

12/21/2009, 11:25 AM
The drain is not under water. The only horizontal run is the one that is necessary to get over the return bulkhead. Every time I think about how Marinleand made this thing I get angry. If you have a pic of how you plumbed yours I would love to see it.