Double Pumps?

[hyperfocal]

Is plumbing two pumps together on the return a bad idea? Something like:

 

[Wryknow]

You'll get a lot of back-pressure where the two water jets meet. Plus, if one of the pumps goes out (or is much smaller than the other) the water will just flow through the pump that is shut-off instead of being returned to your tank.

I would strongly recommend having completely separate return lines on each pump. Run one over the top of the tank with a u-tube if you don't have holes pre-drilled in your tank for the extra return line.