Drain placement - Back of tank or Bottom?

[NewKid630]

Is there a performance difference between a drain being in the bottom of an overflow box or in the back of the same box?

My problem is the bottom of my new tank is 18" from the floor, and the sump is 24" tall in the next room. I can either use the standard 2 x 1.5" drains and let them go up 6" before draining or put the bulkhead in the back of the overflow and have it all drain down hill.

Im trying to not lose any performance with the drains.

Reason I ask is I have a 40 gallon tank with the drain in the back towards the top and it doesn't drain nearly as quick as another 40 with the drain on the bottom and both have 1" pipe.

 

[Blown 346]

I owuld do the drain on the bottom with a 90 degree albow, and run the pipe down to the filter.

 

[NewKid630]

Even though the filter will be 6" higher than the drain?

So it will look like this:

Tank Sump
/-----\
L____________/

 

[Shaun120]

Though it may be slightly elevated from the drain you will still probably get the same performance from the two options your looking at. The pressure created by having a higher pressure gradient in the tank may increase due the slightly higher head pressure resulting from the slight elevation of the sump will cause the water to flow faster. In my opinion the performance of the drain is more driven by the diamater of the fittings and pipes/tubing involved than the location of the drain.

IMO, I have had both types and was able to use the same pump and the flow seemed the same to me (same size tank). Someone will jump on here and call me crazy since I did not get a flow meter on it to verify my observation, but I think the difference will be minimal.