Oversizing Drain?


Junior Poster
Apr 16, 2009
I recently acquired a 155 bowfront that was used as a reef tank. I’ve been reworking different parts of the setup to suit a planted tank. One of the first things I did was build a pair of stockman standpipes due to the Niagra falls sound coming from the 24” long center overflows. The back wall of the tank is drilled with 2 1” bulkhead for the drains. Those standpipes alone made a huge difference in sound.

Then I moved on to reworking the sump. The sump is a 40g long (48” I think). Originally the sump was divided into 2 chambers. The left side was setup as a refugium and the right side had the main drain, filter sock, heaters and bulkhead for the return pump. That setup made no sense in my eyes for my needs so I removed the center partition, and rerouted drains (inlet to sump) to the far left side of the sump. There is about a 24” run of 1” pvc that is almost horizontal. After rerouting the sump inlets my pump is now more powerful than the drains. So basically I’ve created too much backpressure on the sump inlet with the nearly horizontal run, and 4 90* fittings as well. One thing to note is that there has always been the 4 90* fittings.

My question is whether or not I should change out the 2 90*’s and the nearly horizontal run with larger(1.25’ or 1.5”) pipe to reduce backpressure and allow my drain to function correctly. Honestly I’m not even sure if that will resolve the problem but I’m hoping it might.

I’ve been able to manipulate the stockman standpipe to keep the water level stable but it seems that I’m right on the brink of disaster.


Plant Guru Team
Lifetime Member
Sep 23, 2007
South Florida
I will reply with more detail later, but install a ball/throttle valve on the outlet of the pump and reduce the flow until the level is balanced.

Going to a larger size drain will only make the pump work better, so the ball valve will really be required at that time.

A larger diameter pipe flow more water but at less velocity.

Hope this helps.