1 or 2 return lines

[melanarus]

I’m getting ready to drill a tank for the first time and am trying to plan out the return line(s). It’s a 120g (4x2x2) tank and I’ve got a 1200gph rated overflow box that I’m drilling for.

Is there a big advantage to drilling two return lines (3/4” ID) or should I keep it simpler and drill one (3/4” ID)? I only use 1 return pump on a basement sump setup.

Has anyone had any regrets on only doing 1 or overdoing it with 2? I’ve only had 75g tanks and smaller in the past and have only done 1 over the top return previously.

Thanks for the input!

 

[theatrus]

One thing I've done over time is to run as slow of a return line as reasonable. 3/4" for 120g doesn't seem at all under-doing it.

 

[melanarus]

Ended up putting in 2 lines of 1/2” each. Seems to be working well.

 

[mikebusc]

Question for you about this since I’m in the same situation as you were. What was your deciding factor in going with two 1/2” returns rather than one? I’m trying to decide the same thing (tank not drilled yet) and if I would regret going with one.

 

[melanarus]

-More balanced look (symmetrical)
-Better reach to detritus dead spots on the back wall when you angle to nozzle down on the back wall

My overflow box went in the middle back of the tank.

 

[Indymann99]

-More balanced look (symmetrical)
-Better reach to detritus dead spots on the back wall when you angle to nozzle down on the back wall

My overflow box went in the middle back of the tank.

Depending on how far below the waterline you “angled the returns down” you are going to want to make sure your sump can handle the back siphon.

 

[melanarus]

Yes, definitely. I have a large Rubbermaid basement sump so not an issue for me.

 

[tzabor10]

Two for a 120 seems right. If one gets plugged up or if a return pump needs maintenance, you have the other. It is also popular to put a UV sterilizer on one return.

 

[mikebusc]

OK so if I use two returns is it a good idea to use two return pumps as well? Or just tee off the one? I know some people have two return pumps but I'm not exactly sure of the reasoning behind it.

 

[dwest]

OK so if I use two returns is it a good idea to use two return pumps as well? Or just tee off the one? I know some people have two return pumps but I'm not exactly sure of the reasoning behind it.

I use 2 pumps on separate lines strictly for redundancy when I travel. Not necessary for sure but I plan to always use both.

 

[Armt350]

I drilled 3 bulkhead holes in mine, 1x 35mm(25mm ID) for water pumped from the sump , 2x 55mm (40mm ID) . 1x is the main drain to the sump, 1 is an emergency drain in case the sump drain clogs. The sump drain flow is controlled by ball valve.

 

[SomeHappyFish]

I did 2 3/3" to get flow on both side.

It help create a bit more random flow and break the watersurface imo.