Should I decrease my return line diameter after a split?!

[trevorspencer94]

Hey everyone,

I am working on ordering the rest of my plumbing for my 40 breeder, and I am planning on having 2 returns, one on either side of a center overflow in tank, from 1 pump. Was planning on using a 3/4 inch return line, and then using a Y or T and decreasing diameter a little bit to maybe 5/8 to help keep water pressure up a little bit to help with flow in tank to prevent dead spots. Would it even work like this? or should I bother? maybe just stay with all 3/4 in line? idk, this is why im asking haha, thanks!

 

[AZDesertRat]

Reducing the diameter increases the velocity but decreases the flow rate. If is turnover through the sump you are looking for, leave the diameter as large as possible. If it is a jetting action, but at a reduced flow due to increased headloss then reduce the diameter or use Loc Line nozzles. I prefer higher flow through the returns then use cheaper powerheads or wavemakers to provide the movement in the display.

 

[mcarroll]

I am not a plumber, but I think the usual reason for reducing after the split is to make it easier to maintain the same pressure at multiple outlets.

With only two outlets I doubt you will run into any issues that would call for reducing pipe size.

Like @AZDesertRat said, you usually want to keep the plumbing large and free-flowing.

There's nothing wrong with getting flow via the return per se (corals won't care!) and you may as well make the most of whatever return flow you are going to have, but...

Flow through plumbing is by far the most expensive way to get flow. Also it can cause side effects with noise and splashing around the drain and sump due to "forcing" too much water through the system. Generally drains and sumps (and the gear in them) run the smoothest at around 2x to 4x the display they were designed to serve.

For example, your 40 would only need between 80 gph and 160 gph through the sump to feed skimmers, heaters and such...your drains whould be silent and there whould be practically zero splashing/bubbling in the sump. That isn't much flow in terms of what your display will ultimately require if you keep coral. Get some quality powerheads like the Tuzne Nanostreams.

If you were running a large retail or breeding system with a few dozen small tanks running off the same pump (not just two outlets), I suspect you'd have a lot more issues balancing the flow to all those tanks without having the right reduction for the outlets.

 

[trevorspencer94]

Thanks for the replies! I just might do that and undersized the return pump so it's extra quiet and just compensate by having power heads inside. Thanks!

 

[Rjramos]

Trevor, that's the great thing about this hobby and these forums. You can get informed before deciding.[emoji4] There has been a new trend over recent years in reef keeping to reduce the turnover rate( water going to your sump and back up) and augment with powerheads and wave makers within the display. I am an old school reefer and a firefighter who has a pretty good knowledge on hydraulics. Most overflows with a 1" bulkhead at the bottom can handle from 600-800 gph. Overflow noise can be reduced with a riser installed. IMHO, this volume should determine what pump you get and how you plumb it going back up. I've ran smaller than 40 gal tanks this way without installing a single powerheads in the display and turning over 10x! It is in the sump where skimming and filtration take place and my reason for high turnover. If you reduce the pump outlet from 1" to 3/4" right away, you can forget about what the pumps capacity (GPH) is, you just significantly reduced it. Most overflows come with a 1"outlet bulkhead and a 3/4" return bulkhead, they reduce the size of the return so that the overflow capacity (gravity) cannot be exceeded by the pumps( pressure) capacity. As far as efficiency and cost, I would suggest you get a pump to meet the turnover rate you want. Don't reduce the 1"diameter of the pump outlet for as high as you can until you have to tee to the 2 returns. Coming out of the tee you can go 3/4" and then place nozzles(loc-tite) to increase pressure inside the display tank. I did not see mentioned but are you going out and back in through your overflow? And if so are those 1" and 3/4" bulkheads?