Secondary Return Pump For Closed Loop

[jadefox]

I want to set up a second return pump from my sump that will be dedicated to my closed system PVC rock rack (the rock rack has holes drilled for current). My main return pump in the sump is 900 gph and is 63 inches beneath the top of the display tank. This pump returns water through the chiller before it goes to the tank. My current overflow box set-up can handle 1000 gph.

Do people have recommendations on a secondary pump?

[motorslave]

Well if you're pumping from the sump it isn't a closed loop. A closed loop has no exposure to air and is a completely closed system. If you were pumping from the tank and back into it that would be a closed loop.
The biggest issue I see is back flow. If you were set up as you describe and the power went out, the tank water would siphon back into the sump, down to the level of the rock rack in the tank. You could use a check valve but they are not recommended in general due to the fact that the saltwater environment has a tendency to render such things useless by the build up of calcium and such.

[Doug1]

Gotta agree with Robert on this one, I would do a second closed loop to accomplish what you want, you could set up an over the top CLS(see Geoffs build thread)

[jadefox]

Originally Posted by motorslave

Well if you're pumping from the sump it isn't a closed loop. A closed loop has no exposure to air and is a completely closed system. If you were pumping from the tank and back into it that would be a closed loop.
The biggest issue I see is back flow. If you were set up as you describe and the power went out, the tank water would siphon back into the sump, down to the level of the rock rack in the tank. You could use a check valve but they are not recommended in general due to the fact that the saltwater environment has a tendency to render such things useless by the build up of calcium and such.

I see. Sorry about the nomenclature problem regarding the closed loop system. I worried about the backflow problem as well, and I had considered a check valave, but I hear you on the issue with check valves and salt water. Someone else had suggested installing an air pipe on the top of the return to break the siphon and halt the back flow in the event of a power outage.

[jadefox]

Originally Posted by Doug1

Gotta agree with Robert on this one, I would do a second closed loop to accomplish what you want, you could set up an over the top CLS(see Geoffs build thread)

I'll check out Geoff's build thread. Thanks!

[jadefox]

I think I'll use this system. Thanks again for the help!

http://www.melevsreef.com/closedloop.html

[jadefox]

Originally Posted by jadefox

I think I'll use this system. Thanks again for the help!

http://www.melevsreef.com/closedloop.html

Okay. So I was thinking of going with the Mag 3 or 5 like the sytem described in the link, but when I went to order it, I saw that it says "Mag-Drive pumps are not recommended for saltwater aquarium external use." Hmmmmmm. Any thoughts? Should I go with a TAAM or Eheim?

[Geoff]

i have used Mags in SW systems externally before. not a problem. the reason they say that is due to Calcium buildup on the impellor. if you keep your Ca levels above 350, then the heat generated around the impellor attracts Ca. eventually the Ca buildup is so much that it can cause the impellor to sieze and burn out the motor. if you keep your
Ca levels under control around 350 this should not be a problem. if you check the impellor a couple of times a year you should also be fine.

G~

[jadefox]

Originally Posted by Geoff

i have used Mags in SW systems externally before. not a problem. the reason they say that is due to Calcium buildup on the impellor. if you keep your Ca levels above 350, then the heat generated around the impellor attracts Ca. eventually the Ca buildup is so much that it can cause the impellor to sieze and burn out the motor. if you keep your
Ca levels under control around 350 this should not be a problem. if you check the impellor a couple of times a year you should also be fine.

G~

Thanks. I'll go with the Mag 5 then. -R

[jadefox]

Here's a question...would there be any advantage or disadvantage of rigging up the chiller to the CLS instead of having it in-line between the sump and the display tank?

[Doug1]

Originally Posted by jadefox

Thanks. I'll go with the Mag 5 then. -R

Typically rock racks drilled like you plan let a lot less water thru them than you might think, Personally I think a Mag 9 or 12 would give you a lot more flow, you want to keep things moving, right?

[jadefox]

Originally Posted by Doug1

Typically rock racks drilled like you plan let a lot less water thru them than you might think, Personally I think a Mag 9 or 12 would give you a lot more flow, you want to keep things moving, right?

I'm looking to upgrade now. Thanks.

[Doug1]

Originally Posted by jadefox

Here's a question...would there be any advantage or disadvantage of rigging up the chiller to the CLS instead of having it in-line between the sump and the display tank?

It will probably work either way and be fine, BUT typically you are going to push a lot more volume through a closed loop than you will through the sump. Slower velocity through the chiller should increase its efficiency I believe, as well as exposing all the water volume to the chiller.

[Fly Guy]

I like plumbing my chillers off of my return pumps. aIt is easy to control the amount of flow you are actually giving the chiller that way, and it is not taking away from the CLS. This is especially important on a cls that is powering spraybars, you want everything you can get to tgo to the spraybars.

You will of course need to have a return pump that has the appropriate amount opf power to power both the chiller, and to roughly match the amount of water that your skimmer can process.

[Doug1]

Fly any idea how much restriction a chiller typically adds to the return system?

One of the reasons closed loops have become popular is that it allows you way more flow rate in the display tank than you can get draining into a sump and pumping it back. Higher sump velocities tend to create more noise and salt creep issues. Slowing the throughput rate in the sump makes these issues easier to deal with and as a bonus the slower the water flows through the more likely the skimmer can process the water draining from the display tank