Closed Loop Flow

[TitansFan]

Coming down to the end for equipment for my new 65 gallon. All I have left is to figure out the flow inside the tank. Anyone have any experience with sea swirls or squirts? I am leaning towards doing one swirl at one end of the tank with a spray bar for the rocks. Then a seio at the other end. Tank is 36 inches long. Are the swirls worth it?

 

[fishdoc11]

Never used a swirl but I am probably going to buy a couple to use in a couple of different applications. I have heard lots of good things about the flow movement they provide but not so much about their dependability so you might want to get a new one. If it does go out it will get rebuilt for free. From what I have heard/read spraybars really diffuse flow and need a large pump to provide any sort of meaningfull flow in a reef tank. I've never used one of those either though so take that with a grain of salt.

FWIW, Chris

 

[TitansFan]

Thanks for the reply Chris. After seeing so many as of late for sale used it made me start to wonder about the swirls. Even bought new they only have a one year warranty. The problem I am running into now is I started to add up the cost of 2 swirls and the required 1100 GPH external pump. I know I should quit adding up costs but.... It makes me wonder if this is the most cost effiecent plan. The 2 3/4 swirls and quality pump strong enough for them would be around *** (this has been edited for your protection from the prying eyes of wives). I could get a Tunze stream and controller for this price. OOOOO the decisions.. I wish marine depot had an order here now button for closed loops (everything included). Anyone with some other recommendations I could look into would be great!

 

[boofer]

I have a 4-way Om unit and a Dart on a CL. It puts out some massive random flow in my tank. But, thats not a cheap choice by any means...not much worth it is though There are cheaper versions of the OM sized for your tank like the squirt, Super Squirt, you can check out at www.oceansmotions.com Good luck with your decision.

 

[imsqueak]

Hey Titan, check etrc thread for SS and pumps! Charles' equipment
I bought a 1" SS and have been using it with a T4 pump. Not enough flow to make much of the desired random flow effect in my tank with 4 penductors.

 

[TitansFan]

Thanks for the info guys!
I think I shall try to do 2 1/2 swirls on a closed loop. "Ideally a pump with a total of 1100 gph at the head height you are pumping up to" this is what it says on the faq info from www.sea-swirl.com . My question in picking out a pump for this closed loop... Some things I read about head pressure defines it as the pumping force needed to overcome gravity pulling the water back into the sump as it has a way to flow out of the pipe into the sump. Using a closed loop where the water stays in the pump and is just "pushed in a circle" does head pressure really come into play? Will a pump rated for 1100gph at 0 head still do this amount at 4 feet of head on a closed loop?
Second question... The closed loop will be plumbed over the back and top of the tank. For my intake inside the tank can I use a piece of pvc with holes drilled in it?

 

[fishdoc11]

I've wondered about your first question for a long time. Maybe one of the engineers can answer it for us. According to my physics class yes but it seems different in practical application to me.

For the second question yes, just be sure to put a T with a screw off cap in it to prime the pump. This should help:
http://www.melevsreef.com/closedloop.html

Chris

 

[rcmike]

If it is on a closed loop then it would be the same as no head. That is not taking into consideration the friction of the pipe though.

 

[picture the reef]

<a href=showthread.php?s=&postid=6899673#post6899673 target=_blank>Originally posted</a> by boofer
I have a 4-way Om unit and a Dart on a CL. It puts out some massive random flow in my tank. But, thats not a cheap choice by any means...not much worth it is though There are cheaper versions of the OM sized for your tank like the squirt, Super Squirt, you can check out at www.oceansmotions.com Good luck with your decision.

I also have a OM 4 way with Dart on a CL. Provides lots of random flow. Not the cheapest option but in my opinion one of the best.

 

[waldomas]

I just plumbed a CL 1" SS with a corolife turbo sea 1270. Love the flow! I placed it between my overflows on the back and it alternates clockwise / counterclockwise flow around my tank. Its fun to watch all the zenia change direction.

 

[TitansFan]

Yes the OM 4 way looks like the way togo but soooo much plumbing to do. I am just not sold on the over the top 4way. I am abit hesitant to drill that many bulkheads into glass and again sooo much plumbing togo over the tank. The next tank I am really considering acryllic so I can do an OM with bulkheads.

fishdoc11: I am convinced as rcmike says the only thing is the friction loss. Gravity would not come into play because the water in a CL has to "hold itself up" I would like to know how much loss this friction would cause.

picture the reef: do you have a picture of this plumbing?

waldomas: what are the dimminsions of your tank? Is your 1" SS your only flow besides your return?

 

[boofer]

I finally posted some of my progress with my new tank...theres some pics of the OM/Dart CL plumbing in the post. Dustins Cube

 

[Mdwannabe]

Not sure I agree with rcmike, while the basic physics of "work" state pushing is more efficient than pulling, with a pump it's efficient work is done on the positive side (pushing water) not the inlet side (sucking water) this side is less efficient. Moving water up 4 feet (against gravity) regardless of it's direct connection with the inlet (downstream), will reduce the pumps outflow (nothing is 100% efficient), then you can add in the friction (though that is infinitesimal), for yet less flow.
At the size pump you are talking a 4 foot lift (with a closed system) will not affect it's overall flow all that much, as compared to an open system where water has to depend on gravity for it's way back to the pump inlet.
When lifting (any height) against gravity, you can never reach a 0 head flow, direct connect or not (water has weight, and that weight must be moved), at least that's what I remember from my hydraulics classes. Before discovering I liked cutting people open I was a BSME. JMTCW

Rick

 

[gflat65]

Rick,

You did somethign evil with that reply. You prompted me to open my Fluid Mechanics book again after years of it being retired... I read just a enough to be dangerous.

What you said is essentially true. For an abrupt pipe opening (which is what we usually have), there is a noticeable headloss due top separation. On an abrupt pipe inlet (squared with wall of the vessel), eddy currents develop just inside the fitting, which create more headloss. In a rounded pipe inlet (looking at a cross sectino of the wall being penetrated, the inlet has a radius that leads into the pipe, rather than abrupt ends like PVC), there is no separation (depending on pipe diameter and flow), so the head loss is much lower. One inside the pipe, headloss is added by the walls of the pipe (dependant on the coefficient of friction for the given medium). This can be overcome by using a larger diameter pipe to feed the CL pump (drill a 1 1/2" hole and cone down to a 1" for a 1" inlet on the pump, without abrupt edges like bushings). The eddies may still occur, but since the diameter is larger than the diameter that is needed at the pump, it does not create as much headloss. It would take some careful planning to reduce the headloss to near zero at the pump inlet, but it can be done. The friction of the pipe and the fittings create the bulk of the headloss on the return trip to the tank. By using larger diamter piping than the pump is designed for, you can reduce headloss because of this in most cases.

 

[gflat65]

It's all about the eddies that cause constriction (well, almost). Reduce the effect of the eddies and you can reduce headloss. The flow in the middle of the pipe is always faster than the flow at the walls of the pipe due to friction, so larger can be helpful to a point. I'll stop now. My head is spinning...

 

[rcmike]

Okay, think of it this way. If you have the same amount of pipe and same fittings and the pump is on the floor it is essentially the same as if you have it beside the tank.

 

[boofer]

Basically, with a CL the only "lift" youd have is the difference in height from where your intake is to your returns. Other than friction loss, thats your only head because its basically acting as a recirculating pump. Its not the same as if it was pushing water up from the sump against gravity. The only gravity its fighting is the difference between the intake and return holes/fittings. If the intake and return are at the same height its fighting nothing but friction loss. If theres a foot between the intake and returns its fighting a foot of head + the friction loss.
Also, The way to make a pump more efficient on the suction side is to bushing up the intake on the pump. Most pumps Ive worked with in pools require that to get even close to what the pumps actually rated at. A 1.5" intake would be bushing'd up to a 3" in certain applications. Yeah thats extreme for our situations, but going from a 1.5" to a 2" intake would create noticibly more flow for example.