Thanks Melev! - Built a HOB closed loop

[stugray]

Thanks to Melev ( http://www.melevsreef.com/how_to_build.html )

I was able to build this simple HOB closed loop for my 75 Gal that was lacking in the flow dept.

Here's a pic of it being tested while hanging on the front of the tank, prior to installation .. on the back.. .

This gives some really good chaotic flow to the tank. I tested it with bubbles, and it looks as good as Melev's demonstration.

It has the basic siphon tube ( with fill plug ), SQWD and dual nozzles for returns. Mag 9.5 should give me the full 950 GPH ( minus friction loss only ) since it is effectively zero head pressure.

Stu

 

[loudog]

I have the same set up on my 75. Its been up and running for about 6 mounth with no problems (knock on wood). Its probley about time to clean the pump.

Lewis

 

[goavs21]

Not to be negative to your setup, as I think more flow is good, and I'm sure you (& your corals) will like the extra movement....

I do not think you are seeing zero head loss. Looks like you are pushing that back up ~ 4', plus the 90s, and I think you'll find the SCWD will take somewhere in the neighborhood of 20% too.

Joe

 

[stugray]

goavs21,

Thanks for the input.

Since I am pulling water from the same level that I am pumping it to, there is a headloss of zero ( diff between in & out potential energy ). I admit that I will have a lot of resistive loss ( due to the valves, tees, & elbows ), but it is a LOT less than if I were pumping from the sump Up to the tank.

 

[vypr2002]

actually the scwd can take as much as 30-40 % of your pump.
those things eat up flow big time.
its best to increase tube diam, so as to minimize loss

 

[killercoral]

Stugray, I was also a little confused about your 0 head statement. I am by no means an engineer and I am sure that you are correct as I see that you are one. Can you please explain the concept. I assume that it has something to do with the fact of the weight of the water from above cancels out the weight of the head pressure. Is this about right?

 

[vypr2002]

as a genral rule each 90 bend is equivalent to 1foot pf HP
plus you have to take frictional loss of the pvc.
I dont quite understand how you are not pumping from sump level.
you pump is right near your sump level in the pic.you still have to fight gravity to get back to the tank outlets.
btw I did the same thing you did, I ended up with 3 manifolds for a 4x2 tank top before I settled on the one that gave me the best flow.
just my 2 pennies.

 

[prsguy]

I'll wager 1 donut that there is in fact head loss.


F = G M1M2/d2

where F is the force between the bodies of masses M1, M2 and d is the distance between them. G is the universal gravitational constant.

 

[stugray]

To all above:

I am siphoning from the top of my main tank.

I am pumping back to the same level ( top of main tank ).

Once I prime the siphon, the input water level & the output water level are the same.

prsguy, I dont think your equation above applies to this problem.
( it looks more like the gravitational attraction between two bodies .... )

I may have misstated slightly, the elevation head loss is zero ( that is the 'head' that you must pump to get uphill ). In the pump ratings, the 'Max Head' is the maximum that the pump can pump uphill, and also the derating factor of the overall max pumping capacity which is reduced the more lift the pump needs to produce.

The total 'head loss' as defined by fluid dynamics includes frictional losses & dynamic losses.

Anyway, what I meant was that the closed loop runs at the full capacity of the pump ( minus frictional ), and is not reduced by the fact that the pump sits 3-4 feet below the surface.

Stu

 

[FishnWishn]

Actually on the SCWD you can get up to a 40% loss in flow but only if you have a low flow pump. With your pump being rated at 950 gph you should not get more than a 10% loss of flow even with a 4ft head loss. the max pressure a SCWD can take is 1400gph. as you get closer to that # you get less loss due to the faster switching of directions.
http://www.3iqventures.com/literature.html

 

[prsguy]

Indeed it is. I'm not sure I agree (yet still pondering) but since I haven't had physics in 15 years and have many things crammed in my head, most of which isn't fluid dynamics- I'll buy the donut.

If your return was 100 feet above the pump and your overflow was too you are saying there would be 0 head loss? This is because the downward pressure on the water leaving the tank would be nearly equal to the force required to drive water back up to the tank? Am I close?

Glazed or with sprinkles?

 

[stugray]

prsguy,

Think of how a water level works... It doesnt matter if you are working up 3 stories, or one foot. If the water level is full ( even if the bulk of it it is laying on the ground many feet below ), then both ends will have the same level.

Sprinkles...

 

[prsguy]

Yeah, after I brewed up another cup of the nectar (coffee) it started to clear up. I'm cramming for the CFA Level 3 exam so my life is revolving around derivatives right now. It would have been too easy to use the same logic used by the Egyptians centuries ago with little to no education so I thought I'd try to overthink the issue. Mission accomplished.

Melev's site is insanely helpful, glad it worked for you.

 

[dajum]

Stu,

maybe you could settle the loss issue. Try pumping back to a bucket and time how long it takes to fill. Then let us know the flow rate ( or out of a bucket!). I'm betting on only 450-500 gph
after all is said and done.

Dave

 

[artful-dodger]

Stu is right about the head loss (none...just like when you siphon until the two containers are at the same level) and everyone else is right about the friction loss from plumbing (including the special case of the SCWD). Everybody wins a prize!

The bottom line is that his tank has additional flow that it didn't have before. Even if he loses ~450 gph flow, he has still added ~450 gph flow that he didn't have before!

 

[Generic]

Looks a lot like my 2 closed loops

What size pipe did you use Stu? We have 1/2" on the 75G and the friction loss huge! We have a Mag 18 on with the SCWD and we still don't get a lot of flow. I'm going to rebuild it with 1" when we move and the tank gets torn down so I can use a smaller pump.

My 40G has a Mag 12 with dual 3/4" intakes to 1" pipe, then 1" pipe to the SCWD to dual 3/4" bulkheads and finally down to dual 1/2" 45 outlets on each side. It flows much better than the one on the 75 simply because the pipe is so much larger.

Here's a pic of the 40G:
http://www.activeoptics.net/Reef/TankBuild/slides/IMG_4228.html

Murdock

 

[Texas Dolly]

In the instructions for the mag you will see it states "1.5 INSIDE DIAMETER is the minimum hose size that should be used for maximum flow" It looks like you are smaller than that... If so you are losing a lot of flow because the pump is not pressure rated.

 

[s0|]

since my plans also have CL with a SWCD... would you mind
takeing some bigger pics and use photodump.org /rmrc? to host em...
(or if you have the pics alreasy just us use a host that will allow bigger pics.)

 

[dsandfort]

Hi Stu-

Nice job on the CL. Any additional flow will certainally help the tank.

I agree with everything everyone has said. A pump makes no distinction on resistance. Head loss is head loss regardless of whether it is the frictional or gravitational component. Luckily, a CL eliminates head loss due to gravity since the pump does not have to "lift" water. Well, actually it does but the head loss due to the lift is cancelled by the pressure gain from the downforce provided by the suction tube. Total head loss is the sum of all forces resisting water flow. A CL only eliminates the loss due to lift, as you stated.

Bigger pipes most definitely reduce head loss. They also reduce velocity (which is a primary reason there is less head loss) with a net gain in volume due to less resistance. The SCWD is a "choke" point and really does reduce flow. How much, I'm not sure but I think 30-40% is not unreasonable.

Looking at your photo, you might want to try spa-flex from the SCWD on up. That would reduce a couple of 90 bends which, as stated, add more loss.

Lookin good to me.

Del

 

[FishnWishn]

Well I'll be, Mr. Poker himself, Texas Dolly. Welcome to the Colorado Rocky Mountain Reef Club. It was a pleasure to watch you in last years Championships. I was that head bobbing up and down in that wave of onlookers.

Back on topic
Stu, I am planning on using 2 SCWD's on my CL. I am using a 1505 GPH quiet one 6000 for a pump. When I split off the tee to the SCWD's from my pump outlet, would there be 1500 gph going to each SCWD or split 750GPH? I was thinking it would be split to 750 gph each, but listening to your explanation it would seem that flow would be constant until it hit resistance/friction which would be the SCWD's. That would mean that I have 1500 gph at the input to both SCWD's. If that is the case will I have 1500 gph- performance % loss through each SCWD?