Closed loop system questions

[richtpe]

I'm planning on building a closed loop system for my 55 gallon and have a few plumbing/flow rate questions. I plan on building something very simlar to the one on melev's reef. I'd like a turnover rate in the tank of about 15 - 20x per hour. The return is going to be about a 4 foot head, so I'm planning to get a mag 9.5, which supposedly will give me a flow rate of 800gph (without considering flow restrictions from the scwd and plumbing) Other circulation in the tank is provided by a maxi-jet 1200 on a remora skimmer, a maxi-jet 400 on a phosban reactor, and whatever kind of pump it is on an emprorer bio-wheel. I want to position 4 loc-line hoses coming into the tank as returns.

What I was planning was to have 3/4" pipe from the mag output go into a scwd, 3/4" hose coming out of each output on the scwd which would connect to a 3/4" loc-line, connected to a 3/4" to 1/2" y-valve, and then have 1/2" loc-line into the tank (total of 4 1/2" loc-line hoses - 2 from each scwd output).

Some threads I've read here and melev's reef site have made me question this plan because of flow restriction. For instance, melev's site states to double the mag's output size on the plumbing to maintain flow rate (which would mean I would need a 1 1/2" pipe out of the mag output). Also, I've read about scwd's cutting down the flow rate (Dave, I'm looking at you).

Which brings me to my long-winded question. Would I be better off designing it with a 1 1/2" pipe off the mag output, splitting that with a 3/4" Y-junction, having that feed 2 scwd's (one off each 3/4" feed from the Y-junction), and then have 3/4" loc-line from each scwd output going into the tank?

Also, regarding loc-line (which I have absolutely no experience with), does it matter what type of nozzle you put on the end? I saw the question raised, but not answered on this thread which made me wonder. I was probably going to go with just a flare nozzle, but if that's not recommended for some reason I'd appreciate any suggestions.

Thanks in advance for any help.

 

[mogurnda]

Welcome to the world of closed loops. Here's an opinion, based mostly on trial and error, rather than science.

Because of the restrictions from the SCWD and the plumbing downstream from it, I would think going with 1.5" pipe on the output of the mag would be pointless. I think 3/4" would be fine, or maybe 1", because that won't be the limiting factor.

On the other hand, you haven't mentioned the input. It may not be a problem with that much of a load on the output, but you can get cavitation if the input is restricted too much compared to the output. That would be where I might think about 1.5" pipe.

As far as the nozzles, it's really a matter of how you want to direct the flow. On my return, I actually use one flair and one regular, because I want different patterns in the two directions.

Real flow-geeks may totally disagree with me, but that's the way it looks to me.

 

[richtpe]

Welcome to the world of closed loops.

Thanks, it's nice to finally be doing this. Me and powerheads with their little suction cups...we don't get along.

On the other hand, you haven't mentioned the input. It may not be a problem with that much of a load on the output, but you can get cavitation if the input is restricted too much compared to the output. That would be where I might think about 1.5" pipe.

That's a very interesting point, especially because for some reason I was going to go with 3/4" without even questioning it (or thinking about it). Thanks for the heads-up there.

Because of the restrictions from the SCWD and the plumbing downstream from it, I would think going with 1.5" pipe on the output of the mag would be pointless.

I'm still a little confused with the outflow and whether it's the scwd that slows it down the most. (Actually, I'm also having a tough time understanding how a pump with a 3/4" output can pump more water than a 3/4" pipe can handle, but I'm just accepting that one). I've come up with two designs below (borrowed heavily from elsewhere)...

So I'm thinking that if the mag's create this super flow and scwd's cut it down, 2 scwd's would be better than 1 scwd and 1.5" pipe on the mag outflow would be da bomb. I certainly think it looks more impressive on paper. But I'm really going for efficiency here and not shock-and-awe, so if it wouldn't increase flow measurably, I wouldn't do it.

So I guess my question now would be if you were doing this, would you go with 1 scwd or 2 scwd, and if 2 scwd what size pipe on the output?

 

[mogurnda]

Me and powerheads with their little suction cups...we don't get along.

I hate them. Nothing in any of my tanks is mounted with them, because I am tired of stuff falling.

I wish I knew numbers for the head pressure equivalent of a scwd, but I don't. I hear rumors of 20% losses, but haven't seen credible tests.

I would be inclined to a single scwd for several reasons. First, it's just simpler. Second, cutting the input to the scwd in half reduces the switching speed. May or may not be an issue. Third, and something that may be more important is there will be less flow to drive the units, and they will probably have more tendency to stop working when they get crusty.

Speaking of which, have you considered OceansMotions units? They don't seize, you have more patterns to choose from, and they don't cut the flow as much. Naturally, they cost a lot more too. A supersquirt is about 4-5X the cost of a scwd.

Honestly, though, there would be nothing wrong with simply cloning melev's system. He knows what he's doing, and nothing will be harmed if you use the larger pipe on the output. I did notice that he suspected cavitation in his setup, though.

 

[richtpe]

Thanks very much for the feedback. I think I'm going to go with the one scwd route. I did check out the OceanMotions site and I think I'm going to pass on those for now. Little too expensive and to be honest, a little intimidating looking for me at the moment (have I mentioned that I've never done anything like this before and have only very, very basic experience working with PVC). I'll try and post a pic of the completed project, if it gets completed without me destorying everything.

Thanks again for the help.

 

[mogurnda]

Good luck. Keep the questions coming!

One more comment. You might consider a ball valve above the coupling on the output side of the pump. It will reduce the mess when you disconnect.

 

[wastememphis]

I don't know if you mentioned it, but you might want to check that its alright to run a mag 9.5 external. You could get a gen-x pump with more power/less watts/less price probably.

(I also don't see the point in using a large pipe comming off the return of the pump, you're probably loosing flow by doing that...)

 

[mogurnda]

Definitely OK to run a mag 9.5 external.

 

[richtpe]

Thanks. I'll probably stick with the mag 9.5 and will probably have maybe 1" pipe max coming out of the outflow (still might go with 3/4"). I've been practicing my "I'm completely lost" look all day and plan to go to Home Depot tonight to spend a few hours in the PVC section trying to figure out what everything is and hopefully leave (eventually) with all the plumbing I need. Tomorrow order the pump and whatever plumbing I can't find at Home Depot, so hopefully I'll be putting it all together next weekend (I'll also need to hit the liquor store at some point before that too, I'm sure).

 

[mogurnda]

I'll also need to hit the liquor store at some point before that too, I'm sure

You may be able to skip this step if you just leave the windows closed when you're using the PVC cement.

One thing that has improved my life considerably is a ratcheting PVC cutter. Looks like pruning shears. Saves a lot of time and makes clean cuts.