flow for closed loop

[randy123]

Wondering if anyone knows the recommended flow rate for a predominately LPS tank. I'm looking at installing a closed loop, and need to decided which direction to go.

[Reef Pilot]

Why would you go with a closed loop system instead of in-tank powerheads or a WaveMaker?

I have a big honkin MDM pump with a 1/4 hp Baldor motor (thinking of selling it to someone needing a large return pump) that puts out 3600 gph (might be more) through 3 outlets in my 100g display tank, but barely moved stuff in my tank. I replaced it with a Coralife 5800 Wavemaker that produces a way more flow (no comparison, actually), and uses a fraction of the power. And no plumbing to set up. Also, you can adjust the flow to what is best for your corals.

[sphelps]

10X turnover is enough for LPS only. You can do more but going over 20X may actually cause problems but it does really depend on tank size, layout and flow velocity.

[The Grizz]

I have 3600 GPH on my closed loop on the 165gal, 4 returns though an OM 4way.

[randy123]

What types of problems with higher flow might you expect? I am planning on mainly lps, but I would like to leave the door open for a few easier to keep sps if i can.

I was considering a dart pump on an OM 4 way, tank not as big as Grizz's though, its about 130 gallons (5')

[sphelps]

Many LPS do better in lower flow, many if subjected to SPS type flow requirements won't open and expand fully and do poorly as a result. With a closed loop you can point flow upwards towards higher portions of the rock work that could contain SPS and LPS will do well below. Also keep in mind if your pump is rated at 3600 GPH and you run it through an OM and typical tight closed loop plumbing you'll probably see closer to 2000 GPH if that. Closed loops don't have static head but do typically have more restrictive plumbing, especially on the intake which has the greatest effect.

[randy123]

I'm thinking of plumbing with spa flex after the OM, I think the discharge side with be completely free of 90s. I was thinking twin 1 1/2 inch lines going to a 2 inch header for the suction, one I can make straight down to the pump, the other will have a couple bends and a few foot horizontal run.

Do you know how much flow restriction occurs in the OM itself?

I like the idea of some slower spots for the lps at he bottom, as long as the gunk in the water will stay in suspension.

[fencer]

80 % closed loop circ

[sphelps]

For the intake you'll want dual 2" lines, not 1.5" if you're running a dart. Large strainers are key as that can be the biggest problem for restriction.

The amount the OM will restrict your flow will depend on the original flow rate but I find then pretty restrictive overall, I'm considering removing mine for this reason plus the timing motor tends to squeak, the drum jams up sometimes and it's a pain to maintain in tight spaces.

Personally if it were me I'd skip the OM and but two pumps instead. Plumb one pump to pull water from one side of the tank and push water in the other side. Plumb the second pump the same but opposite. Then use couple timers or a single timer and a NC+NO relay to switch between the pumps every hour or so. This way you get true alternate flow, less restriction and redundancy.

[untamed]

Each of my CL Dart pumps pull through a single 2" intake. Suction is not an issue. As said, the key is to have a large surface area strainer.

OM 4 ways work very reliably. I dislike the look of power heads in the tank.

[The Grizz]

The way my CL is done is how it was reccomeded by the owner of Oceans Motions right down to the size of pump, I believe it's all in my build thread. Spent several hrs talking to him on the phone & got some great info.

[whatcaneyedo]

I love my OM 4 Way which is fed from a Reeflo Dart on my 120gal. 2" into the pump, 1-1/2" out into the 4 Way and then four 1" returns. Its been running problem free and dead silent for several years. The back pressure/ head loss of it is no different than that of a T fitting.

I don't like the idea of having large aquarium pumps or even cheep power heads switching on and off constantly. I know Danner Mag Drives handle this poorly as I've wreaked a number of impellers this way. I've wreaked quite a few maxi jet impellers by switching them on and off too. Perhaps the higher quality pumps would handle it better but I'd do some more research.

I've always personally believed that LPS should have no less than 20x turnover. There are at least a dozen different LPS with 30x to 60x turnover around them in my system and they all appear to be doing great. Except for those that were preyed upon by my fish... There are plenty of pictures for proof in my Tank Journal.

Obviously I'm also very pro closed loop. Big ugly power heads stuck to the glass ruin a display in my opinion. Especially when they become plugged up with algae and debris. Yes the electricity consumption of a big pump sucks but I feel that its worth it.

[randy123]

I've heard that the newer OM's have small grooves built into the drums that allow a little bit of water by...they say this helps with the sticking that can result when sand or whatever gets in there. The plan for my setup puts the OM in a fairy accessible place as well, so I'm not too worried about that aspect of it too much. The OM is already ordered a few days ago...I got drum #3 for now.

I'll have to look at your thread later tonight Grizz, sounds interesting. I'm at work on nightshift, so I should have plenty of time to go through it...

While I have the tank down and drained for the install, it might not be a bad idea at all to add the plumbing for a second pump, but I don't think I will buy one for now. My wife has been understanding up to this point, but I don't want to push my luck.

[randy123]

I was think of 4 inch outlets as well, maybe for a back and forth wave effect?

[mark]

I'm another using a Dart with a 4way (single 2" inlet and 4-1" outlets). In the 6 years running had to replace the Dart once but 4way has been going non-stop.

[sphelps]

Dart and similar pumps are no different in design than most hot tub pumps, they will work perfectly fine turning on and off every so often. Would also give the motor a chance to cool. But I digress.

Not sure what your install plans are but if you can put the OM sideways and over the sump it makes maintenance a lot easier and less messy.

http://i84.photobucket.com/albums/k36/EngineeredAquariums/DSC_0010.jpg

http://i84.photobucket.com/albums/k36/EngineeredAquariums/DSC_0024.jpg

[sphelps]

The way my CL is done is how it was reccomeded by the owner of Oceans Motions right down to the size of pump, I believe it's all in my build thread. Spent several hrs talking to him on the phone & got some great info.

This one?

http://i765.photobucket.com/albums/xx291/GRIZZtheWELDER/165%20gal%20tank%20build/100_3237.jpg

[The Grizz]

Yep that one :lol:

And this one that shows the intake manifold but what I didn't get a pic of is the loc-lines that are attached to the returns. I put 3 - 3/4" on each return.

http://i765.photobucket.com/albums/xx291/GRIZZtheWELDER/165%20gal%20tank%20build/100_3235.jpg

[sphelps]

So what size lines are those and what size pump exactly?

[The Grizz]

So what size lines are those and what size pump exactly?

Intake is a 2" line & returns are 1" so when running its a even ratio of 2 - 2. The pump is a Dolphin 3600 GPH. Loc-lines calculate out at 2 1/4" per return.

[sphelps]

Intake is a 2" line & returns are 1" so when running its a even ratio of 2 - 2. The pump is a Dolphin 3600 GPH.

Thanks, what do you mean ratio of 2-2?

[The Grizz]

Thanks, what do you mean ratio of 2-2?

2" intake / 2 - 1" returns

[sphelps]

Oh OK so actually you have a 2-1 ratio relating to area (2^2 : 2x1^2)

[The Grizz]

Actually now that I think of it, it's really a 1-1 ratio related to water volume in & out. I might be totally off here because of an 19 hr day yesterday.

[randy123]

Yeah, the OM will be over the sump, kind of like that

[randy123]

Grizz, what was the reasoning behind leaving the closed loop down for the first bit after starting up your tank?

[FragIt Dan]

Actually now that I think of it, it's really a 1-1 ratio related to water volume in & out. I might be totally off here because of an 19 hr day yesterday.

Flow is relative to cross sectional area, so for 2" pipe it is 3.14x1^2= 3.14 vs 1" at 3.14x0.5^2=0.79, but two of them so 1.58. That puts it at 2:1. You would need four 1" return lines to prevent a bottle neck.

[sphelps]

Flow is relative to cross sectional area, so for 2" pipe it is 3.14x1^2= 3.14 vs 1" at 3.14x0.5^2=0.79, but two of them so 1.58. That puts it at 2:1. You would need four 1" return lines to prevent a bottle neck.

Velocity is relative to cross sectional area, in theory flow is the same no matter what but friction losses are greater with higher velocities but there are limits or critical velocities, eg pushing 200GPH though a 6" pipe won't make much difference over a 1/2" pipe. You can also drop the pi/4 when comparing ratios as it's a constant (just square diameters).

Also consider the pump Grizz uses is 1.5" in and out, the intake is one size up which is a good idea considering it's pretty restrictive. The output stays at 1.5" and then splits into two 1" lines at the OM, so at the output side it's pretty much 1-1. So to say there is a bottle neck isn't really correct, if that were true any pump that had a larger suction would have such design flaw.

That said it's still pretty restrictive plumbing which, like I said earlier, is typical with closed loops, especially with smaller tanks also containing a sump below. To say 3600GPH is going through it isn't very accurate, in the mid 2000s is probably more accurate. That combined with the return and flow probably sits pretty close to 20X. Would his LPS suffer if he dropped his turnover to 10X? Not likely.

[The Grizz]

Grizz, what was the reasoning behind leaving the closed loop down for the first bit after starting up your tank?

It was blowing my sand all over the place because I didnt have my Loc-line in yet and it gave the sand time to settle a bit.

[randy123]

Oh, Okay. Makes sense.

Well I think I've got it figured out...everything is ordered up. Thanks for the advice everyone.