View Full Version : Closed Loop Manifold vs. 6-way splitter

07/08/2007, 10:06 PM
I love the idea of the closed loop manifold for high flow without all the powerheads in the tank (commonly suggested by Calfo). I do find it to be pretty bulky and cumbersome though, even when using a full canopy. If it's under the lip, then it's too visually distracting.

While browsing the FlexPVC site, I came across their 6-way manifold. 2" in to six 1/2" out pvc fittings - http://www.flexpvc.com/cart/agora.cgi?&product=PVC-Manifolds-Distributors

I was considering getting that for my 75g in the making, and running flex lines to a few acrylic plates with bulkheads, then loc-line, and possibly eductors (if I can design one well enough). Full 2" pipe up until I need to split. 6 outputs from that(CL), and 2 from my sump return.

Seems like a better way of doing it, and possibly a bit less flow restriction, as well as less piping in the way. I suppose you could pop in a few Squids or OMs, etc.. in there as well if you really wanted to.

Anyone see any cons to this?

07/15/2007, 12:16 AM

This is the "6port distributor" 3rd row down.

Was considering also putting 2 of those on a true 2" wye for 12 outputs total. Then run some nice flex pvc to the outputs, all coming from rear of tank.

07/15/2007, 09:20 PM
I use a 1 1/2 to 6 1 inch on my hammerhead works great !made it so i could run 1 1/2 to the op of the tank and then 45 / 90 were i wanted the 1inch runs !

07/16/2007, 12:29 AM
I don't see how you would hook it up so it doesn't look like an octopus in the middle of your tank

07/16/2007, 10:01 PM
It wouldn't be in the tank. It would be in the rear on the pipe coming up from a Dart, then splitting off to outputs in the corners of the tank or so.

Arnett - interesting, haven't seen a 1" output version anywhere yet.

07/17/2007, 04:31 PM
I just helped plumb a new tank in this fashion about 3 weeks ago. We ended up having almost 200 glued joints but it worked out well.

My friend set up a new 120 gallon and wanted 0 powerheads. We set up a closed loop with a Sequence 4300. The suction side is 2" and is over the tank lip (the only holes in the tank are for the overflows and returns). That pipe goes down and 90's over to a side cabinet and 90's inside it to the pump. The output comes out of the cabinet, 90's toward the tank, 2 45's offset to ride against the stand then turn 90 to vertical and hits our DIY manifold. Everything is 2" pipe to here. We cemented 2 4-way 2" crosses together with the shortest piece of pipe possible. That gave us 1 2" input and 5 outputs. Reducer bushings were installed on the crosses to switch to 1" pipe. The top output goes to a sea swirl in the middle of the tank. The 2 next highest outputs (on the sides of the top cross) 90 up from the manifold and feed the middle and bottom of the tank with flow. The low side outputs go toward the sides of the tank until they're to the inside of the overflox boxes then 90 up to the tank rim and 45 to the side wall and 45 to the front corners. After that several threaded 90's provide adjustment to the 2 penductors pointed toward the center of the tank. The system has about a dozen unions to make it easy to dismantle and the 3 non-penductor outlets have valves to control flow.

Hope that gives you some ideas.

The worst part about the process was when we thought we were going to have to buy another 2" true union ball valve. I'd glued a 90 onto both of the ones right at the pump without the locking ring on there around 2:30am. Luckily we were able to remove (dremel and pry out) the pipe and reglue that joint with tons of primer.

Those are my thoughts, measure twice, cut once, sand, prime, cement, and most importantly pay attention to what you're doing. We decided to call it a night after almost ruining a $35 fitting.

Oh, but to address your main question, you can build your own manifold to suit you exactly for $10-15.

And I'd stay away from flexpvc. If you've never handled the material before, it's likely not what you think it is. It's a pain to glue (if any stress is applied to the joint it will leak), doesn't flex much at all, and is expensive. It just seemed to get in our way.

07/19/2007, 11:46 AM
Does anyone know what kind of flow loss/restriciton you are looking at if running a 6 port distributor like that with a Dart?

How about the math to determine the ideal outlet port size?

It seem that 6 x 1/2" is quite a restriction on flow?

07/20/2007, 07:58 AM
It seems like you would have no loss at all in total flow because inlet is 2" and each outlet is 1/2". So 1/2"x6 =3" right? Your outlet is actually bigger than inlet. It seems like the only value lost is going to be in outlet velocity. So flow rate should be the same as that indicated by the pump for current head hieght.

07/20/2007, 01:31 PM
You actually need to compare that with area and not diameter. The comparison would be (2/2)^2*pi > (.5/2)^2 * pi *6. The pi can cancel out and you end up with 1 > .375. Without pi that tells you a 2" pipe has more than twice the cross sectional area of 6 1/2" pipes. It would take 16 1/2" connections to give the same area as 1 2". And you'd still see restriction from increased friction (more pipe wall per area).

Change the outputs to 3/4" and you get 1 * pi > 0.84375 * pi (which is (.75 / 2) ^2). Still the 2" is more area. You really have to use 1" (results 1 * pi < 1.5 * pi) with a 2" input and 6 outputs. This is of course assuming 2" is not oversized for your pump, which it may be slightly. But I think you'll still see quite a bit of restriction with 1/2" outlets.

07/20/2007, 02:02 PM
Thanks Siffy, I knew someone would know the math. So you would need 2" to 6x1" manifold to maintain flow. Something to think about.

07/20/2007, 03:25 PM
Yep, if you use as few as 4 outlets you'll need 1". If you have 7 or more 3/4" will do (that one comes out to 7.1111 3/4" to 1 2"). And again, you'd need 16 1/2" to have the same area.

07/20/2007, 04:00 PM
Is the denominator in paranthesis the diameter of the pipe?

07/20/2007, 06:31 PM
Which set? The only thing I ever divided by was 2. And that was simply to get the radius of the circle from the diameter of the pipe to put that into the equation to get area of a circle, A = pi * r ^ 2 = pi * (d/2) ^ 2. It's always 2 because the radius is always half the diameter, not just in this case because of the 2" pipe.

07/20/2007, 09:59 PM
I was just checking to see how many outlets would be required and of what size if I went with a pump that had a 1.5" return.

07/20/2007, 10:19 PM
I'd probably run an oversized 2" main out of the pump to a 4 outlet 1" manifold (1 cross and 1 tee). Unless you need more outlets of course. Still then (with more outlets) I'd oversize it because larger pipe handles bends better.

07/21/2007, 10:01 PM
The 1.5" to six 1" version Arnett mentioned would seem to be ideal then.

I just did a Google search and found this page http://www.swimmingpoolsetc.com/spa-manifolds-pvc-fittings.htm

Lots of better sized solutions.

Also, thanks for the math. I didn't bother doing that part of the research just yet.

11/27/2007, 02:28 AM
Flexpvc has those fittings too. (and for a lot less money.)


11/27/2007, 08:12 AM
You guys lose me as soon as you start talking all this math nonsense. Make sure you have enough pump to push through all of the outlets or you will be dissapointed. I think the 4 way is the way to go.

11/27/2007, 10:39 AM
Here is an easy way to understand the math part.

Take a piece of paper and draw a circle 2" in diameter. If you have a compass that's even better. Now in that 2" diameter circle, take something like a dime for 1/2" or a penny for 3/4" or quarter for 1" and see how many you can fit in that 2" circle.

Just getting "enough pump" to force the water thru is not the answer. Not only is it noisy and inefficient electrically, but it's a waste of money buying too big a pump than is needed.

(In truth a dime is actually quite a bit bigger than 1/2, but for illustration purposes it suffices.)