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Another DIY Skimmer Thread Question

4375 Views 60 Replies 5 Participants Last post by  OneDummHikk
I've been looking though the threads, and am really turned on by this recirculating skimmer:

I've seen the basic design several times, so I am assuming that this works pretty well. I want to know if my feeding/pump would work, or should I use something different. The tank I have is not drilled, so I have a HOB overflow rated at 300gph that I would use to feed the skimmer. The pump that I already have is a Resun 225NW from my Octo HOB. I would meshmod the pump for finer bubbles, but has been a good pump so far. I'm planning on this being an external skimmer with the effluent draining into a sump so that all my overflow water gets skimmed. I currently have a 55, but will have to wait on my large upgrade to the 125 in favor of a 75 with the 55 as the sump. Will this work??? Will this work well??? More flow from my overflow, or bigger pump needed? It seems like I should be close according to info from here.
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Ok I read most of this and one thing that caught my eye was that someone said head presure is not a facter on a recirculation pump.

I may be wrong but I believe it is. Not with GPH of water but with LPH of air. While the head is about the same on both ends of the water intake that is not the case with the air intake. The pump still has to pull air though the entire head of the skimmer.
Here is a simple test. Its not completly acurate because a vacuum is a weeker force than presure. But is you take a piece of half inch tube and b low in it while it is not submersed it is very easy. Take that same hose and put it at the bottom of a bucket and you can feel the presure.

Really it didn't dawn on me at first either but I called sequence to ask them about my orca pump and they said unless you do the alita40 mode to it you can't really run it effectivly over 4 feet of head and I said but its a recirce pump and they said it wasn't a mater of the water flow it was over coming the preasure of the water for airflow. And it then suddenly dawned on me. Go to the sequence website and they have a air flow chart on there for head preasures. I think it also matters on beckette style injectors as well.
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If I had a way to measure the air I would do a test with my skimmer. All I would have to do is put the other 2 foot tube on the skimmer and measure the differance. I'm sure there would be a differance. One of the laws of physics is that nothing can be lost or gained... Ever, only rearanged. My thinking on this is that if you removed the feed pump from the skimmer and had no flow through the skimmer and you turned on the recirculating pump with a 24inch tall body you would have X percent efficiency. If you add another 24inches of body to it you would have X+ percent efficiency. You would have a gain in efficiency but when you have a gain you have to have a loss somewhere. Since we know its not going to be the water flow through the recirc pump the only other variable would be the air intake. I know its not perfect but I don't have any degrees.

How ever I do know this... Its not nessessarily the speed of the air over the wing that causes lift, it is the differance in the density of the air on top of the wing verses the air on the bottom of the wing. As the air on top of the wing speeds up to cover the larger distance it has to cover to pass the top of the wing its density greatly drops while the air on the bottom of the wings density remains the same. Because of the drop in density above the wing and the same density under the wing there becomes a vacuum above the wing causing the denser air below the wing to push the wing up.

This relates to the venturi on the skimmer in that it takes more vacuum to over come the head presure in the skimmer so the actual size of the air would remain the same while its density would be lower resulting in a reduction in the mass of the air entering the venturi. Once the air is removed from the vacuum its density will be dictated by the head in the skimmer.

Wow that hurt but I think its right.
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Right but you could buy a high pressure air pump and force feed it.
I put the extra 2 foot on my skimmer and I don't need an air meter to tell there is a differance. It makes a huge differance in the amount of air. In light of this I am going to redesign the lower part of the skimmer.
It is a recirc. Its being fed with a mag 12 right now. The orca pump is recirculating at a rate of about 2600GPH and the mag 12 is doing about 1000GPH. I did all the mods I'm going to do to it right now. I didn't have any pvc so I couldn't raise the pump up any to see if that will help any with the higher head set up. I might do it this week tho.
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