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Skimmer Modding


Neogenesis
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Hey guys, 

 

I've been pretty quiet around here lately with the new job, but I've taken on a project, and I'm unfortunately not finding a lot of info, or I'm not searching the right terms.

 

 

So......on my big recirculating Geo skimmer, the Sedra9000 is getting more than a little worn, so I've decided to upgrade it and put on a DC needle wheel pump.  The problem is, there is no plumbing included with it to get air into the pump, like seen below.   Without having to tear my Sedra apart to see how it's build, I need to keep it running due to bio pellets, does anyone have experience with building one?  I've been able to build the needing plumbing to hook it up, but need to figure out how to get it to suck air in.  Has anyone successfully built a venturi?

 

 

20160121_102232_zps1elknx2p.jpg

 

 

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Very nice.....that appears to be a in sump skimmer right?   I'm dealing with an external recirculating.....it it's a bit more tricky.   I was playing around today and think I've found a solution.  I'll post up pics after some testing.

 

But basically took some 1" pvc, a piece of 1/2" pvc, turned down the outer diameter until it would fit inside the 1".   The I used a rasp to give the front edge a bit of an angle to help water flow and acclerate it through that section even more, then just dropped the tubing into that section.   Testing in tap water seem to work ok, so I'm going to push forward with all the other work to get this dc pump installed on the skimmer and see what happens.  I figure even if it works just ok, it's still better than the Sedra currently is at it's best.

 

This is the picture that helped it all make sense.  So that's what I was aiming for with the 1/2" pvc insert I made.

Venturi%20Principle8d2a3ee030e34b1abc437

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  • 2 weeks later...

There are two types of venturi out there that work slightly differently.  The one you have above is a true venturi - a restiction in the tube that accelerates flow, causing a drop in pressure that allows the air to be drawn in by the flow of the water.  You see these more often in applications on the pressure side of the pump - Beckett and Mazzei.  The other one is pictured here..

 

 

You see a lot of this style on the inlet side of the pump.  I think its more efficient then the above.  I've made several of these on a 3-D printer and they work fantastic.  Basically, you're restricting water intake and the pump sucks air instead so you're really not relying on the water flow to generate the air suction (not a true venturi).  Its similar to the above, but can be implimented in a smaller space and I think is easier to design/make.  If you look at Bubble Magus and RO skimmers they use this style.  I start with about a 55% restriction (if the pump intake diameter (A) is 1" then the restriction diameter ( R ) is 0.45".  This seems to be a good starting point to get good air draw/bubble action.  Use an air flow meter to measure liters/hour of air intake and adjust the restriction to get where you want to be.  To much air and the pump will fail to start, cavitate or overheat.  To little and you're just pumping water.  Finding the sweat spot can be tricky.  Either design can be used inline as your setup shows, I would put it as close to the pump as you can though.

 

 

post-343-0-50263900-1454635972_thumb.jpg

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