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Thread: Microstrainer help!

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    DennisH's Avatar
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    Microstrainer help!

    Okay, I finally got around to installing a vortex microstrainer (Sweetwater) in a gravity fed 40" vortex cone filter. The pond is approximately 18'x18' and 3'-4' deep, estimated total gallons are 8500-9000 and I have a 4" line running from the bottom drain to the filter. I am using a W Lim Wave I 1/4 hp pump to draw from the vortex. When I started up the pump the water pulled from the tank so quickly that the microstrainer walls start to collapse and the water level drops too fast to keep the strainer afloat. It would appear to me that the pump is too powerful and is pulling water too quickly. I would have thought that the 4" line running into the filter would supply plenty of water but it never occurred to me that the strainer couldn't pull the water through fast enough. Changing pumps is not an option - is there anything else I can do to remedy the situation.

    I apologize if this has been discussed before but searching through the forum has proved daunting.

    Thanks for any help!

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    How deep is the 4" line from the pond to the vortex? What is the distance from the pond to the vortex?
    Tom





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    How big is your pump, in gph? And how much does the water drop in the vortex when you start the pump?

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    1/4HP Wave I is 6000 GPH.
    Tom





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    The 4" line is buried roughly 4 1/2 feet deep and approximately 15' from the drain to the vortex. The water drops less than a foot. To be fair, I was trying to get the thing operational as the sun was setting and the mosquitoes were eating me alive so the water drop is just a guess. I do know the suction on the 2" line to the pump was pretty powerful as I kept trying to keep the strainer on. Hopefully, I can work with it some more this evening before it gets dark.

    I should mention that I am also running a Savio skimmer to three sand/gravel filters that are working beautifully (thanks, Birdman!). The purpose of the vortex is strictly for filtering out the bottom drain muck. If the the microstrainer fails to work, is there some other option for the vortex that I can consider since it is already installed?

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    Quote Originally Posted by DennisH View Post
    ...If the the microstrainer fails to work, is there some other option for the vortex that I can consider since it is already installed?
    Kind of a pickle, for sure. For a settlement tank to work, it has to be slow enough to settle. So probably the flow through the thing is just too much. I put a 5 gallon bucket on top of the standpipe in my SC, punched 1000 holes in it and filled it with Kent Wallace bacti-twist media. It works great! I only pull about 1000gph through it, it's a 55 gallon barrel.

    What's the capacity of the cone? 100g? Prolly all you can pull through that bugger is 2-3000 gallons and get any settling at all. Anything that restricts the flow is going to cause the same draw down problem.

    All I can suggest is to plumb another source line to the pump. With a valve, let the pump pull about 2000gph through the settlement cone and get the rest from a midwater pickup.

    steve

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    Yes, I didn't do my homework very well. The cone is a Koi-Clear V-105 which I assume is about 100 gallon capacity - I can't find anything anywhere that states so definitely. It came with the round black matala filter that if all else fails I may consider using to filter out large particles from the bottom of the pond and let the s/g filters do the rest of the work.

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    Can you install a ball valve on the exit of the pump to slow the flow a little?

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    6000 gph is to much for one 4" bottom drain. That's what's causing all your draw down. 3500 gph is more common for one 4" BD, and this will settle out better also.

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    How many spray bars are on the micro-strainer and what mesh is it? The spray bars should take 1000 to 1500 gph so the most flow you should be taking out of the tank is about 5000 gph which includes the amount returned through the spray bars leaving the total outflow at about 3600 gph. A ball valve on the outlet line after the tee for the spray bars would be the best choice. You could restrict the flow and force more volume through the spray bars.

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    Sorry, Kent, I just now saw your response from four days ago. There is one spray bar and the mesh is 250 microns. I have a ball valve attached to the outlet line after the tee and before returning to the pond. Are you saying I could increase the flow to the bar and possibly reduce the pull from the tank?

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    Dont ball valve your pump down. Find another way. Birdman please quit blaming 4" pipe for peoples flow problems. Its just not true. Pull down is NOT the enemy it is your freind you just have to use it wisely.
    Remove your prefilter and run your pump wide open to see if your config can keep up with it. If it can then you know its ALL prefilter problems. If it can not keep up then we need to replumb your vortex with inlets lower. I know that when you think of particles and screens you think that smaller is better but its not the case. Compared to the hassle that comes with 250micron/benifits of it over 500micron its not worth it. Here is why:: Assume for a moment you had nothing but a mechanical screen filtering your pond. All those particles that get through the screen get pumped back to pond right... This makes the water cloudy. Now do you care if its cloudy from 500micron debris or 250micron debris? Truth is cloudy is cloudy whether 250 or 500 micron particles and some OTHER method is needed to get rid of either size particle. Now comes all the down side of 250micron over 500 : Harder to get the flow rate needed/desired:: Its not as rigid and therefore collapses easier. Clogs faster and easier. I know we all think (at first) that smaller is better but it only adds negative effects in the long run. Your sand/gravels dont care if its 500 micron or 250micron they can take care of either just as easy and that is where your clarity is coming from NOT from a 250 screen over a 500micron screen. If you bought a really expensive prefilter and can not change it Im sorry to hear that. If you can change it to 500 do it.
    Lets start with that stuff for now.

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