Q about DIY Fluidized Filter Bed

[nfored]

So from the FFB's I have seen it looks like a round container with a intake that goes almost to the bottom. The container is filed 1/3 way with sand then sealed air and water tight. Water is pumped in from the top to the bottom and returned via pressure to the tank through the outlet on the top.

So my question is what would be bad about buying a strong walled 55 gallon drum, filling it 1/3 full of sand and installing the piping and sealing it up. then powering it with a inline high pressure water pump.

basically building a large diy pool sand filter I guess.

 

[wow_it_esploded]

If you can get a good enough pump and a strong enough drum I think that would be a dandy idea... I imagine it could support thousands of gallons of water!

 

[mrunlucky07]

As you get larger in diameter it takes exponentially larger pump to move enough water to evenly fluidize the sand. According to Aquatic-eco a 24" diameter cylinder requires about 4500gph.

IMO a much better option is a sand/gravel filter. It is a drum with gravel from course to fine to sand, upflow from the bottom of the barrel. Good with about 200o gph. In the bottom you put an air manifold and then hook up a blower/shop vac that forces air through to clean it when necessary. All the air rushing up from the bottom blows all the dirt out and through a waste output when cleaning. Easy clean, good bio and mechanical.

 

[Dr Joe]

An FFB is not a pool sand filter, pool sand filters filter from the top down and out and don't hold the sand in suspension like the FFB.

A normal barrel that will hold the weight of the water and sand is all that's needed since it is not being pressurized.

The trick is the bottom (of a big container like a barrel especially) should be cone shaped (like a funnel) so the inlet is directed to the center of the cone, lifting / mixing the sand continuously (no dead spots). Remember, the object is to just mobilize the sand.

If you can't get or make a cone shaped bottom for the container, you need to get creative with jets at the bottom. If they create to much velocity the sand will blow out, plus have more back-pressure. If you loose some pressure (for a multitude of reasons) with these the sand starts to settle .
Dr Joe

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