The Spiral Vortex

(Retrofitting a Settlement Chamber)

I recently discovered that my little vortex was just *too* small for my microscreen prefilter. So, I decided to replace it with a larger settlement chamber, instead. The theory was that the prefilter operating in a small volume caused the filtered material to concentrate and a lot of it would continually impact the screen, until it broke down enough to pass through it. The stuff in the "soup" that didn't eventually pass thru the screen would become so concentrated, that a screen clog would occur every few days, unless I used an inordinate amount of water in the spray arm system.

But the prefilter was *supposed* to make life easier!

So, I got to digging. And my intention was to make a settlement chamber that was about 10% of the pond's volume, so I would get the weekly water change done, every time I cleaned it out. But, I guess I got carried away, as the settlement chamber now holds a little more than 30% of the pond's volume! So, I over did it just a little. . .

The new settlement chamber is gravity fed from the pond by a 3 inch bottom drain and a skimmer, also gravity fed on another 3 inch line. It works great, but I found that I had to use the spray arms on the microscreen prefilter to rotate the drum. I don't mind a slight angle to help it go, but too much angle reduces the cleaning action of the spray. So, I had to come up with a way to get that "vortex" action, in a square chamber. (4 ft X 4 ft, 3 1/2 ft deep.)

Here is what I came up with. It may look a little odd, but around here, it just fits right in!

Frame made of 1 inch PVC, drilled to let water fill it. Spiral made of corrugated PVC sheet, the kind you'd cover a patio with. Cut into panels, over-laped and glued. The idea is to direct the water into the spiral, where it will flow around the interior wall, rotating the filter drum. After one trip around, the water and it's solids, exit the spiral, where the solids can settle out.

In this view, you can see the "axle" pipe in the center of the filter drum, and the dual spray arms. Water is flowing counter-clockwise. Water enters the exit from the spiral at the 5 o'clock position, in this picture.

The short pieces of 1/2 in. PVC pipe (at 7 o'clock and 5 o'clock,) and the long screws seen, are stand-off's used to form the exit of the spiral. You can see the 3 in. pipe entering the spiral at 4 o'clock. It approximates a tangential entry. The exit from the spiral needs some attention, as it does tend to narrow down a little, in places. The white stand-off at 5 o'clock is at the end of the exit. The spiral ends here.

Notice that the support for the spray arm is temporary. Little, if anything, is fastened down or glued on this system, as it *is* experimental and can be moved/adjusted, when needed, or just to "see what happens."

I suspect that a *multi-turn spiral* would work in a similar settlement chamber, without a microscreen filter, very much like a standard vortex. It would be interesting to see it done, with a center outlet. Also, this corrugated PVC material could be used as a "laminar flow plate," to enhance a standard vortex, with a side exit.

I've used this same material, cut to length and stacked with spacers, to make a horizontal flow biofilter. Not the most efficient material, as it has a low surface area compared to other media, but it does work! And if you have the room to use enough of it to get the surface area you need, it's price makes it a good choice. Very easy to clean!

Back to the DIY home page