**** Mat/Brush Prefilter Sump ****

Spike Cover sent this in. It is his version of an older, more traditional style of prefilter that works quite well. It is simple, straight-forward, and fairly easy to make and maintain. This is one of those designs that demonstrates that Low-Tech is not only still viable, but has some advantages over newer, High-Tech design concepts.

Here is the text Spike sent with the pictures:

Water flow = inlets -> two racks of brushes (2 rows each = 4 rows total) -> some white matting (not shown) -> some OC foam -> to pick up for pump.

To clean it I just:
Shut off the water pump.
Put standpipes in the 5 inlets.
Pull the brush racks out.
Pull the white mat and OC foam out.
Drain the water in the chamber.
Pull the standpipes 1 at a time to flush the lines.
Re-drain the chamber.
Hose off the brushes, white matting and OC foam.
Put the stuff back in the chamber.
Pull the standpipes.
Start the pump.

Things I'd like to change: * I'd make it bigger, probably 3' X 4' - same depth though, as brushes don't come longer than 2', I think.

* Slope the bottom from the inlets side to the outlet side as crud migrates in the direction of the water flow.

* Figure the pressure drop from the pond to the chamber when it's working (it runs off gravity - skimmers and all) and set the brushes low enough to where only about 1" was sticking out of the water during operation. This would utilize more of the brushes' length.

I clean the thing about once per week in the summer. If I didn't have plants, it'd go at least twice as long, I suspect. FYI, my system is about 3000 gallons with about 2500 gal swimming water for the fish. Hope this was helpful. If you need/want more info, just ask.

Cheers,

Spike

PS, Just put a new filter, pump (additional) and heater on the system. In order to get the flow, I had to open the extra 3" inlet pipe that I normally had blocked.

OK, my comments on Spike's design:

Water can be brought in to the prefilter with stand pipes as shown, through the bottom of the sump, or through the side using bulkhead fittings. If you use bulkhead fittings, put a valve on each input so you can isolate the sump for drainage. If you want to forgo the valves and spend the money on something else, use bulkhead fittings (off-the-shelf or DIY) with female threads, instead of the slip-type. Use an end cap, short piece of pipe, and male thread adaptor to make a plug for each inlet. Make a spare, while you're at it, otherwise, you'll come up short one, sooner or later. An additional valve or plug will be needed on the outlet, as well. This is used not only for drainage, but also when you isolate the sump to work on the pump or whatever comes next in the system.

If your site is too flat to gravity drain the sump, slope the bottom of it to the center, as Spike did, and create a depression where the drain would have been placed. You can put a regular sump pump here to drain the sump, for clean-outs.

This mat/brush prefilter sump can be used with a submersible pump, as well. Just locate the pump about halfway up from the bottom, on the end of the sump where the outlet is shown in the drawing.

In a recent email, I asked Spike about the flow rate through this particular prefilter sump. Here is what he had to say on that:

Right now, I have two 1/4 hp pumps pulling out of the sump. One Lim, one Sequence. The water really whistles thru there. Way too much for really good filtration. Worked OK with just one pump which is what I designed it for. I've checked the Lim pump circuit and it's flowing at a bit over 70 gpm. I suspect the Sequence is running a bit less. So my guess it somewhere between 7500 to 8000 gph. Not bad for a 3000 gal system, huh? The pond is small so I put em on a treadmill for exercise. :)

To see a larger picture, click on any of the thumbnails, below. A new window will open for the larger, slower-loading picture.

The inside measurements are 2' x 3' and I think it's about 3' deep at the shallow ends - slopes to middle where drain is.	Standpipe plumbing, before pouring concrete.
Filter sans water and white matting.	With water (w/o white matting and OC foam.)

Spike cleaning the filter. I really like how the PVC racks make that so easy!

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