I've finally done it! Built my first raft on legs 4' off the ground about 3' wide x 4' long and 18 holes.Set seeds, so in a couple of weeks we put the net pots in and see from there. I've converted a 6" OD PVC pipe as a horizontal net filter by cutting a 2" wide x 1' long window and stuffed it with fine netting (same as Chris used to use as trough covering). As some rafters use both Net and Swirl filters, thinking that this is the place to show some different designs we use in our systems. As soon as i can get some photos I'll post some pics. Anyone care to share?
Found a design for swirl filter and explanation on manufacture if anyone's interested.
The swirl is working well. I positioned it where the top of the swirl is about 4 inches above the raft. The exit pipe is about 10 inches submerged vertically into the raft. It sucks huge amounts of air all the way down into the bottom of the raft! What a bonus to discover that this happens with gravity flow both entering and exiting the raft. I was going to add a small aquarium pump but with all these bubbles i won't be needing it anytime soon. I took some pics below.
We combine a swirl and a net filter in our 80sqft DWC system. It seems to working very well, most of the roots are white and free of crud. From the fish tank, water is immediately routed to a 55 gallon barrel with a slight swirl in it. some bigger solids settle out to the bottom, and they are also visible on top of the pvc piping inside the barrel. there is a spigot to drain the tank periodically. we've only done this twice in a few months. The water is flowing at 2gpm-- more than that and that solids don't seem to settle out. from the swirl, the water goes into a second barrel. this barrel's intake is near the bottom. in the middle of the barrel are a couple of floor buffing pads the fit snugly in the barrel. They consist of lots of microfiber material and act and a filter. there are several different thickness of pads for different levels of filtration. the outflow from the filter tank is near the top, above the filter pads, so the water is force filtered, as it wants to press up through the pads and out the pvc, down to the hydroponic troughs. by now the water is much clearer. it is important to put the outflow on the last tank not right at the surface, but just below it. we used to have the outflow at the top but found that any crud that floats-- mosquitoes, leaves, etc., would get sucked into the troughs.
an additional help is gammarus, common water fleas that are detrivores and help eat junk. this may be why we don't have to clean the filtration tanks too often.
this system is working well for us. i will post pictures soon. good luck on your design and i look forward to hearing how it goes. aloha
Harold Sukhbir said:
Thanks for your encouragement Chris. Looks like I'll have to clean weekly. The first few plants near to the inflow are getting some gunk on them compared to progressively very little to those moving away from here. Bought some heavy shade material which I'll add to the swirl. While the gunking is minimal i still would like to have more efficient filtering. Can you tell me if anyone combines swirl and net in this way?