3D Printing A Self-cleaning Water Filter

No one likes cleaning out water spouts. [NeedItMakeIt] wanted to collect rainwater and was interested in using a Coanda filter that those used on hydroelectric plants to separate out debris. Ultimately, he decided to design his own and 3D print it.

The design uses a sloping surface with teeth on it to coax water to go in one direction and debris to go in another. It fits into a typical spout, and seems like it works well enough. Some commenters note that varying volumes of rain and different types of debris behave differently, which is probably true. However, there are similar commercial products, so you’d guess there would be some value to using the technique.

The water pushes the debris off the slope, so you end up losing a little water with the debris. So as always, there’s a trade-off. You can see in the video that if the water flow isn’t substantial, the debris tends to stall on the slope. Could the filter be improved? That was the point in trying a second design.

It wasn’t a big improvement. That’s where there’s a plot twist. Well, actually, a literal twist. Instead of making a flat slope, the new design is a conic shape with a spiral channel. That improved flow quite a bit. We weren’t clear from the video of exactly where the debris was going with the last version.

Usually, when we think of the Coanda effect, we are thinking aerodynamics. It can be quite uplifting.

22 thoughts on “3D Printing A Self-cleaning Water Filter

  1. We weren’t clear from the video of exactly where the debris was going with the last version.

    The crap falls straight through and goes down the rest of the downspout, presumably to the sewer connection. The idea is to pick off clean water to collect in a rain barrel while letting the crap get flushed away.

    1. Yes, you struggle to beat an enclosed weir type arrangement ie rain water from roof falls into and enclosed bucket and the debris settles with the clean water takeoff higher up. Still I’m going to try this as always keen to experiment…

  2. As time went i understood his problem and wy dont he use a bucket and let water with his tree debris fall into then the debris sink and he collect the water drping from the bucket , sorry that didnt include 3d print.

    1. You are drinking water that is supplied through plastic pipes. Buying different drinks in PET bottles, food in plastic containers. And how is this filter(could be printed with PETG) worse than all of the above?

      1. Who is drinking water out of plastic pipes? Tap water comes from metal pipes typically and it’s tested to be free of any contamination.
        But okay, you have resigned, you don’t care – got it.

    2. Same thought here, as maker we should integrate ecological impact in our creations. It’s seems an elementary consideration (as power consumption / efficiency in other context).

  3. I don’t get it. Is it not the problem at the top on the roof? Usually is at the gutter that gets clogged right?. What’s the point of separating whatever comes out? Just send them their way in the sewer

  4. I’ve seen a much better variant built like a drum sieve, but inverted. The dirty water was poured on top of the sieve. The water goes through into the drum, while the debris falls of when the drum rotates.

      1. So once all the leaves get caught by that, where do they go? The picture of the product alone doesn’t really give much explanation of how it’s expected to fit into the system.

  5. So, I hear the words “jerry rigged half baked, willy nilly, provincial solutions to non issues caused by lacl of proper setup” coming to my lips. Do it right from the start by trimming the trees around your structure and dont let your roof be covered in shmutz in the first place . . .

    My uncle died when he fell off the roof cleaning his gutters. Im sorry it is a touchy subject. Stay safe out there in TV land.

  6. To all those asking questions, this device is a separator, not a filter. He’s separating the water from the debris, saving the water for his plants, and letting the debris fall through to the ground where it dries up an blows away.
    In a filter, all of the flow goes through the filtering mechanism.
    In a separator like this, some of the flow is diverted, and some flow is left to clean the grating and keep it from becoming clogged.

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