The magic is the duck pen which is pond lined and has a bottom drain that drains water to a below ground level catch basin (sump). A water pump in the sump pumps water to the ducks water bucket. The excess flows back into the sump via the duck pens bottom drain. That’s the basics. There are settling tanks and mechanical filters pads in the sump to help clean the water ( mainly for the Duck Pond and Koi pond which also share the sump).
The external pump outlet is tee’d off into four each with a ball valveto control flow. One outlet goes to the ducks water bucket. One goes to the duck pond. One goes to the koi pond. And one is for the bunnies water dish (still haven’t finished the bunnies self waterer). All water gravity flows to the sump via bottom drains.
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Water goes to the bucket on the right and exits to the sump via a pbottom drain in their pen. The pipe is to the left of the brown Indian Runner (Chewie!!)
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All water flows to the sump which is below the wooden platform where the water is filtered And pumped back to the various places.
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I rely mainly on the plants in the Duck pond and Koi ponds stream to keep the water fresh.
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I love the system, it has worked through all seasons. In the summer I turn up the flow so that it keeps the pea gravel cool for the ducks. In the winter I also increase the flow so that the pipes don’t freeze.
I bet a smaller system with a 55 gallon barrel and a below water bucket catchment would work as well. But I think if you had a pond some creative piping would accomplish the same goals.
edit: check out my coop to get a better overview of the whole setup.