We designed our filter using a combination of things we read in books and
information we learned from the internet. The
filter is made using a 100 gallon Rubbermaid livestock watering tank. This
tank is fish safe and comes with a drain hole at the bottom. We added a
PVC shut off valve and PVC pipes to the drain. This lets us back flush the filter
now and then. The filter
is located directly behind the waterfall so that the water can be
easily returned to the pond at the top of our falls.
Our filter was designed so that the water will move up through lava rocks
with a few filter pads
at the top. A submersible pump pushes the water to the top of
our filter using the black hose you see in the photo. The water then
goes down through the center of a 4 inch PVC pipe. This helps add
oxygen to the water as it shoots into the PVC pipe to the bottom
of the filter. We drilled many holes at the bottom 6 inches of the pipe to allow the water to
flow into the filter. As we pump water into the filter, the
water moves up thru the lava rock. The filter pads at the top help to
stop any sediment before the water exits through the two
outlets at the top into our stream and waterfall.
We used two gasket sealed PVC outlets and 3 inch PVC pipes to build the
drains on our filter. We had to carefully cut two holes in the side of
the filter tank. The PVC outlets come with rubber gaskets and
separate into two pieces, one for the inside and one for the outside of the
holes we cut. When they are screwed back together the gasket compresses against
the filter to create a water tight seal. We also covered the drains with
bathroom silicone to protect from leaks.
This photo shows the drain outlets in place. You can also see how we
use plastic lighting "egg crate" to hold the lava rocks off the
bottom. We stacked old bricks to support the egg crate about 6 inches from the
filter bottom and filled the filter with lava rocks. The heavy dirt accumulates in this
area under the plastic grid where it
can be flushed out by opening the drain and squirting a garden hose down the
sides of the filter.