A Biofall filter is built into the top of a waterfall. This is considered one of the best types of filters for medium to large ponds. It combines a large filter pad with a good amount of biological media. When properly installed this filter type is easy to maintain and nearly invisible. It needs to be installed at the same time as the waterfall since it is incorporated into it.
Steps 1 - 5: Waterfall Installation
The biofall has to be installed into the top of the waterfall. If you are installing the waterfall from scratch refer to the Installation - Waterfalls and Streams link Steps 1 - 5) for the first part of the installation.
Step 6a: Digging
Dig out a hole to match the shape of the filter. If the waterfall is on flat ground you will not need to prepare the ground beforehand.
Step 6b: Leveling
Place the biofall into the hole and check to make sure it is level. You may need to pull it back out several times to make small touches to the shape of the hole until it fits properly. You want the unit to be tilted slightly forward to help prevent water running down the front. The front should be 2 fingers lower than the back.
Step 6c: Tubing Hookup
Attach the tubing to the plumbing parts that fit into the hole in the bottom.
Step 6d: Liner Attaching
Apply seam tape to the front and around the sides of the unit. Peel the back off the seam tape and press the liner firmly into place. Then carefully lower the biofall back into place.
Step 6e: Backfilling
Step 7: Rock Stacking
This is one of the hardest and most time consuming steps in the process. Start at the bottom and work your way back to the top. Make sure every rock you choose fits into its proper place well. Each rock needs to be stable before you go on to the next. If you can't keep a rock from wobbling, pull it out and find another to go into its place. Make sure the height of the rocks are consistent and that they are level all the way across. DON'T BE AFRAID TO RIP IT ALL APART AND REDO IT!!! If you find that you can't make the rocks fit tightly, or you find that the steps aren't the right height, you will want to pull the liner back and re-carve the dirt. I know this is a lot of work but leaving this done poorly is just asking to have to redo the whole thing in 5 years.
Step 8: Seaming
Use double-sided seam tape to attach the liner where the waterfall meets the pond.
Step 9: Foaming
Once the waterfall is completely built and you are satisfied with the look, it is time to seal the rock with expanding foam. Dampen the rock with a hose. Run a bead of foam into every crack that the water will run down. Run through an entire can before stopping. After 20 minutes, a half-used can is worthless. Do not touch the foam until it is dry. Wait 24 hours to cure.
Step 10: Excess Foam Removal
Once the foam is dry go back and pop off all of the excess that is protruding from the rocks. You can use a knife for this but it is often easier to just pull it off by hand.
Step 11: Turn it on!
It's time to plug in the pump and enjoy your handy work.