How to build above ground filter using pond liner.
Note: My methods of filter construction have been improved since this filter was built. Please review newer consultation projects to make sure you see the latest and greatest ideas.
The great thing about using pond liner to build a filter, is that you can build the filter any size necessary. Liner Filters are also easy to blend into your pond system. In the following instructions I will show you how to build a 120 gallon settling chamber and 100 gallon above ground filter system. This filter is upflow design, and has 8 cubic feet of media for bacteria to colonize. The recommended flow rate for this filter is 1200-3600gph.
Design
Materials
| Qty | Description |
|---|---|
| 10 | 2x8x8' Construction grade lumber |
| 2 | 2x4x8' Construction grade lumber |
| 3 | 6' Deck Boards |
| 1 | 4x8x1/2 Plywood |
| 2 | 10x10 45 mil EPDM pond rubber |
| 1 | Box of 3" screws |
| 1 | Box of 1" screws |
| 1 | 18" of 1 1/2 flexible sump pump hose (or other hose as appropriate) |
| 2 | 6" length of 4" diameter PVC pipe. Used to connect the settling chamber to the pond, the second is used to connect the settling chamber to the filter. |
| 1 | 4" length of 3/4" diameter PVC pipe. Used to connect the drain line connection in settling chamber |
| 1 | 4" Sewar elbow. Used to direct the flow of water upward in the settling chamber. |
| 1 | 3/4" PVC valve |
| 2 | 1" Stainless Steel hose clamp. For the pipe boot to the drains. |
| 1 | 2" Stainless Steel hose clamp. For the pipe boot to the pump. |
| 4 | 5" Stainless Steel hose clamp. For the pipe boot to pond, and from settling chamber to filter. |
| 4 | 1/2" CPVC Elbows |
| 6 | 1/2" CPVC Tees |
| 3 | 1/2" PVC Pipe 5' lengths |
Assembly
- Build a 32" square by 32" deep chamber out of wood. Use 2x4 blocking and plywood triangles to give the bottom a cone shape. Line it with rubber. Use the same principal as is described in the Settling Chamber.
Note: Before you attach the rubber, make sure you have pre-drilled the holes for your drain line, line to connect to filter, and line to connect to bottom drain of pond.
- Attached your pipes using a Pipe Boot. The water that enters the chamber from the bottom drain should enter the chamber through the elbow up. Do not vortex the flow. This is not a vortex chamber. Vortexing the flow will not be effecient in this design. The flow going to the filter should have a small diameter screen, preferrably a self-cleaning microscreen. An alternative (shown in photo) is a screen made out of a 5 gallon bucket and aluminum window screen.
- Build a second chamber identical to the first. This chamber should have a V shaped bottom, not a cone shape. It should have one 4" line at the bottom where water enters from the settling chamber. It should have one 1 1/2" line at the top where the pump draws water.
- Build a grid out of CPVC pipe to support the filter mats.
- Insert Matt Material.
- Attach a slotted pipe to the pump intake. This will provide a balanced draw of water through the filter.
- Attach a pump and return piping back to the pond.
- Attached your pipes using a Pipe Boot. The water that enters the chamber from the bottom drain should enter the chamber through the elbow up. Do not vortex the flow. This is not a vortex chamber. Vortexing the flow will not be effecient in this design. The flow going to the filter should have a small diameter screen, preferrably a self-cleaning microscreen. An alternative (shown in photo) is a screen made out of a 5 gallon bucket and aluminum window screen.