What determines if a filter is “gravity” or “pressurized”?
There are different types of filters you can purchase or make for your pond. The question you need to determine is if you want to push or pull water? Most ponds that push water have a pressurized filter, similar to a swimming pool filter. Between your pond (body of water) and a filter container is a pump that will take the water from the pond and push it through a filter and then back to your pond. If a filter is not a closed container, chances are the water would spill or pour out the top instead of going through a pipe back to your pond which would be a problem. The filter needs to be a closed system, water tight, that would only allow the water to be pushed back to the pond through a pipe. In a closed system, you are pushing lots of water through a small container then through pipes. Pressure builds up in the container and the filters are designed to handle the pressure. These are often bead or other media biological filters. In a gravity system you are pulling water. You have your
