Webster’s New World Dictionary defines pressure as “pressing or being pressed, compression, squeezing.” In the hobby of outdoor ponds a pressure filter is an enclosed, external filtration system with pond water pumped into a closed container to circulate before it exits. The container is not open to the outside air, therefore putting the water under a degree of internal pressure – more like a can of juice than a pitcher. Proximity to the pond itself is limited only by plumbing.
Cleaning this type of filter is done by back flushing the filter – injecting water in what had been the exit to flush waste out of a drain placed near or below the inlet. Pressure filters are not designed to deal with large particles and require the pump to be placed on the inlet side of the filter. Each manufacturer has slightly different specifications. The pressure within the tank may be very high or lower, the filter media very fine or of much looser composition, bead, tube or of a pellet shape.
Pressure filters will work on all pond systems, although they may be more filter then you need in a water garden. In a water garden you also have to deal with the dirt that the plants are rooted in, and the dead and decaying plant leaves and flowers. The pump would require a large prefilter ahead of it to catch the vegetable waste. A pond with fish and plants, even just an ornamental fish pond will also benefit from a prefilter – a mechanical filter of any type to screen out the solids. The rest that is not screened out will be ground up by the action of the pump and shorten the effectiveness of the pressure filter.
Originally a pressure filter was of the sand filter type used in the swimming pool industry. It was used to “polish” the water by forcing the flow through and among the grains of sand.
One disadvantage to sand filters is that large particulate matter can clog the filter and after some time the sand could compact, leaving “channels” for the water to flow, decreasing its efficiency.
In the 1990’s the bead type filter came on the market. It is a low-pressure type filter where the water swirls within the filter media of small plastic pellets that host the bacteriological portion of a filter. In a swimming pool, there is no bacteria – the chlorine takes care of that. In a fish pond or even a water feature the bacteria keeps the water clear by consuming dissolved fish waste or plant waste that would encourage excessive growth of algae. The positives of the bubble bead were that it was self contained, small footprint, and easy to clean. It could look like an external water heater, take up about the same amount of space, and cleaning was simply closing a few valves to the pond, opening the drain, running the waste water until it ran clean, and refilling the filter with pond water. The floating beads that hosted the bacteria would come rattling down through an hourglass constriction in the center of the tank knocking any accumulated dirt loose to be dumped out, and when the tank was refilled, up they went to float again.
Current technology has taken the system and improved it even further, retaining the small footprint and the ease of cleaning. The filter media has changed with each manufacturer, with the goal to provide the maximum amount of surface area so the filter can be rated for larger ponds with the same small footprint. Changes have been made in back flush design, bio material shape and construction and efficiency.
Things to take into consideration, with a pressure type of filter.
The pump needs an excellent prefilter before it. A leaf trap will work, but remember that leaves and food pellets going through the pump are harder to filter out, leave more of a residue in the media, than catching them first before they are pulverized.
Remember that the pump itself must be engineered to provide and sustain a higher pressure than one designed for an open-air filter. There will be a back pressure. Pay attention to the manufacturer’s specifications and recommendations on both the pump and the filter. The wrong pump will burn out sooner, leaving you with an unhappy customer.
Consider this filter as a water polisher first and then a biological filter. IF used as a biological filter the water flow needs to be monitored to linger long enough within the media to allow the bacteria to do a thorough job. The bacteria is aerobic and needs oxygen, the pressure filter does not have exposure to oxygen in the same fashion as an open-air filter does. It is also not a mechanical filter and if used as such it will clog more rapidly resulting in wear on the pump, more frequent cleaning and reduced efficiency. A properly maintained prefilter will allow a pressure filter to become capable of higher pond water turnover because the media is constantly circulating in the water flow. If the media becomes packed from improper cleaning or lack of a prefilter, the water going through the filter may channel, creating dead areas (anaerobic) and efficiency will decline.
For the majority of pond systems the addition of a pressure filter from the initial design or as an upgrade/retrofit is not difficult. The addition of a bypass from the pump to divert water to both open air and pressure filters is merely a function of additional plumbing.
A pressure filter is a good option for ponds, especially with the filters’ smaller footprint, neater appearance and ease of cleaning. The closed system is easy to adapt to ponds of all sizes. An increase in the units’ size is minimal compared to open systems. And with the advances in newer technology of filter media, water current efficiency and pump technology such filters should be considered, especially when crystal clear, “polished” water is desired.
See images of filters by Aquadyne, Emperor Aquatics, GC Tek, Russell Technologies, SeaGate Filters and W. Lim Corporation
POND Sources Directory: Pressurized Filters–Manufacturers and Distributors
Aquaculture Systems Technologies
Easy Pro Pond Products
See ad on page 10.
Emperor Aquatics, Inc.
Fluid Art Technologies
302 S Sandy Ln, Unit 5
Chandler, OK 74834-9134
866/712-7007 • firstname.lastname@example.org
See ad on page 36.
Koi Camp Aquariology
See ad on page 37.
Misty Mountain Aquacultural
Patio Ponds LTD
Pondmaster Pond Products
See ad on page 20.
Suburban Water Gardens
W. Lim Corporation
Aquaculture Systems Technologies
Aquarium Life Support Systems
Aquarius Irrigation Supply, Inc.
Blue Thumb Distributing, Inc.
See Business Card ad page 41.
Castle and Carmel
Coastal Pond Supply
Deep Discount Pond Supply
Holmes Farms, Inc.
See ad on page 37.
Koi World Connection
See ad on page 15.
The Asla Group
The Water Garden
Water, Earth, Wind and Fire