Very effective, but not efficient because of the space taken up by the filters.
These units, when buried in the ground, require less space than the pressure sand system but long term durability can be a problem if there are failures at the welds, or other locations due to aggressive corrosion.
Only manufactured by Paddock.
Vacuum filters require 40% less TDH than pressure systems. They can also double as a surge tank.
Paddock recommends backfilling around the filter. Because the filter is stainless steel, corrosion will occur over time (the welds will be the first to fail). To alleviate these maintenance nightmares, CH recommends a concrete tank that would be approximately 3 feet larger than the tank on the four sides and underneath.
Comparing only the vessels, the vacuum sand filter will cost approximately $10,000 more than a high rate sand filter. However, money is saved because the vacuum sand filter will require less piping, less mechanical room space (if the unit is in the ground), and hair and lint strainers would not be required.
Sand tends to pact. Air purging is required during backwashing to break-up the sand.
The designer has much more flexibility with pressure filters. For vacuum filters NPSH is critical in both clean and dirty filter conditions as opposed to pressure filters where your baseline pressure is whatever head you want to put on the pump. Much closer attention must be paid by the pool operator to vacuum filters. If it is left alone, there is a real possibility of cavitating the pump.
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