POOL CALCULATOR ASSUMPTIONS

Pump Flow: One cubic foot of water contains 7.481 gallons of water. While some prefer complete turnover of pond volume in gallons every hour, many watergardeners successfully use half that rate, turning their water volume over once every two hours. Therefore, pond volume in gallons divided by two equals desired pump flow in gallons per hour. (Actually, because of mixing, complete water turnover takes several days in either case).

Bio-filter size: For flow through biofilters, (the kind dealt with here) the Tetra Encyclopedia of Koi recommends a filter contact time of 10 to 15 minutes. The assumptions contained herin reduces this downward to a range of from 5 to ten minutes. In the case of a 10 minute contact time, a water flow of 1,000 gallons per hour would require a filter volume of 167 gallons ( 1,000 gallons per hour divided by 60 minutes equals 16.67 gallons per minute times ten minutes equals 167 gallons).

Mechanical Filter Size: It is assumed that most watergardeners will want to include mechanical filtration as part of their pool design to simplify maintenance. The mechanical filter area recommended here is based on pump flow in gallons per hour times .01667.

Vortex or Settling Tank Volume: A settling tank or vortex tank is useful in removing large particles from pool water prior to mechanical filtration and allows the mechanical filter to be cleaned less often. Vortex or settling tank volume is set at one per cent of pool volume.

Pump plumbing: As flow increases within a pipe, resistance to flow increases, so as required flow rates go up, larger diameter pipe is required. This relationship is not linear, but can be expressed in the form of the following graph.

Gravity Plumbing: Just as with water flow under pressure, gravity flow resistance increases as flow velocity increases. Generally, the pipe diameter for gravity flows are larger than for pumped (pressure) flows, as evidences by the following graph.

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Last modified on September 6, 1999