Kingston Pools and Hot Tubs – Filter Sizing

Choose the right filter. The correct filter size depends on the size of the pool. To maintain a good water clarity you must run the pump each day so that all the water in the pool is turned over. All filters have gallon per minute design rating and turnover rate. The minimum turnover rate is one that turns over the entire pool once in 12 hours. A turnover rate of 8 or 10 hours are the typical sizing rates for pools today.

Choose a filter that would at a minimum turn your pool over in 10hrs. With filters it is okay to go bigger – except sand filters wont backwash properly if flow isn’t high enough. Larger filter areas will help maintain good water clarity.

  • To help your selection process, a list of common pool sizes and their respective gallons and a list of popular filters sizes and their ratings.

For example: A 24 ft round above ground pool has approx 13,500 gallons. A Hayward S166T Sand Filter has a 10hr turnover rate of 18,000 gallons and would work well with this pool.

The correct filter for your pool will be one that is appropriately sized based upon the volume of your pool, the flow rate of your pool pump and the surface area of your filter media.  Most pool pumps have the ability to turnover the water much faster than this which is why some people prefer to use two speed pumps. 2 speed pumps are effective at meeting minimum turnover values while using as little electricity as possible.

Always make sure that the flow rate of the pump does not exceed the maximum design flow rate of the filter. If the pump is too powerful it will cause too much agitation of the sand inside the filter and some sand will go through the multi-port valve and eventually appear in the bottom on the pool.

The actual equation used in calculating filter sizes is pool capacity in gallons divided by the desired turnover rate in hours and this will give you the minimum flow needed in G.P.H. Divide this number by 60 to get the G.P.M that your pump needs to provide to meet the minimum filtration rate for your pool.

The filter that you choose should have a maximum designed flow rate approximately 15-20 percent higher than the calculated G.P.M that your pool pump supplies.

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