Filter Sizing and Flow Rates
There are three common pool filter types – sand, cartridge and Diatomaceous Earth (D.E.). All three of these pool filter types will keep your pool and spa clean, but you should consider the needs of your specific application, your other equipment and plumbing size before making a selection.
When choosing a filter type and size, we recommend enlisting the help of a pool professional to ensure the proper products are selected for your pool. Our pool pros will take into consideration the weather conditions in your area, the types of debris that can land in your pool, and they will also evaluate your entire application – how many gallons your pool has, your plumbing size and the needs of and types of other pool equipment you have.
Tip: An undersized pool filter will render it ineffective and lessen its life; the larger the filter, the longer the time between cleanings.
Pool System Plumbing
The first thing you want to check is the pool system plumbing. For instance, the maximum flow rate through a 1.5 inch PVC pipe is 44 gallons per minute (GPM). Even if you have a pump that can move 100 GPM, it won’t do you much good if the piping will only allow 44 GPM through it. An oversized pump not only wastes energy and money, but it may damage other equipment in the process.
The Right Filter
The correct filter size depends on the size of the pool. To maintain good water clarity, you must run the pump long enough each day to filter and sanitize the water in your pool. All filters have a GPM design rating and a turnover rate. A turnover rate of 8 or 10 hours is a typical sizing rate for residential pools.
All filters have flow requirements. D.E. filters are normally rated at 2 GPM per square feet (sq. ft.) of filter area for maximum flow. This means a 48 sq. ft. D.E. filter will have a maximum flow rate of 96 GPM, and a 60 sq. ft. model will be rated at 120 GPM. So if you have a pump that is going to flow 100 GPM, you would need to go to the 60 sq. ft. D.E. filter.
For a sand filter, it is best to look at the flow requirements of each filter as they can vary from 15 GPM per sq. ft. and higher. Just make sure the filter you choose can handle the flow rates needed.
Cartridge filters are becoming increasingly popular due to their eco-friendly operation. These filters don’t need to be backwashed and can save thousands of gallons of water each season. You should always adhere to the manufacture’s maximum flow rates and be sure not to size a cartridge filter too small as that may cause short cleaning cycles. The best way to determine flow rates for cartridge filters is to use the formula of 3x the flow rate for minimum, and the manufacture’s rating for maximum. The larger the cartridge filter, the longer the cycles between cleaning becomes.
Why Work with A Pool Professional?
This is quite a bit of information to digest and your best bet is to talk to a pool professional to ensure you are using the appropriate products for your investment. With the help of a pool professional, you can be well on your way to receiving the best water clarity and to using the most efficient products in terms of energy use and water conservation.
Remember: Installing a filter too small for the output of the pump could cause costly damage to your filter.
Need some help locating a pool professional near you? Check out our dealer and servicer locator.