Commercial Filter Sizing
The filter system is one of the most important parts of the swimming pool circulation system. Along with the pump(s), the filter system must be sized correctly to safely and effectively filter the water.
There are (3) main filter types that are currently used for filtration of swimming pool water. High-Rate Sand, Cartridge, and Diatomaceous Earth (D.E.). For commercial pools, High-Rate Sand is the most common so, we will focus on the correct filter sizing using a High-Rate Sand Filter System. There are advantages and disadvantages to each type of filter system. We will not be focusing on the filter types in this article but the filter sizing. Let's get started!
Let's start off with a 100,000-gallon commercial pool. If the pump size is sized correctly, to obtain a minimum 6-hour turnover rate (code in most jurisdictions) the pump(s) must obtain a minimum flow rate of 280 gallons per minute (GPM). For effective filtration to be assured, the sand filter square footage must be able to accommodate between 15-20 GPM per square foot of filter area. This filtration rate is part of the NSF50 Standard which commercial pools are held to. We also need to look at what the pump(s) maximum flow rate is to size the filter correctly. Time to do some arithmetic!
Most 36" Sand Filters have a filter area of approximately 7-sqft. So if 36" Filters were to be used, you would need 4 total filters to be able to accommodate and properly filter the water in our example
Proper sizing of all components of the circulation system is critical to assure pool water safety and sanitation as well as clean feeling and looking water.
**Always verify local health codes**Brad Dowsett
Commercial Sales Manager
Pool & Electrical Products LLC