By Richard Medina and Abhi Pillai
Cartridge filter manufacturers believe in making the best products available and know it is feasible to provide the industry with different grades of product based on the type of pool/hot tub, geographic location, what water quality challenges (if any) the customers are facing. Unfortunately, unlike other industries, the aquatics sector has a ‘one size fits all’ approach. That said, to get past this ideology, there is a need for a new consumer rating system, which would help consumers and businesses properly size and install pool filtration systems accordingly.
What consumers expect from a filter cartridge?
In a survey conducted by the authors’ company, pool and hot tub owners, retailers, service technicians, and distributors were asked what they expect from a pool/hot tub filter. It was based on three main performance characteristics:
- Clean water (a.k.a. turbidity reduction).
- Longer operational cycle (a.k.a. service life of the product).
- Longer product life (a.k.a. dirt holding capacity).
Today, pool and hot tub filter manufacturers use these parameters of performance to build next generation products for the industry.
No two pools are the same—from the way they are plumbed, their surroundings, and the manner the customer uses them. Therefore, it is difficult to use a one-size-fits-all approach. One good example of this is a 151,416-L (40,000-gal) pool in Florida would use an 11.1-m2 (120-sf) cartridge filter, while the same size pool in Arizona would use a 39-m2 (420-sf) filter. There are a couple of reasons, for this. The frequent sand and dust storms and other climatic conditions requires the pool owner in Arizona to have a filter cartridge system with higher dirt holding capacity compared to someone in Florida.
Until recently, filtration systems for pools and hot tubs were only classified on micron ratings—giving customers a choice between cartridge, diatomaceous earth (DE) grids, or sand filter media. Typically, filters are rated by its micron size, which indicate the absolute largest particle that is capable of passing through the media. Filters designed for applications such as drinking water or air quality are expected to catch debris (to the rated value) as it passes through the filter media. Since there is no expectation for the same water or air to be recirculated, the filtration must happen during the first (and only) pass.
However, this is not the case with pool and hot tub systems. Aquatic filtration systems count on the repeated circulation of the same body of water, which builds a filter cake on the media. Over time, the filter is able to clear smaller and smaller particles. Eventually, all filtration systems will clear the pool to different degrees of efficiencies despite their differences in the initial micron rating.
To explain further, this article will look at the comparison of two filter cartridge systems:
- ‘System A’ housing a single 9.3-m2 (100-sf) filter element; and
- ‘System B’ containing four filter elements of 9.3-m2 (100-sf) each for a total of 37 m2 (400-sf) of filter area.
One would expect System B to perform four times better than System A; however, it is important to understand how each system’s performance characteristics are different.