Tips on Upgrading Your Pool Filter

If you are trying to figure out what size swimming pool filter to purchase for your pool, things are complicated by not only the different filter sizes but also by the different types of filters. So directly comparing one filter type to another is not an exact science. Here is a breakdown for you on the size comparisons across the three different types.

The first thing to make a note of is that in almost every case going with the largest filter size possible for your pool will pay off. If you have a 20,000-gallon pool you can get away with a 100 sq. ft. cartridge filter but you will be cleaning it every month and you may have water quality issues. Many pools in Florida work with these single cartridge filters and it is certainly rated for that size pool, but I wouldn’t recommend such a small filter. That same pool with a 420 sq. ft. cartridge filter will go 6 months in between cleaning and you will have zero water quality issues and great flow. Water quality issues would be cloudy water, algae and the like.

Here is a good example of this from my pool route. A customer had a 25,000-gallon pool with a 36 sq ft D.E. filter on it. We upgraded his D.E. filter with a 420 sq. ft. cartridge filter. The flow had increased so dramatically that we had to divert half of the return flow to the attached spa so that the pool wasn’t like swimming in the ocean! The flow increased dramatically and all the issues I had with the pool disappeared overnight. So upgrading to a larger filter can really move the needle if your pool is experiencing water quality issues.

So how would you get a good size comparison between the three filter types? I think you have to work off of a ballpark figure since all of them filter the water in a different way. Here is the best guess chart for you:

36 sq. ft. D.E. Filter is equal to a 200 sq. ft. Cartridge Filter and a 150-200 lbs. Sand Filter

48 sq. ft. D.E. Filter is equal to a 320 sq. ft. Cartridge Filter and a 250-300 lbs. Sand filter

60 sq. ft. D.E. Filter is equal to a 420 sq. ft. Cartridge Filter and a 350-400 lbs. Sand Filter

100 sq. ft. Quad D.E. Filter is equal to a 520 sq. ft. Cartridge Filter and a 450-500 lbs. Sand Filter

Since a D.E. Filter uses Diatomaceous Earth (D.E.) the filtration area is very small but highly effective. In fact, D.E. Filters can filter down to 3-5 microns making it the best filtration as far as microns go. A Cartridge Filter can filter down to just 15-20 microns and a Sand Filter down to 30-40 microns. So if you are just comparing filters by how good they filter down to D.E. is the winner. If you are looking at sheer filtration area then the Cartridge Filter is the clear winner. With filtration areas of over 500 sq. ft. nothing compares to it. But since it uses a cloth basically to filter, even though the surface area is greater it doesn’t filter as efficiently as a D.E. Filter.

For ease of use, a Sand Filter can’t be beaten. All you need to do when it gets dirty is backwash it and of course, change the sand every few years. But you don’t need to take it apart and clean it every few months, nor do you need to recharge it every time you backwash it. The sand that is in their stays in there and you couldn’t ask for an easier filter to maintain. If you are looking mainly for ease of use then a Sand Filter should be your first choice.

Each filter type has their good points and their drawbacks. There probably is no perfect choice but if you go with the largest filter for your pool based on the gallons of water, the better off you will be. The larger filter allows for a better flow rate, better overall filtration, and better water quality. Although the upfront cost may be more it will pay for itself over the years in time and fewer chemicals used to maintain your pool. Think about the time you will save with a larger filter in cleaning the filter and also the energy cost as you can run the pool less with a larger filter. And finally, with a larger filter, you will not struggle to keep the chemistry balanced and therefore will use less shock and algaecide over the years.  So a larger filter is a win-win across the board.

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