Learn how to choose a small pool filter and why selecting the perfect size filter is essential for keeping your pool operating efficiently.
Your pool’s filter is what keeps the water clean. It filters debris, dirt, oil and anything else that can turn crystal-clear water cloudy or worse. Selecting the right filter for your pool is about more than just buying a small pool filter for a small pool and a large filter for a bigger pool.
Choosing the wrong filter means you’ll make chemical adjustments more frequently and strain your pool equipment more than necessary. The right filter is one of the most important factors in keeping your pool in tip-top shape. With a filter that's too small, you’ll spend a lot of extra time working to keep the water clean.
If you’re shopping for a new pool filter and you want to choose the right size, here’s what you need to know.
Pool Size and Water Volume
First and foremost, you’ll need to consider your pool size and water volume. Determine how many gallons of water you’ll need to filter. Filters are designed to process certain amounts of water within a given timeframe. Small pool filters are great for smaller pools, but if you choose a filter that’s too small, it’s not going to work effectively. You’ll either burn through the filter and/or it won’t keep the water clean.
If you aren’t sure of your pool’s volume, use one of these formulas to determine it:
Rectangular
Length × width × average depth × 7.5 = approximate gallons
Round
Diameter × diameter × average depth × 5.9 = approximate gallons
If you have an irregularly sized pool, you’ll need to break it into sections and use these formulas to estimate the volume.
Types of Pool Filters
Once you know the volume of your pool, you’ll want to consider the type of filter that’s going to work best for your pool. For example:
Cartridge Filters
Cartridge filters are one of the more popular options for small pools. This type of filter strains water through pleated material, trapping dirt and debris. They’re easy to maintain and offer decent filterability. There’s no backwashing and minimal wastewater. You’ll need to remove and rinse the filter with a hose every few weeks or more often if you notice the water flow decreasing. These filters need to be replaced every few years depending on your specific conditions.
Replacement cartridges like the Hayward SwimClear C200S / C200SC Element (CX200XRE) are manufactured with premium materials designed to meet NSF's high-quality and performance standards. They offer optimal hydraulic efficiency, effective first-pass debris removal, extended filtration cycles, reduced cleaning time and multi-season durability.
Sand Filters
Sand filters are easy to operate and long-lasting. This type of filter requires backwashing, which reverses water flow through the filter to flush out any trapped debris. You may need to do this about every four to six weeks, depending on pool usage, debris levels and water conditions. Sand filters use more water than cartridge filters and don’t always remove the smallest particles.
Diatomaceous Earth Filters
Diatomaceous earth (DE) filters use powder to capture small particles. They give you optimal water clarity because they’re able to remove very fine debris. While DE filters offer the best filtration, they require more maintenance, and you’ll need to replace the DE powder after each cleaning. They’re also pretty powerful and might be overkill for smaller pools.
We like the Hayward Perflex® Extended Cycle D.E. Filter, 27 ft. (EC65A). Its patented Flex-Tube design gives you longer intervals between cleanings because the same powder is used repeatedly. It also cleans without backwashing, saving hundreds of gallons of treated pool water.
Common Filter Mistakes
When you’re choosing a filter for your pool, you’ll want to avoid a few common mistakes, including:
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Buying a filter without checking your pump capacity
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Ignoring recommendations from the filter’s manufacturer
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Selecting your pool filter based only on its size
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Choosing a filter that requires more maintenance than you’re willing to put in
How Do You Know When It’s Time to Replace Your Filter?
If you’re considering switching to a different type of filter but you don’t know if there’s any life left in your old one, how do you know when it's time to replace it? Here are a few signs to look out for:
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Cloudy water not caused by poor circulation or a chemical imbalance
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Filter needs cleaning every few days instead of every few weeks
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Reduced water flow
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Increasing filter pressure
Save Time and Money With the Right Pool Filter
Choosing the right pool filter is about more than just picking something that’s the right size. Your pool’s filter affects the lifespan of your pool’s equipment and how often you’ll need to perform maintenance.
If you’re not sure which type of filter will work best for your small pool, we can help you determine the best filter system for your pool.
