Quick Summary
- A sand filter uses specially graded filter sand to trap dirt and debris, as pool water passes through the filtration system.
- Sand filters are known for their affordability, durability, and relatively simple maintenance requirements.
- Routine maintenance primarily involves monitoring filter pressure and backwashing the system when needed.
- Filter sand typically lasts 5–7 years before replacement is required, while the filter tank itself can often last 15–25 years or more.
- The biggest advantages of sand filters are their low cost and ease of use, while the biggest drawbacks are reduced filtration precision and water loss during backwashing.
Keeping pool water clean would be pretty difficult without a filtration system. Thankfully, pool filters do most of the heavy lifting behind the scenes, removing dirt, debris, and other contaminants before they have a chance to cloud the water.
One of the most common filtration systems used today is a sand filter. Known for its simple design and relatively low maintenance requirements, a sand filter can be an effective and affordable option for many pool owners.
In this article, we'll explain what a sand filter is, how it works, what it costs, how to maintain it, and the biggest pros and cons to keep in mind before investing in one.
What Is a Sand Filter and How Does It Work?
A sand filter is essentially a tank full of sand that's connected to your pool's filtration system. As pool water passes through the tank, the sand traps debris and particles and prevents them from returning to the pool. This results in cleaner, clearer water.
Most sand filters use #20 sand, or mesh crystal silica #20, but they may also use glass or zeolite. The sand filter tank itself is typically made from fiberglass, plastic, or stainless steel and is durable enough to withstand the high pressure required to run the filtration system.
The process is relatively simple:
- Pool water enters the filter tank and is distributed evenly across the top of the sand bed.
- Water flows downward through the sand, where particles become trapped between the sand grains.
- Filtered water is collected through the laterals at the bottom of the tank. These laterals allow water to pass through while preventing sand from escaping into the pool.
- Clean water returns to the pool through the circulation system.
Over time, material trapped in the sand bed begins to restrict water flow. When this happens, the filter must be backwashed to restore proper performance.
Main Components of a Sand Filter
Most pool sand filters include the following components:
- Filter tank
- Filter media (sand, glass, or zeolite)
- Multiport valve
- Pressure gauge
- Internal laterals
- Plumbing connections
While designs vary by manufacturer, the overall filtration process remains largely the same.
What Size Sand Filter Do I Need?
The size of sand filter you need depends primarily on your pool's volume and your pump's flow rate.
As a general guideline:
- Pools under 20,000 gallons often use a 24-inch filter.
- Pools between 20,000 and 40,000 gallons typically require a 24- to 30-inch filter.
- Larger pools may require a 36-inch filter or larger.
When in doubt, it's usually better to slightly oversize a sand filter rather than choose one that's too small. Downsizing can overload the system and reduce filtration performance.
How Much Does a Pool Sand Filter Cost?
One of the biggest reasons sand filters remain popular is their affordability. Compared to many other pool filtration systems, sand filters typically have a lower upfront cost and relatively low long-term maintenance expenses.
Filter cost
The cost of a sand filter depends on its size, brand, and overall construction. In general, homeowners can expect to pay:
- Above-ground pool sand filters: approximately $300–$700
- Inground pool sand filters: approximately $500–$1,500+
Larger pools require larger filters, so costs tend to increase as pool size increases. Some higher-end models may also include upgraded valves, stronger construction materials, or other features that can increase the price.
The good news is with proper care, many sand filters can remain in service for 15–25 years or more before needing to be replaced.
Replacement Sand Cost
While the filter itself may last for decades, the sand inside won't.
Replacement sand typically costs around $20–$40 per 50-pound bag. Depending on the size of your filter, you may need anywhere from 100 to 600 pounds of sand. For many average-sized inground pools, that works out to about 350 pounds, or roughly seven 50-pound bags.
Replacing the sand isn't something you'll be doing every season. Most filter sand lasts about 5–7 years before it needs to be changed.
Sand Filter Maintenance
Like any pool filter, a sand filter needs occasional maintenance to keep water flowing properly and maintain good filtration performance. The two primary maintenance tasks are backwashing the filter and replacing the sand when it eventually wears out.
Backwashing Your Sand Filter
Over time, material trapped in the sand bed begins to restrict water flow and increase pressure inside the filter. When the pressure gauge rises about 8–10 PSI above its normal operating pressure, it's usually time to backwash the filter.
Backwashing reverses the flow of water through the tank, flushing trapped material out of the filter and sending it to waste. The process only takes a few minutes and helps restore normal filtration performance.
The general process looks like this:
- Turn off the pool pump.
- Set the multiport valve to Backwash.
- Turn the pump back on and run it until the water appears clear.
- Turn the pump off and switch the valve to Rinse.
- Run the rinse cycle briefly before returning the valve to Filter mode.
Always follow the manufacturer's instructions, as procedures can vary slightly between models.
Replacing Filter Sand
Although backwashing helps keep the filter clean, the sand itself doesn't last forever. Over time, the sand particles become smoother and less effective at trapping material.
When the sand eventually needs to be replaced, the process typically involves:
- Drain the water from the tank and remove the filter head.
- Scoop or shop-vac out the old sand from the tank.
- Fill the tank up to the halfway point with water.
- Add sand filter sand according to your manufacturer's instructions.
- Re-attach the filter head and backwash the water for 30 seconds.
- Return filtration to "filter" mode and double-check for leaks.
Because procedures vary by manufacturer, it's important to follow the instructions provided for your specific filter model.
Occasional Repairs
Like any piece of pool equipment, sand filters may require occasional repairs over time. Components such as multiport valves, gaskets, pressure gauges, and laterals can wear out and eventually need replacement.
Fortunately, these parts are widely available and are often less expensive to repair than replacing the entire filtration system.
Advantages of Sand Filters
There are a few reasons sand filters have remained one of the most popular pool filtration systems for decades.
Affordable
Compared to many other pool filtration options, sand filters typically have a lower upfront cost and relatively inexpensive replacement media.
Easy to Operate
Once installed, most maintenance consists of monitoring the pressure gauge and backwashing when needed.
Durable
With proper care, a quality sand filter can often remain in service for 15–25 years or more.
Widely Available
Sand filters have been around for a long time, which means replacement parts, service technicians, and filter media are generally easy to find.
Disadvantages of Sand Filters
No pool filter is perfect, and sand filters do have a few drawbacks to consider.
Doesn't Filter as Finely
Sand filters generally capture larger particles than cartridge and D.E. filters. While the difference may not be noticeable to every homeowner, other filtration systems can sometimes produce slightly clearer water.
Water Loss During Backwashing
Each time you backwash the filter, water is discharged to waste and must be replaced. Over time, this can increase water usage compared to filtration systems that don't require backwashing.
Periodic Sand Replacement
Although it doesn't happen often, the filter media will eventually need to be replaced as the sand becomes less effective over time.
Is a Sand Filter Right for You?
Sand filters have been helping pool owners keep their water clean for decades, and their popularity isn't hard to understand. They're relatively affordable, require minimal day-to-day attention, and can last for many years with proper care.
While every pool owner's needs are different, a sand filter can be a solid choice for those looking for a dependable filtration system without a lot of complexity.
Frequently Asked Questions
How does a sand filter work?
A sand filter cleans pool water by forcing it through a bed of specially graded filter sand. As the water passes through the sand, particles become trapped while clean water returns to the pool.
When should you backwash a sand filter?
Most pool owners should backwash their sand filter when the pressure gauge rises about 8–10 PSI above its normal operating pressure. This helps restore water flow and maintain filtration performance.
How long does sand last in a pool filter?
In most cases, filter sand lasts about 5–7 years before it needs to be replaced. Factors such as water chemistry, sanitizer type, and pool usage can affect its lifespan.
How much sand does a pool filter need?
The amount of sand required depends on the size of the filter. Most residential systems use between 100 and 600 pounds of sand, while many average-sized inground pool filters require about 350 pounds.
How much does a pool sand filter cost?
Most residential sand filters cost between $300 and $1,500 or more, depending on the size, brand, and construction of the filter. Larger pools typically require larger, more expensive filters.
What are the advantages of a sand filter?
Sand filters are popular because they're affordable, durable, easy to operate, and relatively inexpensive to maintain. They also have a long service life and use readily available replacement parts and filter media.
From the Author
Pool equipment can feel a little overwhelming at first, especially when you're staring at a pad full of pumps, filters, valves, and pipes that all seem to have a job to do.
I'm Cristian Shirilla, Marketing Manager at River Pools and co-owner of a fiberglass pool installation company in Virginia. I've spent years helping homeowners find clear, practical answers to questions about pool ownership and maintenance.
I put this guide together to explain how sand filters work, what they cost, and what it takes to maintain them over time. My hope is that by the end, you'll have a better understanding of this common filtration system and feel more comfortable managing it as part of your pool.
From the Manufacturer
At River Pools, we know that understanding your pool equipment is an important part of pool ownership. Whether you're researching your first pool or learning more about the equipment you already have, knowing how systems like sand filters work can make maintaining your pool feel a lot less intimidating.
If you're considering a fiberglass pool and want to learn more about the equipment, maintenance requirements, and ownership experience that come with it, the next step is connecting with a trusted independent installer in your area. They can help answer your questions, evaluate your backyard, and walk you through the options that may be the best fit for your needs.
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