Pool filters need replacement when they stop cleaning water effectively, usually every 5 to 10 years depending on type and use

A pool filter removes debris, algae, and particles from your water. Over time, the filter media — whether sand, cartridge, or diatomaceous earth — becomes clogged and cannot trap new contaminants. You will notice cloudy water, reduced water flow through the pump, or a pressure gauge reading higher than normal. At that point, the filter has reached the end of its useful life and needs to be swapped out for a new one.

Replacement is not the same as cleaning. You can backwash a sand filter or rinse a cartridge to extend its life by weeks or months. But once the media no longer responds to cleaning, replacement is the only option. The cost and effort depend on which of the three main filter types you own.

Key Takeaways

  • Sand filters last 5 to 7 years before the sand needs replacement; cartridge filters last 3 to 5 years; diatomaceous earth filters last 2 to 3 years.
  • Sand filter replacement means draining the tank and shoveling out old sand, then refilling with new pool-grade sand — a job you can do yourself in a few hours.
  • Cartridge filters require buying a new cartridge element that slides into the existing tank; this is the easiest and cheapest replacement route.
  • Diatomaceous earth filters need the powder replaced after each backwash cycle, making them the most labor-intensive option over time.
  • You can buy replacement media at pool supply stores, big-box retailers, or online; prices range from under $50 for cartridges to $200 or more for sand and tank combinations.

Sand filter replacement: draining, removing old sand, and refilling

A sand filter is a large cylindrical or rectangular tank filled with graded pool sand. When the sand becomes too clogged to backwash clean, you must drain the tank, remove the old sand, and add new sand. This is a physical job but does not require special tools or skills.

First, turn off the pump and close the multiport valve. Open the drain plug at the bottom of the tank and let the water run out completely — this can take 30 minutes to an hour depending on tank size. Once empty, use a wet/dry shop vacuum to remove as much sand as possible from the bottom. Then shovel out the remaining sand into buckets or a wheelbarrow. A 24-inch tank holds roughly 400 pounds of sand; a 30-inch tank holds around 600 pounds. Wear gloves and a dust mask.

After the tank is empty, rinse the inside with a hose to remove sand dust. Add the new sand slowly while running water into the tank so the sand settles evenly and does not clump. Use only pool-grade sand, not play sand or construction sand — the grain size matters for filtration. Once full, close the drain plug, open the multiport valve, and run the pump for a few minutes to rinse the new sand before returning to normal operation.

Cartridge filter replacement: buying and installing a new cartridge element

A cartridge filter uses a pleated paper or synthetic element that traps particles as water passes through. The tank itself lasts many years, but the cartridge inside wears out and must be replaced. This is the simplest replacement job of the three types.

Turn off the pump and close the isolation valve if your system has one. Unbolt the top of the tank or unscrew the cartridge housing — the method depends on your model. Lift out the old cartridge and set it aside. Rinse the inside of the tank with a hose to remove any loose debris. Slide the new cartridge into place, making sure it seats fully at the bottom, then bolt or screw the housing back on. Open the isolation valve, turn the pump back on, and check for leaks around the seal.

Cartridge filters are sold by size and micron rating. Common sizes are 25 square feet, 40 square feet, and 60 square feet. Check your old cartridge or your filter manual to find the exact model number. Replacement cartridges cost between $40 and $150 depending on size and brand. You can buy them at pool supply stores, Walmart, Amazon, or Home Depot.

Diatomaceous earth filter replacement: adding powder after each backwash

A diatomaceous earth (DE) filter uses a fine powder coating on internal grids to trap particles. Unlike sand or cartridge filters, DE filters do not have a replaceable element — instead, you add new powder after each backwash cycle. Over time, this becomes the most expensive and labor-intensive option.

After you backwash a DE filter, the powder rinses away and you must add new powder to restore filtration. The amount depends on your filter size; a typical residential filter needs 2 to 4 pounds of powder per backwash. You add the powder through the skimmer while the pump is running, and it coats the grids inside the tank. A 10-pound bag costs $15 to $30 and may last only a few backwash cycles if you backwash frequently.

DE filters are efficient and produce very clear water, but the ongoing cost of powder adds up quickly. If you backwash once a week during swimming season, you could spend $200 to $400 per year on powder alone. Some pool owners switch to cartridge filters to avoid this expense.

How to know which filter type you have

Look at the top of your filter tank. A sand filter has a multiport valve with a handle that rotates through settings like "Filter," "Backwash," and "Rinse." A cartridge filter has a housing with bolts or a screw-on top that you can remove to access the cartridge inside. A DE filter also has a multiport valve but includes a powder feeder basket near the skimmer.

If you are unsure, check your pool manual or look at the tank itself — most manufacturers stamp the filter type and size on a label. You can also take a photo and show it to a staff member at a local pool supply store; they can identify it in seconds.

Where to buy replacement media and what to expect to pay

Pool-grade sand is available at pool supply stores, Home Depot, Lowes, and online retailers like Amazon. A 50-pound bag costs $10 to $20. You will need multiple bags depending on your tank size — a 24-inch tank needs 8 to 10 bags, a 30-inch tank needs 12 to 15 bags. Some stores offer delivery for large orders.

Cartridge elements are stocked at the same retailers. Prices vary by size and brand: a 25-square-foot cartridge runs $40 to $80, a 40-square-foot cartridge runs $60 to $120, and a 60-square-foot cartridge runs $100 to $150. Hayward, Pentair, and Intex are common brands. Buy the exact size and model number to avoid returns.

Diatomaceous earth powder is sold in 5-pound, 10-pound, and 25-pound bags at pool stores and online. A 10-pound bag costs $15 to $30. Food-grade DE is cheaper but not suitable for pools — always buy pool-grade DE, which is treated to prevent clumping.

Signs your filter is failing and needs replacement soon

Watch for these warning signs: water stays cloudy even after running the filter for 24 hours; the pressure gauge reads 8 to 10 PSI higher than normal; water flow from the return jets slows noticeably; or you backwash or clean the filter more than once a week and it still does not clear the water. Any of these means the filter media is at the end of its life.

Do not wait until the filter stops working entirely. A failing filter puts extra strain on the pump and can cause the motor to overheat. Replacing the media before complete failure saves you from a costly pump repair down the road.

Frequently Asked Questions

Can I replace a sand filter with a cartridge filter?

Yes, but it requires more than just swapping the tank. You need to check that your pump and plumbing connections match the new filter's inlet and outlet sizes. A pool professional can assess compatibility in one visit. Many homeowners do make this switch to reduce maintenance and cost.

How long does it take to replace a sand filter?

Draining, removing old sand, and refilling takes 2 to 4 hours for a typical residential tank. If you hire someone, labor costs range from $200 to $500 depending on your location and tank size. Doing it yourself saves the labor cost but requires physical effort.

What happens if I use the wrong type of sand?

Play sand or construction sand has inconsistent grain sizes and will not filter properly. Water will cloud quickly, and sand may escape into the pool. Always use pool-grade sand, which is washed and graded to specific sizes for filtration.

Do I need to drain the pool to replace a cartridge?

No. You only need to turn off the pump and close the isolation valve. The water stays in the pool while you replace the cartridge element inside the tank. This makes cartridge replacement much faster and easier than sand replacement.

How often should I replace my filter media?

Sand filters need replacement every 5 to 7 years; cartridge filters every 3 to 5 years; DE filters need powder added after each backwash. Frequency depends on how often you use the pool and how dirty your water gets. Regular cleaning extends the life of all three types.