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Pool Filters FAQs



Beach Ball How big of a filter do I need? [open]
If you’re unsure of what your pool’s volume is here’s a quick formula you can use:

Length x Width x Average Depth x Multiplier = Volume in Gallons
  • Multiplier for rectangular and square pools is 7.5
  • Multiplier for oval pools is 6.7
  • Multiplier for round pools is 5.9
Note: All measurements should be in feet, including the depth. For above ground pools, assume that the water depth is 6” less than the wall height, so if your pool is 48”, assume the depth is 3.5’, and for 52” pool, use 4’.

If math isn’t for you, take a look of the chart below featuring common pool sizes and how many gallons of water each size holds.

Swimming Pool Gallons Swimming Pool Gallons

For more help with calculating your pool size, visit our blog, How to Calculate the Number of Gallons in Your Pool.

If you can’t remember the HP of your pump and its flow rate, you should be able to find this information on the pump. If not, base your filter choice on the size of your pool. Swimming Pool Gallons
Beach Ball What would happen if I got a filter too small for my pool? [open]
The smaller the filter the longer it will take to clean and sanitize your pool. Not only will a small filter take a large amount of time to clean your pool it will also overwork your pump. Since the pump and filter work together as a team if they are not in tune then it can negatively impact your entire system. [Shop All Filters]
Beach Ball Is there a way to make my sand filter more effective? [open]
A traditional sand filter can only filter down to 20 microns, but that can be improved upon with the proper equipment. There are several additives for sand filters as well as replacement parts that would improve performance. These additives and replacements includes Luster Filter Media, Zeo-Clear Swimming Pool Sand Filter Alternative and Filter Glass. [Shop All Filter Supplies]
Beach Ball How do I clean my filter? [open]
For Sand Filters: To clean your sand filter you will need to start by backwashing with a backwash hose rolled completely out in order to carry the expelled water from your pool into the desired area. This process will typically take a few minutes.

You should be backwashing your filter when the pressure gauge rises over 8 to 10 psi over its starting point. Additionally, it’s recommended to backwash after heavy rains, treating algae and to help clear cloudy water.

For Cartridge Filters: You should clean your filter a few times over the course of the summer and can accomplish it with your garden hose and a basic attachment.

Spray your cartridge with a cleaner — such as Power Blue Cartridge and D.E. Swimming Pool Filter Cleaner — and let it sit for about 10 minutes. Then, you’ll use your hose and spray nozzle to spray each pleat, running down the length of the filter at an angle. Once you finish, you’ll want to flip the cartridge over and do it again. Make sure you do it at an angle to avoid pushing debris further into the filter.

There are numerous cleaners to clean your filter, just be sure to properly follow the instructions associated with each cleaner since some of them require the filter to soak overnight. We also sell several specialized hose attachments to make cleaning easier.

For more information on cleaning your cartridge, check out our blog, Cleaning Your Pool Cartridge Filter.

For D.E. Filters: It’s best to clean your D.E. filter every month or whenever the pressure gauge rises 8 to 10 psi over its starting point.

Start by backwashing your filter. Once complete, clean the grids within, shaking off the D.E. powder. You’ll also want to clean off the inside of the tank. After you reassemble the tank, add new D.E. powder. [Shop All Filters & Filter Supplies]
Beach Ball Why is D.E. powder harmful? [open]
If a large amount of Diatomaceous Earth is inhaled it can cause coughing, shortness of breath, skin irritation and eye irritation. D.E powder is a known carcinogen though it has only proven to be cancer-causing in mice when being inhaled long-term. [Shop D.E. Powder]

Swimming Pool Buyers Guide FILTERS

A filter system is one of the most important pieces of equipment for your pool. A filter works alongside your pump to filter and sanitize your pool water, keeping it free of debris, bacteria and algae.

It’s easy to know you want to get the best filter for you and your pool, picking that filter may not be as easy. With choosing between sand, cartridge and Diatomaceous Earth (D.E.) filters and accounting for the size of your pool and pump, there’s a lot to consider.
Beach Ball Sand Filters [open]
Sand filters are the most popular filtration method because of how affordable they are and how easy to use. Although they have the smallest filtration area, they are great for large pools since they rarely clog.

These filters use a tank filled with filter media sand to filter the water as it passes through. The sand has rough edges to pull out particles as small as 20 microns. Over time, the edges on this sand will erode and become smooth and become less effective, so it will need to be replaced every 5 to 7 years. The tank will outlast the sand.

Over the course of the pool season, you will want to backwash your filter as a way to clean it. [Shop All Sand Filters]
Beach Ball Cartridge Filters [open]
Cartridge filters are considered the most environmentally friendly method as they require less energy to run, need to run less frequently to filter all of your pool’s water and don’t require backwashing.

With a cartridge made of pleated polyester, they work by trapping contaminants in the pleats as water flows through. They are able to filter to as small as 10 microns, making them more effective than sand filters. They also tend to require little maintenance, but cartridges will need to be replaced every 2 to 3 years.

Over the course of the pool season, you’ll want to rinse your cartridge with water, periodically spraying it with a filter cleaner or soaking it in diluted muriatic acid or another cleaning solution. [Shop All Cartridge Filters]
Beach Ball Diatomaceous Earth (D.E.) Filters [open]
While the most expensive, D.E. filters are the most effective, filtering down to 5 microns, and can give pool water a polished look. It is also the most dangerous, as it can be harmful if inhaled.

D.E. filters work by pushing water through a tank filled with grids covered in a crumbly white powder. This powder is made of silica and the fossilized remains of small, aquatic organisms called diatoms.

During the course of the season, you’ll need to periodically clean your filter either by backwashing or bumping, which involves knocking some of the powder off the grids. After ever cleaning, you’ll need to add additional D.E. powder.

Before purchasing a D.E. filter, you’ll want to consider the regulations in your town or city. Some cities and towns have regulations in place about disposing of used D.E. If you’re unable to backwash your filter, you are allowed to empty the powder into a disposable container and throw it out that way. [Shop All D.E. Filters]
Beach Ball Pump and Pool Size [open]
As you decide which filter to purchase, you’ll wat to consider the size pump you have and its flow rate. Knowing the size of your pool and how many gallons it is may also be helpful. At, we rely on pool gallon size, pool surface area and pump HP to show how large the filter is.

Swimming Pool Gallons [Shop All Pumps]
More Questions?
If you still have some questions about filters or need help finding the right one, visit our blog, Demystifying Pool Filters: Sand vs. Cartridge vs. D.E., or call our in-house pool experts at 1-800-356-3025.