What Size Pool Filter Do I Need: A Brief Guide

By: Auxilia Blog| On: January 2, 2023

Do you need help finding the right size pool filter for your property? Call Classic Marcite at (407) 521-6260.

“What size pool filter do I need?” You may ask this question when your old filter gives out or you’re setting up your new in-ground pool. It can be challenging to determine the correct size without considering some essential information.

Orlando’s residential pool resurfacing and renovations team explains what you need to know. Review the following information, then upgrade your pool with a high-performance filter from a trusted company near you.

Measuring Your Pool

A reliable pool filter reduces dust, bacteria, and other harmful elements in your pool water. In general, it’s a good idea to invest in a filter that is larger than what you think you will need. Bigger installations typically operate with better efficiency and last longer. 

However, before answering the question, “What size pool filter do I need?” you must measure your pool’s dimensions.

Determining Water Volume

Shop for a pool filter that can cycle through your pool’s volume within eight hours. A low-volume above-ground pool may only require a small system, like a cartridge filter. However, pools with over 25,000 gallons may need large sand filter systems to get the best results.

How do you measure your pool’s volume? Here are some simple equations you can use to find the solution:

  • Square/Rectangle Pool Designs: Measure the length of your pool and multiply it by its width. Multiply that number by the average depth of the pool, and multiply it again by 7.5 for your total volume. 
  • Oval Pool Designs: Multiply the diameter of the longest side of your pool by the diameter of the shortest side. Multiply that number by the average depth of the pool and multiply again by 6.7.
  • Kidney Pool Designs: Multiply the average length and width of the pool. Take that number and multiply it by the average depth of the pool. Finally, multiply the sum by 7.

If you want to avoid doing the math, a professional pool renovation team can do the calculations for you. 

Calculating Gallons Per Minute

Once you calculate your pool’s volume, you must determine how many gallons per minute (GPM) your new pump should filter to complete an eight-hour cycle. 

Suppose your pool contains 15,000 gallons of water. Divide 15,000 by 8 (the number of hours to complete a cycle). You should come up with 1,875 gallons per hour.

Then, divide 1,875 by 60 (the number of minutes in an hour), and you get 31.25 GPM.

Understanding Feet of Head

While the total GPM represents how many gallons per minute a filter can process, it’s not precise. Feet of head also impacts the maximum flow rates of these appliances.

Feet of head represents the total resistance to flow in a pool system and accounts for factors like:

  • Water height
  • Length of the filter pipes
  • Pump rate

Remember that the higher your pool’s feet of head, the lower the pump’s flow rate. 

Contractors can usually calculate your pool’s feet of head during installation. Standard residential pools are generally between 40 and 50 feet.

Size Considerations for Residential Pool Filters

Once you complete all the necessary calculations, you can begin shopping for a filter. Most types of filters come in four or five sizes. Now, you can answer the question, “What size pool filter do I need if I have a small pool?” confidently.

Pool size is one of the most important factors to consider when purchasing a new pool filter and pump. A few rules of thumb are:

  • Above-ground pools don’t usually require more than a small filter.
  • Medium-sized pumps are suitable for around 15,000 gallons of water.
  • Large filters are ideal for pools that exceed 20,000 gallons (such as commercial pools).

Buying larger pumps will always be a better solution than buying a pump that is too small. This way, you get clean water all season without needing to remove debris from your device every couple of weeks.

You don’t need to be exact when measuring your pool for a filter. However, having a close estimate of your volume and GPM requirements will help you choose a good system. If you have questions about which size pump or pool filter size you need, a professional home improvement company can help.

Choosing the Right Type of Pool Filter

Review each filter’s flow chart to see overall performance ratings. Most filters show how many GPM they can process corresponding to the pool’s feet of head. These charts may vary depending on which type of filter you choose.

Sand Filters

Professional pool technicians recommend purchasing 24-inch diameter tanks that hold around 600 pounds of sand if you own an in-ground pool of 15,000 gallons or less. Avoid going lower than that to get the most efficiency out of your filter. 

Pools above 15,000 gallons require 30-inch tanks or larger.

Cartridge Filters

You can usually purchase pool filters by square feet. If you own a 15,000-gallon pool, a 150- to 200-square-foot cartridge filter should suffice. Pools with more than 25,000 gallons of water require a 400-square-foot filter.

Diatomaceous Earth Filters

Diatomaceous earth filters (DE filters) are the highest-performing products on the market. Most homeowners will buy these pumps small for their in-ground pools. Sizing up to a 48-square-foot DE filter is an excellent way to avoid constant maintenance.

If you own a pool with 25,000 gallons of water or more, don’t use any DE filter under 60 square feet.

Let Classic Marcite Help You Get the Most Out of Your Pool

Are you ready to upgrade your pool with superior pumps, filters, and decking? At Classic Marcite, we have everything we need to deliver fast and reliable service. We proudly provide unmatched pool renovations with 100% customer satisfaction.

See how our pool resurfacing company in Orlando can elevate the comfort and beauty of your property.

Do you still wonder, “What size pool filter do I need?” Learn more with Classic Renovations by Classic Marcite in Orlando, FL. Schedule a consultation at (407) 521-6260.