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How To Size a Pool Filter

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Before you can select the correct pool filter for your pool, you must first select the correct pump for your pool. Your pool filter must be matched to your pool pump. If the filter is too small relative to the pump. the pump will generate more water pressure in the filter than the filter is able to handle. This imbalance will quickly break down the filtering material of the filter which will greatly diminish the effectiveness of the filter. In more extreme cases, the high-pressure build-up may cause cracks in the filter tank causing it to explode. This guide covers how you should size your pool filter correctly.

Click Here to View Available Pool Filters

Related Article - How To Size an Abo



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Step 1

Pool Size - We suggest having a pump and filter that can cycle through your pool's volume within 8 hours. Depending on filtering and water chemistry demands, you may run the pump longer or shorter, but 8 hours is a good baseline mark.

To calculate your pool's volume in gallons, use the formula listed in this step's image. The formulas are listed according to pool shape. For example, if you have an L-shape, divide your pool into two rectangles, calculate their volume then combine the sums.

See our guide on How to Size a Pool Pump for Your In-Ground Pool for the formulas required to size your pool. For this guide, we will assume a typical in-ground pool size of 20,000 gallons.

Related Article - How To Size an Above Ground Pool Pump and Filter System

Step 2

Determine Required Gallons Per Minute (GPM) - After you have the number of gallons in your pool (20,000 gallons for this example), you will have to calculate the GPM required to filter 20,000 gallons in 8 hours.

To calculate this flow rate, first, divide your calculated gallons by 8 Gallons Per Hour (GPH). Then divide that number by 60 to get Gallons Per Minute (GPM). For our example of 20,000 gallons that's: 20,000 / 8 hours or 2,500 GPH divided by 60 mins/hour or 42 GPM.

Step 3

Calculate the Pool's Feet of Head (Feet of Water) - The pump's actual flow rate is determined by two factors, the horsepower rating the amount of pressure needed for the pump to prime itself. This resisting force, also called the Feet of Head, accounts for factors including pipe size, length of pipe, number of turns (elbows,) and rise in height the water has to overcome to reach the pump.

As Head increases, your pools actual GPM will decrease. Calculation of Head can be involved and is generally done during the initial installation of the pool. For a rough estimate, average the suction lines' lengths between the pool and the pump. Most basic in-ground pools have a Head of 40' to 50'.

We will assume 45' for this example.

Related Article - How To Size an Above Ground Pool Pump and Filter System

Step 4

Determine Pump Size - Now that you have determined your pool's required GPM and its Feet of Head, we can select the pump.

Go to the description page for your pool pump of choice. The pump's description should include its flow chart. A pump's flow chart lets you see the pump's estimated flow rate according to the specific horsepower and your plumbing's Feet of Head.

For example, say you wanted the popular Hayward Super Pump. An abbreviated version of the Hayward Super Pump Performance Page is shown at the left. Based on the data above, we are looking for a pump to handle 42 GPM with 45 Feet of Head. According to the chart for 50 Feet of Head (closest above to 45'), we need a pump between 3/4 HP (31 GPM) and 1 HP (50 GPM). Since we always go to the higher GPM, we would select the 1 HP pump.

Step 5

Determine Filter Size - The size of your pool filter is directly related to the pool pump you have selected. If your pool filter is too small for the pump, there will be additional strain on the pump motor as it tries to push water through and meets resistance at the filter. This will eventually burn out the pump motor, and your filtration will also be compromised.

We recommend over-sizing the filter to be absolutely confident it can handle the flow coming from the pump. So, in this case, instead of getting a filter rated at precisely 42 GPM, you should select one that is a little higher – around 60 GPM would be fine.

Click Here to View Available Pool Filters

Step 6

Other Considerations - A couple of other considerations should be mentioned in your selection of a pool pump and filter. The above calculations are based on a basic pool configuration with no extra water features: fountains, spas, waterfalls, solar heating, and in-floor cleaning systems. The features generally require higher GPM rates which equates to higher HP pumps/filters.

Also if your pool requires greater than 60 GPM you may need at least 2" diameter suction pipes. Suction pipes of 1 1/2" have a physical limit of 60 GPM. 2" pipes can handle up to 100 GPM.

Related Article - PVC Pool Pipe Dimensions

Step 7

Determining AG Pool Filter Size - The size of your system is mostly determined on the size of your above ground pool. The gallons found inside your pool will give you the horsepower needed for your pump. A simple rule to follow is you should be able to clear all of the gallons of your pool in an 8 hour period of time. You can use the following as a guideline.

• Above Ground Pool up to 24 Ft. Round = 1 HP pump
• Above Ground Pool over 24 Ft. Round = 1 ½ HP pump

Related Article - How To Size an Above Ground Pool Pump and Filter System
 

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(201 to 240 of 244)

 Posted: 3/7/2018 

Anonymous - Yes, you can use a C3030 cartridge filter with a 1 HP above ground pump. It is much larger than you need, but there is no limit to the upper size of a filter. You just won't have to clean it as frequently.
 Reply

Anonymous  Posted: 3/6/2018 

Can I put a C3030 hayward cartrige filter with an aboveground pool with a 1 hp pump?
 Reply

 Posted: 2/20/2018 

Drodn - Your pool contains about 16,875 gallons of water. For this size pool, I would recommend a 1.5 Hp pump like the PureLine Prime Pool Pump and a Hayward 27" Sand Filter with Top Mount Valve.
 Reply

 Posted: 2/18/2018 

I have a 15' X 30' fiberglass pool. The depth runs from 3.5' to 6' so I assume average depth at 5' to be conservative. Would a 1.5 hp pump and a 21" sand filter be the correct size for my pool? Thank you.
 Reply

 Posted: 1/16/2018 

Hi, I have a 22X52 Colman above ground pool and trying to determine what size sand filter. Thanks !
 Reply

 Posted: 11/13/2017 

Joe - A Pentair 1 1/2 hp VS pump would be a good choice for your size pool with the roof mounted solar panels. You didn't say why you hate your current filter other than having to clean it twice a week. If your want to switch to a sand filter, I would suggest something like a Hayward Sand Filter with Top Mount Valve 30 Inch Tank - S310T2.
 Reply

 Posted: 11/13/2017 

Scott- You can never have a filter that is too big for the pump. Many dealers even recommend upsizing the filter by 25% so there is no chance of the pump blowing out the filter. A larger filter just means that it will last longer between cleanings.
 Reply

 Posted: 11/12/2017 

I am looking to change out my pump and filter for my 15000 gal pool. I have 6 solar panels on my roof 10 to 12 feet above the pump and 2 little water sprays at the pool. I currently have a 1hp Starite single speed pump and a 150 Starite filter. I am cleaning this filter twice a week and hate it. Would like to know if a Pentair 1 1/2 hp VS pump would be sufficient and what size filter would I need. Piping head without solar is approx. 40 to 50 ft.
 Reply

 Posted: 11/4/2017 

I have a dayton 1 1/2 HP pump grainger #5PXC5A thats rated at 10ft/77, 40ft/51.7. I need a new filter and have been offered less than 6 months old at a very good price but I'm afraid its too much filter for the pump. It's a Hayward Stay Clear model CL1200, can you tell me if it will work?
 Reply

InyoPools Product Specialist  Posted: 9/28/2017 

Anonymous (3600 gal pool) - Your cartridge in your filter may be clogged with oils and chemicals that are difficult to wash out of the folds. If you haven't changed your cartridge this year, you might buy a new one. If you want to switch to a sand filter, look at the next size up, 35 GPM. Your current filter is 25 GPM (1500 GPH).
 Reply

Anonymous  Posted: 9/26/2017 

Hello, I have a roughly 3600 gallon frame pool. It is running a 1500GPH filter cartridge pump (Type c filter). We have fought with cloudy water and chemistry all summer, mainly chlorine, so we added a SWG. It was great for a couple weeks, now cloudy again. All numbers within range. Is our filter too small? I'm cleaning it every other day! Could a sand filter with higher GPH help?
 Reply

InyoPools Product Specialist  Posted: 9/25/2017 

maurice - I'd recommend a sand filter like Hayward's Sand Filter w/ Top Mount Valve 27 Inch Tank 2" Valve - S270T2 for your size pool.
 Reply

 Posted: 9/23/2017 

Hi, I have a 15000-18000 gal pool. I am trying to replace my cartrige filter with a sand on. what size do I need? (1.5hp pump. thx
 Reply

InyoPools Product Specialist  Posted: 9/7/2017 

mike - See our article on "Pool Filter Information" for a description of the three most common filter types.
 Reply

 Posted: 9/5/2017 

Daughter purchased new home with above ground oval 20,000 gal pool. We know nothing about pools I have down loaded you book. thanks. Q: which is better sand or cart filter any other type?? Mike
 Reply

InyoPools Product Specialist  Posted: 9/4/2017 

Jeff - We would recommend the Hayward S210T Filter w/ 1.5 HP Matrix Pump which is the set I think you are looking at. The S210T sand filter takes 200 lbs. of sand.
 Reply

 Posted: 9/2/2017 

We have a 52" 30' round above ground. We need a pump and filter combo. I am looking at the Hayward 21" with the 1.5 hp motor. I am planning on getting it online and was wanting to be sure. Btw, how much sand is in this filter?
 Reply

InyoPools Product Specialist  Posted: 8/25/2017 

hol - For your size pool, I would recommend a Hayward VL Series Sand Filter System, but I do not know how it will integrate with your skimmer filtration system.
 Reply

 Posted: 8/22/2017 

We have a 16x32 above ground. Needing new pump and filter system
We've always gone with sand filters so would like to stick with that. We have a double filtration system through skimmer and at the base of the pool. What size pump/filter is recommended?
 Reply

InyoPools Product Specialist  Posted: 8/22/2017 

Frank b - A 1 1/2 HP pump with a 19" filter is generally what we recommend for an above ground pool larger than 24'. However, if you are having trouble keeping your pool clear, you might go to a 22" sand filter.
 Reply

 Posted: 8/21/2017 

Gotta 33' x 52" with a 19" sand filter and 1-1/2hp pump. Seems small to me what do you think?
 Reply

InyoPools Product Specialist  Posted: 8/7/2017 

Rob - Since you have 1 1/2" pipe, I wouldn't go over 1 1/2 Hp on the pump. See Hayward 1 1/2 Hp Super Pump, SP2610X15 as an example. With that size pump, I'd recommend something like the Hayward Star Clear Plus 175 Sq Ft. Cartridge filter - C17502 or the Hayward Sand Filter with Top Mount Valve 27 Inch Tank - S270T.
 Reply

InyoPools Product Specialist  Posted: 8/7/2017 

Hope - For your size motor, I would recommend a Hayward Sand Filter W/Top Mount Valve 20" Tank. They are currently on sale.
 Reply

 Posted: 8/4/2017 

I have a 13000 inground pool, a 3/4 hp hayward pump and a s200 (24" top) sand filter. I would like to change out the filter. What size do I need?
 Reply

 Posted: 8/3/2017 

I have a 40,000 gallon in ground pool with 50 ft head 1-1/2" pipe. It has an old sand filter and 1hp motor that I'd like to change. What size should I use if I go with a new sand filter and pump? What would I use if I went with a cartridge filter and pump? Thank you.
 Reply

InyoPools Product Specialist  Posted: 8/1/2017 

John Smith - You are working this backwards. The size of a pump depends on your pool size and construction. Then your select a filter to match the GPM of the pump. However, a C1200 is frequently used with a 1 hp to 1 1/2 hp pump.
 Reply

 Posted: 7/31/2017 

I have a Hayward c1200 filter what size pump do I need to run with it .what would be the biggest one u can use???
 Reply

InyoPools Product Specialist  Posted: 7/17/2017 

Karen - Your friend's 27' pool contains a little under 17,000 gallons. For that size pool, we would recommend a pump/filter set with a 1 1/2 HP pump like Waterway's Carefree 19" Sand Filter & 1.5 HP 1Spd Pump.
 Reply

 Posted: 7/13/2017 

My friend has a 27 foot round above ground pool 52 inch deep. What size pump and filter would you recommend?? Thanks
 Reply

InyoPools Product Specialist  Posted: 7/10/2017 

DisneyHeart - A 1.5 HP pump and 150 sq ft filter like the Pentair 1.5 HP OptiFlo Pump 2 Speed Twist Lock Cord W/ 150 Sq. Ft. Clean & Clear Cartridge Filter, would work fine.
 Reply

 Posted: 7/9/2017 

We just purchased a 54x24 above ground pool. Would a 150sq foot, 1.5hp, 2speed pump/filtration system be big enough?? Or do we need the 190sq foot. We want the cartridge type. THANKS!!!!!!
 Reply

InyoPools Product Specialist  Posted: 6/26/2017 

Anonymous (ec40ac) - A filter should be able to handle about 25% more GPM water flow than the system's pump. The EC40AC filter is designed for 40 GPM. 1 HP pumps can generate up to 50-70 GPM, so you will need a larger filter.
 Reply

Anonymous  Posted: 6/23/2017 

I have a 27'x 52" above ground round pool. Currently using a Hayward ec40ac 1hp de filter. Is this adequate?
 Reply

InyoPools Product Specialist  Posted: 6/20/2017 

Anonymous (filter size) - The size of your filter really depends on the size of your pump. You want something about 25% larger than the average GPM of your pump. Assuming you have a 2 or 2.5 HP pump, I would recommend a filter with a 400-450 Filtration Area and a Flow Rate of 150 GPM.
 Reply

Anonymous  Posted: 6/19/2017 

I have a 30,000 gallon in ground pool with and average depth of 5.5'
What size cartridge filter do I need?
 Reply

InyoPools Product Specialist  Posted: 6/17/2017 

James - Your C1200 Star Clean Plus Cartridge Filter is a good match for your 1 1/2 HP Super Pump. The typical water flow for a 1 1/2 HP Super Pump is 70-80 GPM. The C1200 is designed to handle up to 120 GPM.
 Reply

 Posted: 6/16/2017 

I have a hayward 1 1/2 super pump with a hayward c1200 star clear plus hooked to a hayward heater. This is all to a roughly 15000-17000 gallon pool and seperate spa. Is this to small of a filter
 Reply

InyoPools Product Specialist  Posted: 6/9/2017 

Fritz - Assuming your current DE filter is something like a Hayward Pro Grid DE Filter 48 Sq Ft with a designed flow rate of 96 GPM and your current pump is 1 1/2 HP uprated, I'd recommend something like the Hayward Star Clear Plus 120 Sq Ft. Filter 1.5" Ports. If you have a 2 HP uprated pump, I'd recommend the next larger filter. We recommend getting a filter with a GPM capacity that is 25% larger than the pump's capacity.
 Reply

 Posted: 6/6/2017 

I have a 16'x32'pool with an average depth of 6'
The pool has an old DE filter that needs replacing.
I want to change over to a cartridge filter, what size would I need. Currently it's a 48sq ft
 Reply

InyoPools Product Specialist  Posted: 6/5/2017 

Kevin - A Pentair CCP430 filter is much larger than you need for a 17,000-gallon pool. With a 150 GPM or 9000 GPH rating it could turn over your pool in two hours. Most people try to turn their pool water over 1-2 times a day in 8 hours. I'd recommend going with a CCP320. Dealers usually recommend having a filter whose capacity is at least 25% greater than the normal GPM of the pump. To turn your pool over 2 times a day in an eight-hour period, you would need a GPM of 71 GPM (17,000 x 2 = 34,000 / 8 = 4,250 GPH / 60 = 71 GPM). I'd recommend the Pentair Whisperflo Pump 1 1/2 HP Uprated motor- WF-26 to deliver that GPM. A CCP320 filter with a 120 GPM capacity your gives you an operating buffer of 69% (120/71). You can always have a filter larger than you need. It can't have a GPM smaller that what the pump generates.
 Reply