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Your first step is to determine the number of gallons of water in your pool. The formulas for calculating the gallons depend on the shape of your pool.

For a RECTANGULAR POOL:

Measure the length (ft), the width (ft) and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in a rectangular pool is: Gallons = Length x Width x Average Depth x 7.5.

For example (see picture): your pool is 30 ft long and 15 ft wide. The pool's shallow end is 4 ft and its deep end is 8 ft. So, the pool's average depth is 4 plus 8 = 12 divided by 2. This gives you 6 ft. The pool's capacity is 30 ft x 15 ft x 6 ft x 7.5 = 20,250 gallons. Go to Step 5.

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For a RECTANGULAR POOL:

Measure the length (ft), the width (ft) and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in a rectangular pool is: Gallons = Length x Width x Average Depth x 7.5.

For example (see picture): your pool is 30 ft long and 15 ft wide. The pool's shallow end is 4 ft and its deep end is 8 ft. So, the pool's average depth is 4 plus 8 = 12 divided by 2. This gives you 6 ft. The pool's capacity is 30 ft x 15 ft x 6 ft x 7.5 = 20,250 gallons. Go to Step 5.

For a ROUND SWIMMING POOL:

Determine the number of gallons of water in your round pool, measure the diameter of the pool and its average depth. The average depth is determined by adding the depth at the shallowest part to the depth at the deepest part and dividing by two.

The formula for calculating the total gallons in a round pool is: Gallons = Diameter x Diameter x Average Depth x 5.9.

For example (see picture): your pool is 25 ft in diameter, the pool's shallow end is 3 ft and its deep end is 7 ft. So the pool's average depth is 3 plus 7 = 10 divided by 2. This gives you 5 ft. The pool's capacity is 25 ft x 25 ft x 5 ft x 5.9 = 18,428 gallons. Go to Step 5.

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Determine the number of gallons of water in your round pool, measure the diameter of the pool and its average depth. The average depth is determined by adding the depth at the shallowest part to the depth at the deepest part and dividing by two.

The formula for calculating the total gallons in a round pool is: Gallons = Diameter x Diameter x Average Depth x 5.9.

For example (see picture): your pool is 25 ft in diameter, the pool's shallow end is 3 ft and its deep end is 7 ft. So the pool's average depth is 3 plus 7 = 10 divided by 2. This gives you 5 ft. The pool's capacity is 25 ft x 25 ft x 5 ft x 5.9 = 18,428 gallons. Go to Step 5.

For an OVAL SWIMMING POOL:

To determine the number of gallons of water in your oval pool, measure the longest diameter, the shortest diameter and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in an oval pool is: Gallons = Longest diameter x Shortest diameter x Average depth x 6.7.

For example (see picture): Your pool's longest diameter is 25 ft, shortest diameter is 15 ft and the pool's average depth is (3 + 7) / 2 = 5 ft. The pool's capacity is 25 x 15 x 5 x 6.7 = 12,563 gallons. Go to Step 5.

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To determine the number of gallons of water in your oval pool, measure the longest diameter, the shortest diameter and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in an oval pool is: Gallons = Longest diameter x Shortest diameter x Average depth x 6.7.

For example (see picture): Your pool's longest diameter is 25 ft, shortest diameter is 15 ft and the pool's average depth is (3 + 7) / 2 = 5 ft. The pool's capacity is 25 x 15 x 5 x 6.7 = 12,563 gallons. Go to Step 5.

For a KIDNEY-SHAPED SWIMMING POOL:

To determine the number of gallons of water in your kidney-shaped pool, measure the largest width, the smallest width and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in a kidney-shaped pool is: Gallons = (Longest width + Shortest width) x Length x Average depth x 3.38.

For example (see picture): Your pool's length is 25 ft, longest width is 15 ft, shortest width is 10 ft and the pool's average depth is (3 + 7) / 2 = 5 ft. The pool's capacity is (15 + 10) x 25 x 5 x 3.38 = 10,563 gallons.

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To determine the number of gallons of water in your kidney-shaped pool, measure the largest width, the smallest width and the average depth. The average depth is determined by adding the depth at the shallow end to the depth at the deep end and dividing by two.

The formula for calculating the total gallons in a kidney-shaped pool is: Gallons = (Longest width + Shortest width) x Length x Average depth x 3.38.

For example (see picture): Your pool's length is 25 ft, longest width is 15 ft, shortest width is 10 ft and the pool's average depth is (3 + 7) / 2 = 5 ft. The pool's capacity is (15 + 10) x 25 x 5 x 3.38 = 10,563 gallons.

Now that you have calculated the number of gallons in your swimming pool, you want to determine how many gallons per hour (GPH) you need to pump to clean all the water in your pool in eight hours. To come up with this flow rate, simply divide your calculated gallons by eight. For the RECTANGULAR swimming pool example the GPH required is 20,250 gallons / 8 hours or 2531 GPH.

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Most pool pump specifications are expressed in gallons per minute (GPM). So, to convert from GPH to GPM, divide your GPH by 60 minutes - 2531 GPH / 60 = 42.2 GPM.

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Having calculated your required GPM, you next have to figure out the average Feet of Head for your pool pump. Check out our blog on How to Calculate Feet of Head. PLEASE NOTE, WE ARE CURRENTLY REVIEWING OUR PROCEDURE FOR ESTIMATING FEET OF HEAD. CURRENT ESTIMATES ARE TOO HIGH.

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You now have the information required to select the size of your pool pump. Go to the description page of the style of pump you would like to purchase. Many pump manufacturers will provide a chart on this description page showing the HP required for your particular GPM and Foot 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 calculated above for a typical RECTANGULAR pool, we are looking for a pump that will handle 42GPM with a 47 Feet of Head. According to the chart for 50 Feet of Head (closest to 47'), we need a pump between 3/4 HP (31 GPM) and 1 HP (50 GPM). Since we always go for the higher GPM, we would select the 1 HP pump.

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The full performance page for the Hayward Super Pump can be found at this link, Hayward Super Pump. For the location of performance pages for other pump models, contact an Inyopools sales representative at 1-877-372-6038.

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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 encounters resistance at the filter. This will eventually burn out the pump motor and your filtration will also be compromised. We recommend selecting the filter so that it is oversized to be absolutely certain it can handle the flow coming from the pump. So, in this case, instead of getting a filter rated at exactly 42 GPM, you should select one that is a little higher – around 60 GPM would be fine.

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There are a couple of other considerations that should be mentioned in your selection of a pool pump. The above calculations are based on a basic pool configuration with no extra water features like: fountains, spas, waterfalls, solar heating, and in-floor cleaning systems. These features generally require higher GPM rates which equate to a higher HP pump. 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.

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DesperatePosted: 6/20/2012Reply

InyoPools Product Specialist

bmccormack - For your size pool I would lean towards the larger 1 HP pump.Dennis R.Posted: 6/20/2012Reply

bmccormackPosted: 6/20/2012Reply

InyoPools Product Specialist

Yes there is a difference in pump design between an in ground pool pump and an above ground pool pump. Because an above ground pool pumps is installed below the surface of the water, the water is fed into the pump with gravity. An in ground pool pump, on the other hand, is installed above the surface of the pool so is designed to suck water into the pool pump. You will need to get an in ground pool pump and for your size pool I would recommend getting a 1 1/2 HP pump.Dennis R.Posted: 6/16/2012Reply

AnonymousPosted: 6/15/2012Reply

InyoPools Product Specialist

atpool - If you have low flow your problem is more likely to be with the pump and suction side that the filter. If your impeller is sound and not clogged, check for leaks in the piping- especially at any unions and valves. Check for blockages in the piping. If you replace the motor, you might go to 1.5 for that size pool. With the new size motor you may need a larger impeller. Also you might consider also stepping up the filter one size to accommodate the larger motor.Dennis R.Posted: 6/3/2012Reply

InyoPools Product Specialist

VB - If you are looking for the most energy efficient Hayward motor, we would recommend getting a Hayward EcoStar Variable Speed pump. They cost more initially but you will recover your initial buy costs in less than a year with significantly reduced (80-90%) operational costs. And it gives you the flexibility to adjust your water flow rate to meet your current problems. See our How to Guide on variable speed pumps for more information.Dennis R.Posted: 6/3/2012Reply

atpoolPosted: 6/2/2012Reply

VBPosted: 6/1/2012Thank you so much for the article and information you provided.

-Vik

Reply

InyoPools Product Specialist

Jagajak - 2 HP sounds like overkill for a 10,000 gallon pool unless your spa adds 5000 gallons to it. Even if your total gallons is 15K you could easily get by with a 1 1/2 HP motor or convert to a smart pump for circulation.Dennis R.Posted: 5/25/2012Reply

JagajakPosted: 5/25/2012Reply

InyoPools Product Specialist

Poolman2 - Sounds like you could reduce your filtering time in half. I would try that and if your pool doesn't stay clean, raise filtering an hour.Dennis R.Posted: 5/22/2012Reply

Poolman2Posted: 5/22/2012Reply

InyoPools Product Specialist

tailgate - The typical TDH for most pools your size is 45 to 60 feet. 20 feet sounds way low. Does any of your suction piping run around the perimeter of your pool before going to the pump. Sounds like you have minimal suctions piping, but I would go for a 3/4 HP to be safe.Dennis R.Posted: 5/10/2012Reply

tailgatePosted: 5/8/2012Reply

InyoPools Product Specialist

NADB - The cost of a 2 HP pump on-line is $500-$600 depending on your pump model, so $700 installed doesn't sound that out of line. If you are trying to save money and since your pool is only 15,000 gallons you could replace your motor with a 1 HP or 1 1/2 HP motor - especially if you don't intend to use the Spa. Get a price on-line for both options and shop around for a couple of more quotes for peace of mind.Dennis R.Posted: 3/19/2012Reply

Not a Dumb BlondPosted: 3/17/2012Reply

InyoPools Product Specialist

Carpaul5 – Your pump’s total HP (THP) is a product of its HP times its service factor – “SF” on your pump motor label. If your motor’s HP is 2.0 and SF is 1.25, your pump motor is rated as 2.5 THP. If the SF is 1.0, the motor is rated as 2.0 THP. So if your old 2 HP motor has the same SF as your new motor, they are the same. 2-speed pumps run at full speed (3450 RPM) or half speed (1725 RPM). So you might run your filtration system at 1725 RPM for 10 hours and your suction cleaner at 3450 for 2 hours. A variable speed pumps can be programmed for up to 8 speeds with 8 different time slots at any speed between typically 800 – 3450 RPM - for example filtration at 1000 for 8 hours, cleaner at 2500 for 3 hours, spa at 3450 for 2 hours etc. Now the savings: A basic law of physics says if you reduce the RPM by one half from 3450 to 1725, you reduce energy cost to 12.5%. If it costs you $60 a month to run your single speed pump, it would cost you something like $15 a month running a 2-speed and maybe $10 a month with the variable speed. The variable speed is less because you can run the pump at a speed below half for a major portion of your time.Dennis R.Posted: 2/27/2012Reply

carpaul5Posted: 2/23/2012Also, please explain how variable speed and 2-speed pumps differ and how they achieve the energyy savings over a single speed. (I want to make sure my particular configuration and use patterns would produce savings) - Thanks

Reply

InyoPools Product Specialist

Carpaul5 - Roughly speaking, If your current pump is 1HP I would go to 1 1/2. If you are at 1 1/2 now and have an average size pool, I would stay at 1 1/2.Dennis R.Posted: 2/7/2012Reply

carpaul5Posted: 2/5/2012Thanks

Paul

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BobcatPosted: 1/2/2012Reply

InyoPools Product Specialist

We give a 5-7 day turn around for most of our pool products sold in June busy season. Pool Pumps typically ship out a little quicker.Dennis R.Posted: 6/6/2011Reply

charliePosted: 6/5/2011For my info, how long would it take to get a Hayward SP2607x10 shipped and received into MA??

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paulPosted: 5/23/2011Reply