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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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LoriPosted: 5/7/2021Reply

InyoPools Product Specialist

If this is a new install, does the cascade waterfall manual list a required/optimal flow rate? If this is an old install and you are just replacing the pump, what is the model number of the old pump?Matt S.Posted: 5/13/2021Reply

JenniferPosted: 5/4/2021Reply

InyoPools Product Specialist

The 1.5 HP Hayward Super Pump should be well suited for a pole that size. I'd go ahead and install.Matt S.Posted: 5/13/2021Reply

JenniferPosted: 5/13/2021Reply

JonathanPosted: 3/24/2021Reply

InyoPools Product Specialist

What do you mean by a 2 pump motor? Do you mean the pool had two pumps? Regardless of the answer, I would need to know the pumps' make and model to get an idea of what might need to replace them. Does the pool have a spa, water features like laminar or deck jets, or does it have a solar heater?Matt S.Posted: 3/26/2021Reply

HeatherPosted: 3/1/2021Reply

InyoPools Product Specialist

What is the model number of your pump housing? Pump flow rates can vary widely depending on the pump model.Matt S.Posted: 3/1/2021Reply

HeatherPosted: 3/3/2021Reply

InyoPools Product Specialist

Is this an inground or above ground pool? Because the DYN is a Pentair Dynamo pump that is used mainly on above ground pools. I did a search for both of the model numbers you listed, and the models came up on our site: 140210 and 340106Matt S.Posted: 3/4/2021Reply

Heather BurkPosted: 3/5/2021Reply

InyoPools Product Specialist

You can go with the same sized sand filter (140210), but if you are on a budget and you are sticking with the same pump, you can use a 21-inch tank Triton II TR50 Filter Side Mount 21 Inch Tank - 140249.Matt S.Posted: 3/8/2021Reply

LeonardPosted: 1/13/2021Reply

InyoPools Product Specialist

That is essentially a small lake, that would require a commercial-style pump and filtering system. That is not something we can size with that basic of info. If this is a new install we would need to know an accurate feet of head, plumbing size, any local codes that may affect the type of pump install. If you are replacing a pump, you can go with the same model and HP if you have that information.Matt S.Posted: 1/13/2021Reply

ChrisPosted: 9/14/2020Reply

InyoPools Product Specialist

I would not match a 2.5 horsepower pump with a 1.5" port multiport valve; guaranteed pressure issues.Matt S.Posted: 10/22/2020Reply

ChrisPosted: 10/22/2020Reply

lee r. swidlerPosted: 7/31/2020Reply

InyoPools Product Specialist

The Pentair IntelliFlo VF Variable Speed Pump - 011012 would be the ideal pump for your install. Because that is a very specific and relatively l low flowrate, a variable speed would be a must. The VF has an advantage over all the other variable speed pumps because it allows you to set your motor's speed based on desired gallons per minute instead of RPMs.Matt S.Posted: 9/1/2020Reply

JessicaPosted: 6/28/2020Reply

InyoPools Product Specialist

How do you know this is an issue with the pool pump and not an issue with your system? How to Correct Low Water Pressure in Your Pool SystemMatt S.Posted: 9/23/2020Reply

JessicaPosted: 6/28/2020Reply

InyoPools Product Specialist

Has the pump always struggled with low flow, or is this recent issue? If it is a recent occurrence, I will try troubleshooting the pump and plumbing using this guide - How to Correct Low Water Pressure in Your Pool System. It is a heck of a lot cheaper than a whole new pump.If this flow issue has been constant, I can try to find a suitable upgrade if you can provide me the model number of your pump.Matt S.Posted: 8/26/2020Reply

AnonymousPosted: 5/12/2020Reply

InyoPools Product Specialist

For a 35k gallon pool, I suggest using the Pentair IntelliFlo VF Variable Speed Pump - 011012 and the Pentair Filter - TA-100D (30-1/2") Tagelus W/ Valve - 145240Matt S.Posted: 11/10/2020Reply

Tom GPosted: 4/5/2020Reply

InyoPools Product Specialist

Is this a commercial or residential installation?Matt S.Posted: 4/7/2020Reply

Thomas GallagherPosted: 4/7/2020Reply

InyoPools Product Specialist

That would probably fall under commercial, which has different local ordinances and codes that vary depending on the area. You'd do best to contact a local contractor or inspector to have them guide you.Matt S.Posted: 4/7/2020Reply

AnonymousPosted: 3/30/2020Reply

InyoPools Product Specialist

The addition of the filter shouldn't have changed the flowrate of the system. it may have affected the PSI reading on your filter, but flow shouldn't be an issue. PSI does not necessarily equal the flow rate. The larger filter allows the water to sift through quicker, keeping PSI lower but the flowrate should stay unaffected; if not increase Take a look at this article: How Do I Correct Low Water Pressure?; for an idea of why you may have lower flow.Matt S.Posted: 3/31/2020Reply

BusterPosted: 12/13/2019Reply

MaryPosted: 12/6/2019Reply

InyoPools Product Specialist

You may install another Waterway SMF 1 HP Max Rate Single Speed Pump or you can use a different model like the Pureline Prime 1HP or Prime 1.65 VSMatt S.Posted: 12/9/2019Reply

AnwarPosted: 8/28/2019Reply

InyoPools Product Specialist

A 1/2 or 3/4 HP pump would be sufficient for your pool.Robert M.Posted: 9/4/2019Reply

DavidBPosted: 9/9/2019Reply

AnonymousPosted: 8/13/2019Reply

InyoPools Product Specialist

Because you have an above ground pool, this guide would be more helpful: How To Select Above Ground Pool PumpsFor a 24 ft round pool, a 1 or 1.5 horsepower pump would be sufficient.Matt S.Posted: 8/13/2019Reply