(Click on a star to add your rating)

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

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.

**Click Here to View Inground Pool Pumps**

InyoPools Product Specialist

oyster56 - I don't see a motor replacement at 1.25 THP, but based on your information, you could probably use a motor with 1.1 or 1.0 THP. The 1.1 THP motor is a standard uprated motor, UST1102. The 1.0 THP motor is an Energy Efficient (EE) motor, UCT1102. The EE motor is $40 more but would save you 20% on operating costs. Also since these both are slightly smaller motors than your old one, you will have to buy a smaller impeller. And, for any motor replacements, you should buy a new shaft seal.Dennis R.Posted: 7/23/2013Reply

oyster56Posted: 7/23/2013Reply

InyoPools Product Specialist

Mike - Your pool holds about 10,000 gallons of water. A 1 1/2 HP pump should be sufficient to handle circulation for this size pool and your waterfalls.Dennis R.Posted: 7/18/2013Reply

MikePosted: 7/17/2013Reply

InyoPools Product Specialist

MM - For a head of 11' you would need a 1/2 HP Hayward Super Pump that would provide 55 GPM. This is overkill but this is the smallest pump we sell. For a head of 67' the charts show you would need a 1 HP Hayward Super II Pump (different class of pump) which provides 35 GPM. The next lower pump, 3/4 HP, is right on the edge of providing 19 GPM for 67' of head and the manufacturer recommends going up to the next level.Dennis R.Posted: 7/17/2013Reply

InyoPools Product Specialist

Bjtex - Yes, you could use a 1 1/2 HP pump but you're on the edge. You could hedge your choice a little by getting a 1 1/2 HP pump with a SF of 1.10 or 1.25 to get a slightly higher THP. THP = HP x SF. If you are concerned about operating cost and can afford the initial pump cost, you should look at buying an Energy Efficient (EE) pump or a 2 speed or variable speed pump.Dennis R.Posted: 7/16/2013Reply

MMPosted: 7/16/2013Reply

BjtexPosted: 7/14/2013Thanks

Reply

InyoPools Product Specialist

volts/amps/watts - A pool motor's volts/amps/watts are generally defined by the HP of the motor. With little exception, pool motors use either 115V or 230V. That is defined by the power available at the house. Amps (and Watts) are directly related to HP. The more HP a motor has, the more Amps/Watts it will use. Some EE motor are designed to be more energy efficient than their stand counterparts and might use 20% less Amps/ Watts for the same HP.Dennis R.Posted: 7/8/2013Reply

InyoPools Product Specialist

Glenn- Your main limitation is your pool's pipe size of 1 1/2". For your volume of water you could probably use a 2 THP pump but your piping should not use anything over 1 1/2 THP. Note that's real or Total HP [THP] which is the product of HP and Service Factor [SF] - see motor label. For example, a motor with a labeled HP of 1.5 and a SF of 1.4 has a real THP of 1.5 x 1.4 or 2.1 THP. If you have the option of changing out your piping for 2" or 2 1/2" pipes, you could use the larger pumps.Dennis R.Posted: 7/8/2013Reply

AnonymousPosted: 7/7/2013Reply

GlennPosted: 7/6/2013I have a 24x48 inground liner pool (50,000gallons). I have to run the pump 24/7 to keep clean. There is 2 stair returns, and 2 returns in shallow end for a total of 4 (2 lines leave pump and turn to 4). I then have 2 skimmers and one bottom drain. All the pipes are 1.5 inch. 500lb sand filter and a 1hp motor. What changes do I need to do so I don't have to run pump all day and night and keep a clean pool? Any advice would be super helpful! Thank you.

Reply

InyoPools Product Specialist

anna - This guide provides an estimate for a typical pool. With your pool's extra returns and drains, you could go with a 1 1/2 THP pump. A 2 THP pump is probably too big. However, if you have 2" piping in your suction and return lines, you could go with a 2 THP pump and if you find it's too much you could back it off by substituting a smaller impeller. Note make sure you are looking at real or Total Horse Power (THP) which is the product of HP and Service Factor (SF) when selecting a pump size. Some pumps labeled 2 HP can actually be 2.5 THP if the SF is 1.25.Dennis R.Posted: 7/2/2013Reply

annaPosted: 7/1/2013Reply

InyoPools Product Specialist

terry - For your size pool with a spa and water features and 2" piping, many people use a 2 HP pump.Dennis R.Posted: 6/29/2013Reply

terryPosted: 6/28/2013Reply

JJPosted: 6/22/2013Reply

InyoPools Product Specialist

Steelers7 - Sounds like going to a 1 1/2 HP pump is a good option. Your 600 # Sand filter will support the increased GPM flow and your pool is sized for it. Also, this size motor will support the addition of a new waterfall. When you move the pump and filter out 20', make sure that the wiring from the circuit breaker to the pump is at least 14 gauge for 230V or 12 gauge for 115V supply power. Consider buying an Energy Efficient (EE) pump for operational cost savings of 20%.Dennis R.Posted: 6/14/2013Reply

Steelers7Posted: 6/12/2013Reply

InyoPools Product Specialist

Jc - We generally recommend a pump with 1 1/2 Total Horse Power (THP) for a pool your size. THP is the product of HP shown on the motor label times its Service Factor (SF) printed on the label.Dennis R.Posted: 6/2/2013Reply

InyoPools Product Specialist

sendmiller - We would also recommend a 1 1/2 THP pump for your size pool. Be aware that when you are looking for a 1 1/2 HP pump you need to look at Total Horsepower (THP) which is the product of HP and Service Factor (SF). If you look at your motor label, your HP might read 1 HP and the SF might read 1.5. Your motor's THP would be 1 x 1.5 or 1.5 THP.Dennis R.Posted: 6/2/2013Reply

JcPosted: 6/2/2013Reply

sendmillerPosted: 6/1/2013Reply

InyoPools Product Specialist

Alleng - We recommend a 1 1/2 HP pump for an Above Ground pool holding 17,000 gallons of water.Dennis R.Posted: 5/29/2013Reply

AllengPosted: 5/27/2013Reply

InyoPools Product Specialist

Bart - We would recommend a 1 1/2 THP pump for your size pool. You have to look at Total HP (THP) when sizing a pump for your pool. THP is equal to HP x Service Factor (SF) as shown on your motor's label. Your old B129 has a THP of 1.95 which was probably larger than you needed. The Tristar EE pump is a good option. I would recommend the 1HP motor (THP 1.85). But a better option, if you can afford the initial cost, is the new Hayward Variable Speed (VS) Super Pump. It is rated at a maximum 1.5 HP. About half the size of the original VS pumps. The initial cost is higher but you can get that back in cheaper operating costs in the first year. And because they are sealed, they will last 2 to 3 times as long as a standard motor. See your guide on How to Save Money Using a Variable Speed Motor for more information.Dennis R.Posted: 5/23/2013Reply

BartPosted: 5/22/2013Reply

InyoPools Product Specialist

Frank - In-ground and above ground pool pumps are designed differently. Since an above ground pump is installed below the water level, it can rely on gravity to feed water into the pump. An in-ground pool pump is installed above the pool's water level and is designed to suck water from the pool to the pump.Dennis R.Posted: 2/24/2013Reply

FrankPosted: 2/22/2013Reply

InyoPools Product Specialist

JayinFL - I would go with a third option, the SP3207EE model - Total HP = 1.39 (HPxSF). This model would deliver the same Total HP as your previous motor. The SP2010EE has a Total HP of 1.85 which I think would be overkill for your setup.Dennis R.Posted: 2/11/2013Reply

JayinFLPosted: 2/11/2013Reply

InyoPools Product Specialist

m.fed67 - With your size pool and no water features or suction cleaner, I would stick with the single speed pump as you suggest.Dennis R.Posted: 2/11/2013Reply

m.fed67Posted: 2/9/2013Reply

InyoPools Product Specialist

ttiger - You have a large pool and if you have other water features, you may need your current size pump. I assume that the pump was sized to your pool. If you are trying to reduce costs, I would suggest looking at a 2-speed or a variable speed pump or motor. See our guide on variable speed motors for potential savings.Dennis R.Posted: 9/4/2012Reply

ttigerPosted: 9/3/2012Reply

InyoPools Product Specialist

watergirl - We will have to look up your impeller information in our files. Please give us a call.Dennis R.Posted: 7/3/2012Reply

watergirlPosted: 6/30/2012Reply

InyoPools Product Specialist

Trut,Dennis R.Posted: 6/23/2012I'm going to have to take another look at our calculations on this guide. Generally for your size pool, 19,000 gallons, we recommend a pump size of 1 to 1 1/2 HP.

Reply

InyoPools Product Specialist

Desperate - We would generally recommend a 1 1/2 HP pump for a 19-20,000 gal pool but before you change make sure you have followed the following. If your algae is really bad you may have to shock it twice. We recommend Zappit, http://www.inyopools.com/Products/22300006058112.htm. Also use a good algaecide with the shock treatment: http://www.inyopools.com/Products/22300006058112.htm and finally add Chlorine stabilizer to prevent the sun from depleting your chlorine - aka Cyanuric Acid: http://www.inyopools.com/Products/22300006058077.htm. See our Q&A section under Chemicals for more information.Dennis R.Posted: 6/22/2012Reply

TrutPosted: 6/21/2012Reply