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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.

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

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

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:

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:

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 the required gallons per minute (GPM)** 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 pool example**, the GPH required is 20,250 gallons / 8 hours or 2531 GPH.

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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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.

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***

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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RichPosted: 5/4/2022Reply

InyoPools Product Specialist

What is the model number of your current pump? The information provided is excellent, but calculating feet of head blind is not a good way to do things. So, we'll use your current pump as a baseline. Also, "moving the most water" you can is not always the best way to do things.Matt S.Posted: 5/11/2022 LatestReply

Cleveland WardrickPosted: 4/11/2022Reply

InyoPools Product Specialist

We don't carry any Jacuzzi 1.85 VS pool pump, so I am not sure which model you reference. Jacuzzi is a manufacturer that sells different lines of VS pumps, which would have varying flow rates. But it looks like you have all the information needed to look at the pump curve for the specific model.Matt S.Posted: 4/14/2022Reply

AnonymousPosted: 4/9/2022Reply

InyoPools Product Specialist

Yes, it should be enough based on the information provided.Matt S.Posted: 4/14/2022Reply

Lawrence SPosted: 3/25/2022Reply

InyoPools Product Specialist

The 1HP pump is undersized for a 40,000-gallon pool, but the 1.5" plumbing restricts you from going higher than a 1.5-1.65HP. 2HP pump would cause cavitation, which is terrible for your system. The flowrate boost produced by switching to a 1.65VS pump should give you a noticeable difference.Matt S.Posted: 3/28/2022Reply

AnonymousPosted: 10/12/2021Reply

InyoPools Product Specialist

No, but you can use an online gallon to liter calculator to use the formula, and then convert the totals back to metric.Matt S.Posted: 10/14/2021Reply

QDallasPosted: 10/4/2021Reply

InyoPools Product Specialist

You've done some excellent work there. You are correct; the 1.65 would be my preferred choice. Of course, you could always go with a 1.65 or even a 2.7 HP VS to give you the top-end flow rate if you ever have to do a chemical treatment or heavy cleaning. But if you are going with a single speed, the 1.65 would be my choice.Matt S.Posted: 10/5/2021Reply

Brian jandyPosted: 8/14/2021Reply

InyoPools Product Specialist

This sounds like a heater issue, not a pump issue. The hi-limit switch is telling the heater the water is too hot, not that there is a low flow. The most likely fix would be to replace the hi-limit sensor.Matt S.Posted: 8/17/2021Reply

PaulSPosted: 8/8/2021Reply

InyoPools Product Specialist

What is the model number of your pump housing? There is a wide range of pool pumps, I would need to know what you have to accurately compare the two.Matt S.Posted: 8/12/2021Reply

Paul SPosted: 8/12/2021Reply

InyoPools Product Specialist

That is the motor number. You need to look on the pump housing for the sticker, and not the motor case. You can see the difference between the two, here - Pool Parts 101: The Difference Between a Pump and a MotorMatt S.Posted: 8/13/2021Reply

Paul SPosted: 8/13/2021Reply

InyoPools Product Specialist

You should be able to use the TriStar 1.85 as a replacement for most pool pumps. The TriStar is Hayward's high-end residential pump, so it pushes more water than your standard Hayward Super II or Pentair WhisperFlo.Matt S.Posted: 8/17/2021Reply

BerniePosted: 7/19/2021Reply

InyoPools Product Specialist

Ok, you replaced a 2 HP pump with a smaller 1.5 HP; and now your heat pump is reading a PS code? If you reference the HeatPro manual it shows "PS" is referencing a low-pressure switch. I would take a look at the HeatPro Manual on page 18 for a list of solutions.Matt S.Posted: 7/20/2021Reply

DonPosted: 7/19/2021Reply

InyoPools Product Specialist

I think your calculation of feet of head is incorrect. A 1 HP pump would have trouble getting good flow through 90 feet of head, let alone 180 ft. You may be able to go up in HP, depending on the size of your filter. What is the model number of your filter?Matt S.Posted: 7/23/2021Reply

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