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What Size Pump For Pool

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How Much Water Does Your Pool Hold

HowTo: Size a Pool Pump

The first step in determining the proper size pump for your pool is to calculate how much water it holds. The reason for this is that your pool pump should be able to turn over the water in about 8 hours. In other words, all the water in your pool should run through your pump in that time span. And that should happen once a day.

To determine how much water your pool holds, start by looking at the paperwork that came with your pool. If you cant find the number of gallons it holds, dont worry. With a little simple math, you can figure it out on your own.

Just follow these formulas, depending on your pools shape, or use our pool volume calculator:

For a rectangular pool: Length X Width X Average Depth X 7.48 = Total Pool Gallons

For a round pool: 3.14 x radius squared x average depth x 7.48

For an oval pool: 3.14 x ½ Length X ½ Width X Average Depth X 7.48 = Total Pool Gallons

To determine the average depth in your pool, which you will need for the above formulas, add the shallowest part of your pool and the deepest part of your pool and then divide the number by two.

Calculate Your Pool Volume

First up, you need to figure out how many gallons of water are in your swimming pool. This calculation differs based on pool shape but is pretty straightforward. Use our pool volume calculator below, and then well start calculating the minimum flow rate you need for your pump.

The first metric is the pool volume which will help you determine the minimum and maximum flow rates required.

Pool capacity and calculations differ with the pools size and shape. There is a rectangular, circular, oval, and irregular-shaped pool. Which one is yours?

If you want a straight forward method, use the pool volume calculator below:

If you want to do the calculations yourself, here are the formulas to help you determine how many gallons of water your pool holds.

Other Things To Consider

Aside from the volume of your pool water, there will be other concerns to worry about like heavy usage, environmental factors like leaves that may contaminate your pool, and other small things that may contribute to your pool water needing to get circulated more often. This is why we always recommend the Water TechniX Pump Dual ECO Variable speed pool pumps. ECO pumps allow you to let the pump speed to energy saver to keep your pool clean during minimal use, and set it to full/regular mode in times when your pool water needs more circulation. A win-win situation. Not only will you get your pool water circulated at all times, but youre saving money on electricity costs as well.

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Size Your Pool Filter Accordingly

As our pool water makes it through the line to the pump, it is passed to another restricting element known as the pool filter. Every filter has a maximum flow rate as well, and if you go over that flow rate your water will not be filtered properly. We have included a chart so you can size your pool filter properly.

How Much Pump Do I Need

How to Select the Best Pool Pump

If your pool volume is 15,000 gallons, then one turnover would be equal to 15,000 gallons. This turnover is required every 12 hours, or twice a day. Pumps, on the other hand, use a slightly different description of “gallons per minute” or GPM. Think of this a little like the miles per gallon quoted as gas mileage on your car. Our goal is to meet or exceed our minimum required turnover and to use the least amount of energy doing it.

Here is the problem: most pools are designed to sell, not to operate. It has become very popular to “sell on horsepower” or how powerful a swimming pool water pump is, not how efficiently it operates. Many pool builders routinely sell against their competition by quoting a “bigger” pump as a “free upgrade.” As a result, the vast majority of pools have pumps that are severely oversized. Water pumps of 1, 1.5, and 2 horsepower are very common — and for the average size pool, very oversized.

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What Size Pump Do I Need

Ideally, you want a pool pump that can cycle all of the water in your pool through the filtration system once every 12 hours. To figure this out, you need to know how many gallons of water are in your pool.

This is pretty easy to do with some simple math using the following formulas:

  • Rectangular Pools: Length x Width x Depth x 7.5 = gallons
  • Round Pools: Diameter x Diameter x Depth x 5.9 = gallons
  • Oval Pools: Width x Length x Depth x 6.7 = gallons

So, when considering some of the more popular sizes of above ground pools, a 24-foot round pool has roughly 13,593 gallons of water and a 15 x 30-foot oval pool has about 10,000 gallons. This means for a 24-foot round pool, you need a pump that circulates 27,186 gallons per day. For a 15 x 30-foot oval pool, the pump has to circulate 20,000 gallons a day.

Now, heres where it gets a little tricky. Some above ground pool pumps are specified in gallons per minute and not gallons per hour. So, youre not quite done with your calculation. To convert to gallons per minute, you have to divide the gallons per day by 24 hours and then by 60 minutes. In our examples, the 24-foot round pool, you need 27,186 gallons cycled per day. This is about 1,132 gallons per hour or 18.8 per minute.

The 15 x 30-foot oval pool is a little easier to figure out. You need a pump that circulated 20,000 gallons a day, or 833.3 gallons per hour, or about 14 gallons per minute.

Determine Your Desired Turnover Time

The first thing to determine is the desired turnover time, or in layman terms, how long it takes for the pool pump to cycle all of the swimming pools water completely. An ideal turnover time is 8-10 hours.

Use this formula to determine your turnover rate:

Pool Volume in Gallons ÷ Turnover Rate in Minutes = Flow Rate

For example: If a pool is 35,000 gallons and we want a turnover rate of 8 hours, our equation would look like this: 35,000 / 8 / 60 = 73 GPM

According to the table above, we need a pump with a 73 GPM rating in order to achieve an 8 hour turnover time. Even though we figured out how much water needs to be pumped, the water can only flow at the maximum rate if the plumbing is big enough to accommodate it.

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Where To Find Pool Pump Flow Rate

Were going to ignore horsepower and choose a pump using the pumps performance graph. After all, what the pool needs is not increased horsepower, but an increased flow rate.

Each manufacturer will publish a graph like this one below. The colored lines represent a model of pump and their respective performance. That is their flow in gallons per minute with different amounts of total dynamic head.

Heres how to read a pool pumps performance graph.

To work out the correct size pump, you need the idea flow rate, we worked this out earlier, and the total dynamic head . Remember for average inground pools use a TDH of 50-60 and for above-ground pools, use a TDH of 20-30.

Lets assume your TDH is 50, simply look at the axis that has TDH, find 50 and slide horizontally across the graph until you hit one of the pump lines .

Now, follow this vertically down and look at the flow on the horizontal axis. If the flow is about what you need, then the pump is suitable. Its ok for it to be a little larger or smaller but not too much. Find the pump closest to what you need.

In this example, if we needed a flow rate of 65GPM, using a TDH of 50, slide across the graph horizontally and check both of the colored lines. The green line pump only has a flow rate of about 46GPM so its too small. The purple/blue line has a flow rate of approx 70GPM perfect.

Constants And Terms Used:

How To: Size A Pool Pump

7.5 = Number of Gallons Present in a Cubic Footr = distance across the center of a circular pool divided by 2 = a constant used in calculating area or volume of a circle

Square or Rectangular Shaped Pools w/Uniform Depth

x x x 7.5 = volume

Square and Rectangular Pools w/Shallow and Deep Ends

Length x width x AVERAGE DEPTH x 7.5 = volume AVERAGE DEPTH = /2

Circular Pools w/uniform depth

x radius squared x AVERAGE DEPTH x 7.5 = volume

Circular Pool w/Deep and Shallow Ends

x radius squared x AVERAGE DEPTH x 7.5 = volume AVERAGE DEPTH = /2

Kidney or Irregular Pools

Divide your swimming pool into smaller regular shapes, then use the above formulas to calculate their volumes. Once you have the volumes of the smaller pieces, add them up.

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Size And Selection Of Swimming Pool Pumps

Youve come to the mountain top, seeking wisdom and truth, or the answer to a question that has plagued humanity for all timeWhat is the best pool pump?

The first thing you need to know is that not all horsepowers are equal. Every pump has different flow characteristics, and the flow rate will vary by manufacturer and model.

But the question cannot be answered without some other key insights, namely your Pool Type, Turnover Rate, Filter Design Flow Rate and estimated Resistance, in Feet of Head.

Best Pool Pump For Pool

Pools that contain 40,000 gallons of water and above are usually large. Such pools require a flow rate between 83 GPM and 120 GPM.

Based on our flow rate per pump size table above, a 1.5 or 2 hp pool pump should generate this flow rate.

Here is a top choice based on this specification:

This pool pump from black+decker is designed with a low speed option for effective filtration.

The pool pump is user-friendly due to an easy to use touch pad for speed settings and high performance.

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Calculate The Total Dynamic Head

Now that we have the flow rate , we need to calculate the TDH in metres to determine the performance of the pump needed to turn over the water. TDH refers to the total equivalent height that fluid will be pumped by taking into consideration any friction losses in the pipe. Essentially dynamic head is the measurement of resistance working against your pool pump as it pulls water from your basin and pushes it back to the pool. Most inground pools will be somewhere around 15 metres TDH. Above ground pools typically fall around 9 metres TDH.

For example:

Head Loss – Pipe = 3.80 + Head Loss – Valves & Fittings = 6.20 = 10 Total Dynamic Head

Now that you know the Total Dynamic Head and the flow rate , you can use this information to find the size of pump you will need to efficiently turn over your pool.

Calculate Flow Rate And Turnover

How to Find the Right Size Pool Pump

Flow rate is the number of gallons the pump moves per minute, and turnover is the minimum about of time to circulate all water through the filter.

Use this formula to determine your turnover rate:

Pool Volume in Gallons ÷ Turnover Rate in Minutes = Flow Rate

Example: If you have a 25,000-gallon pool, and you want the water to turn over once every eight hours:

25,000 ÷ 480 = 52 GPM

Your 25,000-gallon pool needs an output of 52 gallons per minute to circulate the water once every eight hours.

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How To Size A Pool Heat Pump

Trying to learn how to size a pool heat pump?

In this post, we show you how

If you landed on this page, then chances are youre thinking about installing a heat pump. From unmatched energy efficiency to the ability to heat your pool with, or without the sun there are countless benefits to heat pump pool heaters.

Of course, to get the most out of your heat pump, its important that choose one suited to the conditions youll be using it in. Doing so ensures that you get the most consistent and cost-effective performance out of your heater.

It needs to be the right size.

But dont worry, there are only a few simple things to consider beforehand. And in this post, we go everywhere everything you need to know to size a pool heat pump for your swimming pool.

So lets just jump right into it

Choose An Ideal Flow Rating For Your New Pump

After you have calculated the MINIMUM FLOW RATING required to meet the turnover requirements of the pool, and after you have calculated the MAXIMUM FLOW RATING based on the limitations of the filter and piping, you are ready to select the proper size pump.

Draw a simple chart like the one below. Mark the MINIMUM FLOW RATING and the MAXIMUM FLOW RATING. The space between the minimum and maximum flow rate is the ideal range.

If you have a pool with no attached spa, you can choose a pump on the lower side of the ideal range. It will be sufficient to properly filter the pool without wasting energy in the process. In that case, we would look for a pump in the 50 – 60 GPM range.

If you have a pool/spa combination, you need to consider the flow requirements of the spa jets. This will often push you towards a pump on the higher end of the acceptable scale. In that case, we would look for a pump in the 75 GPM range.

If you have a pool/spa combination, you might want to consider a 2 speed pump. It can run on low speed while it filters the pool, and then switch to high speed when using the spa.

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Calculate The Maximum Flow Rate

The maximum flow rate is the highest water flow your pool plumbing system, and other equipment can support. If you bought a pump with a higher GPM than your pool, you risk bursting the system and wasting your electricity.

If you bought an above-ground pool, the maximum flow rates would be in the documentation. The same applies to pool equipment.

But if you built the swimming pool from scratch or if these details arent available, here is how to estimate your systems maximum flow rate:

a) Plumbing

The best place to start is at the pool plumbing and work your way to the pool filter and other equipment you may have along with the pool filtration and circulation.

You want to make sure the pool pump you use doesnt blow out your system. And the maximum flow rate of the pool plumbing will depend on the pipe size used. Thats why its a must that the system be labeled clearly.

If the contractor forgot to label, make a call. You can also the following standard values used in pool plumbing.

Pipe Size
2.5 120

But remember, the plumbing system in your swimming pool might be different in size. Some pipes might be smaller or bigger than your samples. So, while estimating its maximum flow rate, take the smallest value you get. It will help you avoid the risk of damaging the system.

b) Pool Filter

Itd be best to stay under the filters maximum flow rate as going overboard can damage it. Below is a breakdown of the various pool filter flow rates:

Surface Area

Min And Max Flow Rate Range

Choosing The Correct Size Pump For Your Pool, Factors To Consider

Almost there! Now that we have the minimum and maximum flow rates for your pool setup, put them together to get to your flow rate range: one of the two main specs for determining the pool pump size you need.

So, lets say you have a 15,000 gallon inground pool. With two turnovers per day, your minimum flow rate comes to 20.8 GPM.

Lets also say that you have a 2.3 square foot sand filter and 1.5 plumbing . You have to take the lower of those two values to make sure you dont overwork any components of your pool, so your maximum flow rate comes to 43 GPM.

In this example, our flow rate range comes out to 20.8-43 GPM.

Lets figure out the last main spec you need for your pool pump: total dynamic head.

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Calculate Maximum Flow Rate

The size of your pools pipes determines the maximum flow rate.

Count the number of intake lines for your pool and refer to the common pipe sizes below:

  • For each 1.5-inch intake line, the maximum flow rate is 42 GPM.
  • For each 2-inch intake line, the maximum flow rate is 73 GPM.

Example: Two 1.5-inch intake lines = 84. The maximum flow rate is 84 GPM.

This number is important because your pool filter has a maximum flow rate, which is measured in GPM. The pool pump’s GPM rating should be below the pool filter’s maximum flow GPM rating.

If the pool’s turnover rate is higher than the filter’s maximum GPM, the filter is undersized and will not work properly. If the filter is undersized, it should be replaced, or the pump should be undersized to prevent damage to the filter.

I Have The Volume Now What How Do I Determine Which Pump Is For Me

Now that you have the volume, its just a matter of selecting the right pump with the right flow rate. The best way to explain that would be to do an example. Lets use the first pool that we calculated the volume for.

Pool Volume = 65,947.5

Now, as a rule of thumb, we would want all of the pool water to be circulated within 6-8 hours, so lets use 6 hours as a baseline.

Divide the pool volume by the number of hours that you would want the pump to be running, so that would be 65,947.5 divided by 6.

This would give you 10,991 which means your pump should be able to turn around this much water in 6 hours. Since most pumps here in Australia are rated for Liters per minute, lets divide that number by 60 to get how much water needs to be pumped per minute. So we have 10,991 divided by 60, which is 183.

To circulate all of the water in 6 hours, we would need to have a pump thats rated at least 183 liters per minute. The closest pump we can get to hitting that mark is the Water TechniX Pump Alpha 1.0hp. This pump can churn out 210 liters every minute. Remember, when choosing a pump, choose one thats closest the required number of liters per minute, rounding up. This would give your pump enough extra power to compensate for dirt, filters, piping and other factors that will ultimately affect the flow rate of your pump.

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