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Variable Speed Pool Pump Questions

Variable Speed Pool Pump Questions

This page looks at variable speed pool pumps to help pool owners to better understand their advantages and how to most effectively use one as your main filtration pump. You can also skip to one of these sections:

Concrete Pool Videos
Plaster Pool Videos
Vinyl Liner Pool Videos
Measuring Pool Liners
Pool Pumps Introduction
Pool Pump Troubleshooting
Variable Speed Pool Pumps
Pool Filter Videos
Salt Water Pool Videos
Swimming Pool Questions & Answers


Variable Speed Pool Pumps

How Much Money Can I Save With A Variable Speed Pool Pump?

Single speed pool pumps are similar to a car that only has two settings - "OFF and Full Throttle" - which is not very practical if you think about it. High speed electric motors all run at 3450 RPM and if you have a one speed pool pump this is what you have. Two speed pumps are also available which have the ability to run at 3450 and also half that value, 1725 RPM. A variable speed pump is like a dimmer switch for your pump motor which allows you to set the exact RPM value that meets your specific needs. Most single speed pumps far exceed the actual GPM filtration requirements for residential pools and this is where the variable speed pumps shine. The actual dollar value that you will save monthly will depend on a lot of factors specific to your pool, but on average you will realize between 40%-70% electrical savings monthly.

If you intend to stay at your current address for a period of a few years or more then the math says that you should buy a variable speed pump. The savings after 2 years of running (or four half seasons in cold climate areas) most variable speed pumps will have saved enough money to actually pay for themselves completely. If you can keep your pump running for 7 years, which is most manufacturers recommended life span for a pool pump these days, then you will actually save enough money to buy a new variable speed pump - twice. Variable speed pool pumps are the single greatest technological breakthrough that the industry has seen in 30 years.


Cost Comparison Between Single Speed & Variable Speed Pumps

This video is a must see for any person considering the costs of a variable speed pump versus a single speed pump. This complete breakdown of costs and flow rates including examples of real world system operating numbers is a comprehensive overview of how variable speed pumps work to save money while improving the quality and quantity of filtered water daily. Most pools base their filtration amount from the hours per day that their pump runs, however the total volume of filtered water is actually the metric that should be used to determine how much is enough.


In this long form breakdown of a filtration schedule for a swimming pool we are able to achieve an effective water filtration rate of 95% daily, while saving a total of $4300 in electricity over a projected 84 month service life. Many pumps can and will run longer than this so it is reasonable to use 84 months of operation for calculating your return on investment. As displayed in this video there is specific advantage to filtering water more slowly in that the efficiency losses to turbulence and friction are all but eliminated when water travels slowly and with laminar flow. Also electric motors experience a drastic reduction of power consumption when the motor RPM reduces even a small amount, and these two improvements combine to make variable speed pumps a clear cost saving investment for pool filtration systems.


4 Hour Single Speed Pump Filtration Cost Versus 24 Hours Variable Speed Pump

The most common argument against getting a variable speed pump is that the pool owner only runs their pump for a few hours every day. This video walks you through the cost comparison for a very lean four hour daily filtration schedule for a single speed pump and then compares this to a variable speed pump. As shown in the video even at this leanest four hour schedule the variable speed pump is able to match (and exceed) the filtration volumes daily, while using substantially less power over 24 hours than the single speed pump uses in only four hours of operation.


Single speed pumps were never an efficient choice and could be compared to cars with no throttle control...only full throttle. It is remarkably inefficient and home owners would never allow this level of poor efficiency in any other appliance they have in their home. Which is strange since pool pumps can easily be one of the largest, if not the single largest electrical draw appliance in your home. It was only for a lack of technology and an abundance of low cost energy that pool pumps were ever accepted as single speed. Now that we have the ability to control motor RPM we can utilize basic mathematical concepts of power consumption and energy efficiency. Laminar flow water moves with almost no resistance to flow. When laminar flow speeds up too much it will begin to generate turbulence as well as experience increasing forces that resist flow due to friction. Turn down an electric motor to reduce energy losses from friction and turbulence, and also benefit from a huge drop in power consumption while still retaining impressively high flow rates even at lower RPM operation.


What Is The best RPM For A Variable Speed Pump?

In asking what the best RPM for your variable speed pump is you are looking for the wrong information, or at least information that is not possible to give you accurately. This is because every pool system will have a unique resistance to flow due to the way your system is built, the size and type of materials used, location of your pump relative to the pool including the height of the pump in relation to the pool water level. Further to this you will have different filter types, sizes and current state of debris load. The RPM that produces the perfect amount of flow in my pool might not do anything for your pool at all. You must understand that while RPM numbers are easy to share, it is actually the flow rates for the water in your system that are actually important.


Speaking in general terms the best speed for a variable speed pump is the lowest speed that achieves a reasonable rate of water flowing through the filtration system. Pools still need short periods of time every day at higher RPM operation however the vast majority of the day the pump should be running on the lowest RPM that achieves flow in the 10 GPM to 20 GPM range. 20 GPM over 18 hours of operation would result in 21,600 gallons of filtration and would cost pennies since the RPM needed to hold 20 GPM is very low and low RPM operation uses very little electricity. Even a few hours at high speed operation would consume more electricity than 18 hours of low speed operation. For more information you can read this article about Variable speed pump operating schedules.


How To Program A Variable Speed Pump

It used to be with a single speed pump that you needed to turn it off for part of the day every day in order to save money on the electrical costs to run the pump. With a variable speed pump you experience the most savings by operating the pump 24 hours per day. If you turn off the pump for part of the day this no longer represents a potential for savings, it represents the lost potential for additional savings. Your total run time and RPM speeds should be based on the total filtration volume you need for your pool. This should be a minimum of three turnovers of your pool volume every 24 hours. Instead of turning off your pump for part of the day you would run the pump continuously but you could likely reduce the motor RPM for the majority of the 24 hour schedule. Long periods of time are low RPM operation are where you make your greatest savings with a variable speed pool pump.


The nature of pump RPM versus flow volume is such that a pump running at 100% RPM speed, 3450 RPM, might move 100 GPM of water. If you turned down the RPM by half the power consumption would drop by anywhere from 5x to 8x less power than required at full RPM. Some people assume this means the pool will not have adequate flow to function, however the fail to appreciate how well (efficiently) water travels at low speed. Laminar flowing water experiences very little resistance to flow. When you reduce a pump motor RPM the flow rate will drop in a linear fashion along with the RPM. If out example pump moved 100 GPM at full speed then it will probably move about 50 GPM when the RPM is reduced by half. It is the non-linear drop in power consumption which is both fascinating, as well as the basis behind why variable speed pumps are so much more cost effective to operate. Low and slow wins the race with variable speed pumps, so long as you also include some periods of time at higher speeds every day to allow for better circulation of the pool water and function of the pool skimmers.


500 - 3450 RPM Power & Flow Rate Test (1.5" pipes)

This test of a variable speed pump is being conducted with 1.5" plumbing lines to show the flow rate and power consumption. The Pentair Superflo variable speed pump used here is a 1.5 HP pump and the filter is a Hayward C150S cartridge filter with a total system dynamic head of around 35 feet of head resistance. While the flow and power consumption values shown here are accurate, they are only accurate on this exact system and every swimming pool is unique. The flow volume from 1000 RPM on this system will undoubtedly be different than the flow volume you would experience on your system at 1000 RPM. This is why it is so important that you get a flow meter to go with your variable speed pump.


In this example the flow ranged from 11 GPM at 500 RPM (at 63W) on the lowest end up to 82.5 GPM at 3450 RPM (2150W) at the highest speeds. When you look at these numbers you can clearly see that as the speeds increase the power consumption increases far more than the flow volume. 11 GPM for 63 Watts is a lot of flow when you consider that 82.5 GPM consumes 2150 Watts of power! These tests prove beyond any doubt or misunderstanding why variable speed pumps are so important if you want to improve the efficiency of the filtration system on your pool.


500 - 3450 RPM Power & Flow Rate Test (2" pipes)
In this variable speed pump test you will see the flow rates and power consumption for 500 RPM to maximum speed, 3450 RPM as operated through a 2" plumbing system. The pump is the same 1.5 HP model as the 1.5" pipe size test, as is the 150 sf cartridge filter. As you can see the flow rates for a given RPM value are higher for the larger pipe size system including the maximum flow rate potential that the system can achieve. This is just a bench test however and it is important to understand that every swimming pool is different and your flow rates and RPM values will be unique to only your pool. This is just one example.


Starting at 500 RPM in this test you can already see how the 2" pipes outperform the similar test done on the 1.5" pipes. At 500 RPM in this test the system is able to achieve 14 GPM versus the 11 GPM from the smaller pipe size. At 3450, maximum RPM, this 2" system was able to achieve 98 GPM which is over 15 GPM more than the 1.5" system test. From low RPM to high RPM a larger pipe size system will reward you with higher flow rates for similar power consumption. Over the lifetime of a pool system this small improvement actually becomes a very significant energy and cost savings and definitely something that should be considered when designing an efficient pool system.


For more information and videos testing power consumption and flow rates you can check out this article about How much power does a pool pump use?


Concrete Pool Videos
Plaster Pool Videos
Vinyl Liner Pool Videos
Measuring Pool Liners
Pool Pumps Introduction
Pool Pump Troubleshooting
Variable Speed Pool Pumps
Pool Filter Videos
Salt Water Pool Videos
Swimming Pool Questions & Answers