How Many Hours Should You Run Your Pool Pump?
"How many hours should I run my pool pump?" sounds like such a straight forward question SURELY the answer must be straight forward also. Right Swimming Pool Steve? Right? Steve? Helloooooo?
Okay I am going to answer your question here but I want you to listen up and pay attention. I am going to tell you how it is. This is not a discussion about how much you should filter your pool water. These are known figures. DO NOT tell me about your neighbor Bob who always has perfect pool water and he only runs his pump for one hour ever second statutory holiday. You are wrong. Bob does not have perfect water. Anecdotal evidence about pool water clarity is not relevant to this discussion. Let me explain why anecdotal evidence is not useful. It rained yesterday. I could go and drink out of a puddle in the street in front of my house. I could rub it in my eyes and ears and you know what? Probably nothing happens. Does that mean drinking puddle water and rubbing it in your orifices is safe? Can we please all just agree that it would not be safe to do that? If everyone just started drinking out of puddles then the rates of illness, infection and even death from puddle water would become a nationally tracked statistic. There are standards for water filtration established by scientists and chemists, so we are fortunate enough that we do not need to guess about how much water you should filter.
You need to filter ALL of your water EVERY DAY
That seems easy enough, right? But in saying this we have changed the question. The question is no longer how many hours do I need to run my pool pump, but instead how much water do I need to filter in my pool? All of it. You need to filter all of the water in your pool. Every day.
Swimming Pool Steve, I understand now. I need to filter all of my water, everyday. Roger that. Sooooo how many hours per day do I need to run my pump to filter all of my water, please?
You can not measure water volume in hours per day. These are not compatible units of measurement. This is the giant, red, flashing beacon that is the missing link between the question you are asking and actually getting the correct answer that you need. If anyone actually tells you a number about how many hours you should run your pump, they have done you a disservice and have not calculated anything about your unique pool. This is a hugely important takeaway. All pools are different. Every last one will have different system pressures, restriction to flow, unique status of filter in a given moment...not to mention that the filter you have, the type of media, the size of the filter all are incredibly important considerations when asking how many hours to run your pump. It is not possible to make an informred decision on pump run time without first knowing some important information:
Pool Volume - If you don't know the volume of your pool then how could you possibly make an informed decision about how many hours per day your pump needs to be running? Your pool volume is approximated by multiplying the length x width x average depth, all in feet. Multiply this by 7.5 and that is how may gallons are in your pool. You need to "turnover" the volume of your pool either three times or four times every 24 hours, depending on whether you feel 95% is good enough, or if you would prefer 98% as your final number out of a total of 100%. If your goal is to filter all of your water every day then I think we can agree that 95% and 98% are both very strong scores. Would you feel the same way about 86% or even 63% or less? Each time you pump the volume of your pool through the filter this is called a turnover. It takes more than one turnover to filter all of your pool water, because the water does not line up in an orderly fashion to be filtered. Your first turnover nets you 63% of all of the water in your pool, the second turnover gets you up to 86%. The third turnover is where you hit 95% and the final turnover is just to get that last three percent up to 98%. If you do not understand this then you can not possibly make an informed decision about how many hours you need to run your pool pump.
Flow Volume - This is a subject that you are going to be hearing a lot about over the next few years in the world of swimming pools and pool filtration. With spring 2021 a new law is being passed that all swimming pools, both residential and commercial, will be required to have a variable speed pump. As part of this change, for the first time, pool owners will really want (need) to know how much water is moving through their system at any given time. Without knowing the value for flow then you can not begin to calculate your turnover rates, and you will leave savings on the table that you otherwise could get back into your pocket. For more information about this you can read this article about why swimming pools need flow meters. You could try to guess at your flow rates without a meter, but you will definitely be wrong about your numbers, and most likely you will be wrong in excess of 25% of your actual flow rates. You will be forced to get a new variable speed pool pump at some point, but whether you actually experience energy savings will be up to you, and the way you do that is by learning about your flow rates and then building a schedule for your variable speed pump that meets your turnover rates (including the flow needed for the peripheral equipment you have). To see an example of how this works you can read this article about programming a variable speed pump.
Pool Volume x 3 (or 4 for a 98% filtration total)
Divided by the number of hours you run your pump
Divided by 60
This calculation will let you know the flow rates that you have (or need) to meet the turnover rate requirement for your pool. Using a 10,000 gallon pool as an example, we need 30,000 gallons per day to turnover the water three times and filtration of 95% of the water in your pool. If you run your pump 24 hours per day you would divide 30,000 by 24 and then divide by 60. That is about 20.8 gallons per minute. If this example pool had a variable speed pump you could have the RPM very low over 24 hours and you could meet this 30,000 gallon requirement using very little power.
With a single speed pool pump you might take the 30,000 gallon number and divide by less than 24 hours. Perhaps 12 hours, which means you run your pump for half the day instead of all day. Or even 8 hours per day as a minimal filtration schedule. 30,000 divided by 8, divided by 60 is about 62 gallons per minute. This number is something that you might see in a small pool with 1.5" plumbing lines, combined with a 1 horsepower or perhaps a 1.5 horsepower pump. If you had a single speed pump you definitely move a lot of water per hour, but the cost of doing it is very high. There are a lot of advantages to you and your pool to allow the water to run for longer, like 24 hours per day, but at much slower speeds where water moves more efficiently and without as much friction loss in the plumbing lines.
So how many hours per day should you run your pool pump? You should run your pool pump until you have filtered the volume in your pool three times (or four times) and ideally this would be based on a 24 hour filtration schedule where the pool does not have any periods of down time where the pump is off. With single speed pumps this is not realistic as the costs to run 24/7 are too great, and you would likely be far exceeding even four turnovers per day so it would not be money well spent. It is important to note that simply meeting turnover requirements is not enough, and you should consider the amount of time the pool water sits stagnant. If you can meet your turnover needs in four hours with a big filtration system that is 20 hours consecutively the pool sits stagnant. It would be a far better plan to use mechanical timers to program a filtration schedule that runs at least two times per day to split up the periods of time the pool is sitting stagnant. I hope this helps to clear up some of the confusion about how to figure out how many hours per day you need your pump to run.
This article also highlights the importance of flow meters and how they help to take the guess work out of flow rates - something that is critically important if you want to get the most return out of your investment in a new variable speed pump. For more videos like this that help teach you, and show you, how pool pumps work and how to get the most out of yours, please be sure to subscribe to my YouTube channel.
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