Pump Run Time

[Steve456]

I have not seen a discussion of the number of hours each day a pool owner should run their pump. Pool stores have told me that a pump should run 8 to 12 hours per day. Or I have been told you should have one complete turnover of the water each day. But nobody has said why! Or how this was determined.

I would think that factors such as the amount of debris that is blown into the pool, your Cl level, number of swimmers, type of filter media would effect the required run time. Is there an advantage to running the pump for several hours in the morning, afternoon, and night instead of a straight 8 hour period. Our utility does not have time of day billing so that is not a factor.

Just as pool builders are known to over size pumps to make it seem they are providing top of the line equipment and they ignore hydraulics and efficiency I wonder if required pump run times are exaggerated. In a simpler time when electricity rates were low, the world seem to have unlimited energy, and no one thought that man induced global warming was even a possibility it made sense to encourage pool owners to have long pump run times.

We no longer live in a simpler time. I have at times run my pump for only 4 to 6 hours a day during the summer with no algae and maintained crystal clear water. Yes, I violated the advice I received from everyone. I am questioning the standard advice since my experience so far says the recommendations are excessive, I do not want to waste energy and cause more CO_2, and a want to determine a standard number of hours to run my pump before I install a SWG.

So my question is not how many hours do you run your pump but what problems does a pool owner have if they do not run their pump sufficient number of hours. Should you determine the sufficient number of hours by trial and error?

Since your pool pump, A/C, and refrigerator are three of the largest electricity using devices in your house if all pool users reduced their pool pump run times just an hour per day a significant amount of energy could be saved. I would appreciate thoughtful knowledgeable advice.

TIA

 

[JasonLion]

The actual pump run time you need depends on the relative size of your pool and your pump/filter, which varies from pool to pool. So each pool owner needs to figure it out for themselves.

A good rough rule of thumb is that your pump run time should be around one turnover. That means pumping the same number of gallons of water as your pool contains. If you know the number of gallons per minute (GPM) for your system, that is a good place to start. Unfortunately, most pool owners don't know their GPM, and it isn't easy to figure out without a flow meter or other special equipment. In that case, a good starting assumption for a single speed pump would be to try a 12 hour run time, and for a two speed pump running on low would be 24 hours.

To find out what your ideal run time is, you need to experiment. Start with a run time that is higher than you think you need and get the water really sparkling. Then, try running the pump for a week at a different run time and watch the water closely to see how it looks. If you are running the pump too little, the water will lose it's sparkle. Note that it is best not to try any of this when you are just starting out, or when you are having any kind of algae problem. Also, if you have a SWG, remember that the SWG % setting will need to change any time you change the pump run time.

One other factor to keep in mind is that the required pump run time depends on the water temperature. The colder the water the less you need to run your pump. A good rule of thumb is to decrease your pump run time by 10% of your mid-summer run time for each 10 degrees colder the water gets. Of course the ideal run time will vary depending on various factors, so experiment a little and only use that as a starting point.

 

[mas985]

For an average plumbing system, you should get about a 6 hour turnover with that pump.

 

[Steve456]

My turnover time is approximately 8 hours.

Jason from your post I take it that water clarity not algae or other problem is the limiting factor for determining the minimum time to run the pool pump. Does that suggest that a person with a DE filter or other efficient filter media would have to run their pool pump for less time?

Why does the required pump time depend on water temperature? If the limiting factor is filtering matter out of the pool then temperature would not seem to be a factor. Water temperature would be a factor if algae is the limiting factor but then your Cl level would be a factor to determine pool pump run time.

 

[mas985]

My turnover time is approximately 8 hours.

Jason from your post I take it that water clarity not algae or other problem is the limiting factor for determining the minimum time to run the pool pump. Does that suggest that a person with a DE filter or other efficient filter media would have to run their pool pump for less time?

Why does the required pump time depend on water temperature? If the limiting factor is filtering matter out of the pool then temperature would not seem to be a factor. Water temperature would be a factor if algae is the limiting factor but then your Cl level would be a factor to determine pool pump run time.

So that must be a 1 HP uprated pump with 1 1/2" plumbing? Seems a bit on the low side so I was just curious. What filter pressure are you at?

Also, I can think of three primary reasons for pump run time. Add enough chlorine to the water, keep the water mixed (i.e distribute the chlorine to all parts of the pool), and filter out particulates.

Warmer water generally means more things to kill in the water which means more chlorine is needed as well as distributing it and filter it out so a longer run time is useful for all of the three criteria.

The first two criteria keep algae and bacteria in check so as long as you can meet the first two criteria and you don't care about the third, you can shorten pump run time as much as you want. However, there will become a point where the water will start to get cloudy and less appealing.

 

[JasonLion]

Water clarity is a good measure of algae activity, the two are tightly linked. Low levels of algae will give the water a slightly dull appearance, even though the water remains clear (at least at first).

Required pump run time tends to go down as water temperature goes down for a couple of reasons. Algae grows more slowly when the water is colder, so there is less dead algae to filter out. Also, pollen, the most common source of airborne "dirt", tends to go away as the temperature gets colder. Also, people don't tend to swim as much as the water gets colder, so less swimmer borne dirt to filter out.

There are really two primary reasons we run the pump/filter. The first is to have good water clarity. The second is to insure good water mixing and chemical distribution. Water clarity takes more pump run time than mixing and chemical distribution do, so it is water clarity that mostly determines pump run time. Water clarity is also something you can determine yourself just by looking, without test equipment or complicated math.

The main complicating issue is that improper chemical levels or the filter getting too dirty can both throw off the relationship between water clarity and pump run time. Also, remember that once in a while, a SWG or pool heating will put a lower bound on how short you can make the pump run time.

 

[Steve456]

Mark, I am impressed. You made an educated guess.

My pump is a Hayward Super II Pump Model SP3010EEAZ 1HP. rated at 50 gpm Unfortunately my pipes are 1 ½". When I went to replace a pump I found an article on hydraulics which convinced me that a 20 HP (just kidding) pump would not move much more water through my 1 ½" pipes. I realized that the builder had never read an article on pool design and I decided that I had to take ownership of my pool.

I thought about re-plumbing the pipes to 2” for about 1 second when I realized I could not do anything about the skinny pipes under the pool.

Filter pressure? I do not believe that my pressure gauge is working properly. I plan to replace it this summer because I could not think of a way to properly test the existing pressure gauge.

 

[mas985]

Steve,

Did the pool store tell you that you had an 8 hour turnover or did you calculate that yourself?

Filter pressure is a pretty good estimate of return head loss. Without it, it is hard to guess total head loss and flow rates so I was curious how you determined that you had an 8 hour turnover.

An 8 hour turnover is 62.5 GPM for a 30k pool which would be about 70 ft of head loss according to these specs. This usually results in fairly high filter pressure > 20 PSI which is why I asked about that.

 

[Steve456]

Mark, I calculated the turnover myself. When I installed a new pump I calculated a 10 hour turnover. I mis-remembered and said the turnover was 8 hours.

Now that I look at the performance data you referenced I do not see how I determined 50 gpm. I remember looking at a head curve to determine the gpm but I now question what I did. How should you determine gpm?

 

[mas985]

Mark, I calculated the turnover myself. When I installed a new pump I calculated a 10 hour turnover. I mis-remembered and said the turnover was 8 hours.

Now that I look at the performance data you referenced I do not see how I determined 50 gpm. I remember looking at a head curve to determine the gpm but I now question what I did. How should you determine gpm?

GPM can be determined in one of couple different ways.

First, a flow rate meter can be installed but it is somewhat costly and not necessary to get a ball park number.

The second method is to use measurements from your current set-up. This is described in more detail in this sticky. By using the filter pressure and a suction measurement (optional), you can determine head loss and then look up the flow rate on the head curve of the pump. If you don't have a vacuum guage, there are some estimates you can make for the suction side based upon your setup. But the most important thing is to get a fairly accurate filter pressure.

Another option is that I can use your plumbing design and run it through a head loss model that I developed to estimate your plumbing head loss. But I would need to know the number and length of runs from pool to pad for both the suction and return. This method is not as accurate as mesuring the suction and pressure but it will get you pretty close.

If you have only one suction line and one return line at 50' in length, then you get close to 52 GPM @ 75' of head. However, if you have two suction lines, the flow rate goes up to 59 GPM @ 71' of head. So it depends on the setup you have.