How To Calculate The Correct Size Swimming Pool Pump

How important is it for you to have a clear, clean and safe swimming pool water to relax in, exercise or have lots of people over for a pool party? If it matters to you, then you need to keep reading because having the proper size pool pump will make all of this possible. The pool filtration system is a vital componant for maintaining a crystal clear pool.

It is recommended to circulate your pool once a day so the pump and filter can turn over the total gallons of the pool at least one time. In order for your pool system to do this efficiently, you need to have the correct pump for the plumbing being used and a filter that can handle the flow rate.

You don’t want a pump that is too powerful or one that’s undersized because it won’t be able to properly filter your pool. Both of these situations can harm your pump and/or filter.

If you are not sure you are getting the right pool pump, continue reading and by the end of this article you will be able to buy the correct pump with confidence. The first thing you will need to know is how many gallons of water is in your pool.

Here’s a great video to explain the correct sizing of an above ground pool pump.

Step 1 How To Calculate Gallons In A Pool

To figure the gallons in a pool, you will need to take some measurements. It helps if you have a calculator handy. You can use the one on your phone but be careful not to drop it in the water. I have had this happen to me.

Here are the formulas for the various pool shapes.

Square and rectangle pools are Length x Width x Average Depth x 7.5 = Total Gallons

Ovals, Round and Kidney pools are Length x Width x Average Depth x 5.9 = Total Gallons

To figure the average depth you would add the depth of the shallow end to the depth of the deep end and divide by 2. Here’s an example. Say the pool is 8′ at the deep end and 3′ at the shallow end. This would be 8 + 3 = 11 divided by 2 = 5.5

Here is a simple pool calculator if you are having problems.

Step 2 What Is The Minimum Flow Rate For Your Pool?

Now we need to calculate the minimum flow rate to keep your pool clear and filter clean. To do this take the total gallons of your pool and divide by the number of turnover times (usually this is 8 – 10 hours) then divide that number by 60. For example: 20,000 gallons with a turnover rate of 8 hours would be 20,000 Gal. divided by 8 = 2500 divided by 60 = 41 gallons per minute.

Step 3 What Is Your Maximum Flow Rate?

Moat pools are plumbed with 1.5″ or 2″ PVC pipe. The smaller 1.5 pipe will allow up to 42 gallons per minute of flow and the 2″ has a maximum flow rate of 73 gpm. You will want to make sure the plumbing is as big as the suction and discharge ports. They should never be reduced.

Step 4 What is the Maximum Flow Rate Of Your Filter?

Filters are not made for a one size fits all so you want to be careful and not get a pump that will move more water than your filter can handle. You should be able to look at the flow rates on the filter itself or in the owners manual. Pay close attention to these recommended flow rates and not to exceed them.

We have just figured the maximum and the minimum flow rates for your pool. You can now buy the correct pool pump for your system and keep your pool operating properly. This will give you the proper circulation for your pool and will save you in headaches, time and money. It really doesn’t take that much time or effort to be sure you are getting the right swimming pool pump for the size of your pool.

Now that you have the peace of mind knowing how to size your pump, you will also need to perform the proper maintenance for the type of filter you have. Follow the maufacturer’s directions for cleaning and maintaining your pool filter. Keep in mind that this is only part of keeping your pool water clear. You will still need to maintain proper water chemistry. If you do these 2 things, you will enjoy your pool so much more.

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