How to Choose the Best Pool Pump
For a first time pool owner, shopping for a pool pump can be a very daunting task. With a myriad of terms to memorize and items to consider, it’s no wonder that many of us end up at the mercy of the local pool maintenance guy or pool shop. In order to level the playing field as you work to find out just what you need and what you don’t, we’ve put together some helpful information on how to find the best pool pump for your needs.
There are two key elements that play into determining what pool pump (and how strong it needs to be) will best work for your system – ‘flow rate’ and ‘head.' ‘Flow rate' refers to the water quantity that can move in a certain time frame and is measured in gallons-per-minute (or GPM). The term-‘head’ refers to the amount of resistance to flow that exists in your pool plumbing system. Head is usually measured in ‘feet of resistance’ or ‘feet of head.’ The items in your circulation system (such as a heater, automatic pool chemical feeder, etc.), as well as the amount of bends in your piping, size of piping, and distance the water must travel all play a role in determining the total head.
Pump manufacturers carry details related to flow rates and head that can help you determine which pool pump you need. It’s also important to keep in mind that these two calculations are not independent of each other. Your determined/desired flow rate will play a part in determining your head, as many elements within a pool’s plumbing loop offer different levels of head depending on how much water you’re trying to pass through in any given moment.
Calculating Flow Rate: To calculate flow rate, you first need to determine your desired turnover rate, or how often your pump filters an equivalent amount of water to the total amount in your pool. We recommend that your pool has at least 1-2 turnovers a day with a turnover time of about 5 hours. The steps below will help you calculate your flow rate.
Determine your pool capacity using this article. Divide the number of gallons of water in your pool by the number of hours you want per turnover (say 5).Then divide this number by 60 to determine your need flow rate per minute (GPM).
Example: Let’s say we have a 20,000 gallon pool and have a desired turnover rate of 5 hours. Your desired flow rate would be: (20,000/5) = 4,000 gallons per hour/60 = 66.66 GPM (approx. 67 GPM).
Calculating Head: As mentioned above, your total head is comprised of a variety of factors and is actually broken into multiple parts, as head does have a dynamic component to it. These calculations can become very complex quickly. There is no need to worry; there are a few tips for estimating the total head. Please note: To estimate feet of head below, courser filters allow for lower-end estimations.
Determine the amount of pipe between the pump and pool return. This is your starting feet of head. If you use a filter, cut this number in half. If your return line pipe size (diameter) changes (reduced diameter), determine the percentage change and add that to your calculation (20 feet of pipe that connects to a 50% smaller diameter pipe adds 10 feet of head). 90-degree turns in piping add around 1-2 feet of head.
Other items might factor into this measurement and can usually add around 2-12 feet of head. Sometimes these products will tell you how much resistance is available depending on your flow rate. If you have that information or can contact a manufacturer, you will have an accurate estimation. For each foot below the water surface your return line is, add 1 foot of head to your calculation.
Buying the Pool Pump: You’re on your way to purchasing the right pump for you pool. First, you calculated the flow rate, then; you measured the head, now you can make the final decision! It might be a good idea to look over the manufacturer’s specs related to each pump in these two areas to determine the best pump for you. If you’re still not feeling confident enough to make the decision alone – contact us! We’d be more than happy to help you select a pump and answer all pool equipment or supply questions you might have.