Pool Pump Sizing: Signs of Improper Size and How to Calculate the Right Size for Your Pool

Swimming pool pumps are a required element on your swimming pool.  As the water is drawn from the skimmer and/or main drain, it gets pushed back through your system, making stops along the way.  You may have a salt cell, heater or in-line chlorinator.  You most certainly have a swimming pool filter as this is another required piece of swimming pool equipment.  As the water passes through, depending on what you have, it gets sanitized, heated and cleaned before it returns back into your vessel.  

How Are Swimming Pool Pumps Sized?

When you think “size”, your mind may automatically go to dimensions.  While pump dimensions can be important, especially on an equipment pad with limited space, when we talk about pump size we are actually referring to the maximum horsepower. Pumps are measured in horsepower.  They can vary from very small sized, such as .5 hp to larger sizes like a 3 hp.  They make greater horsepower pumps, used on commercial bodies of water, but for residential pools, typically the largest size pump would be a 3 hp.

Single Speed Pool Pumps

These are now considered old technology.  These type of pumps run on only a single speed.  That speed is measured in revolutions per minute (RPMs).  The RPM of a single speed swimming pool pump is 3,450 rpm.  These machines are not energy efficient and use a lot of electricity.

Two-Speed Pool Pumps

While slightly more efficient than a single speed pump, these pumps are going by way of the dinosaur.  They have a high setting and a low setting.  Only saving you money on the lower speed, they don’t make a whole lotta sense in this day and age of swimming pool equipment.

Variable Speed Pool Pumps

Ahhh…now you are speaking my language!  These modern versions of swimming pool pumps are the only way to go, in my opinion.  They run at just that–variable speeds.  What does this mean?  Well, they can be programmed to run at a variety of RPMs, thus changing the horsepower.  You can run these pumps up to their Greatest  Maximum Horsepower.  At this speed, they are operating at 3,450 RPMS like your single speed used to.  Kinda.  They are still more efficient, even at 3,450 RPMs.  

This is contributed to things such as having a permanent magnet motor.  Also having a motor that is totally enclosed and fan-cooled.  You will run your variable speed longer at a lower speed.  This makes for energy savings.  

Energy Savings= Lower Electric Bill= More Money in Your Pocket= More Donuts

Okay, maybe you aren’t a donut fan (I am), but insert whatever word you want into the formula.  The point is:  THEY SAVE YOU MONEY!  Think you can’t afford the investment that pays for itself?  Think again.  You can get a name brand, quality, American made variable speed pool pump for about half of what your local swimming pool store would sell them for.  Yes, Black & Decker has extended their long running expertise to swimming pool equipment. With a 5 year warranty, what have you got to lose?  Besides those pesky, high electric bills, that is.  Check them out here.

If You Have Low Pressure

If you have too small of a pool pump, you will notice certain things.  For instance, your automatic pool cleaner will barely be moving.  Your water won’t be as clear.  Water clarity requires proper circulation, as does water safety.  One could drown in a cloudy pool!  Yikes!  We need to accomplish what is known as a turnover.  A turnover is when the amount of gallons in the swimming pool is equal to the amount of water passing through your filter.  We aim for at least once a day.  Your chemicals mix and properly work when the water is being circulated.  When do we need our chemicals most?  During the hottest part of the day.  We need our chemicals, especially our sanitizer, to work efficiently to keep our families safe.

If You Have Too Much Pressure

If you have too large of a swimming pool pump you will notice different things.  If a water feature is part of your set-up, you may experience gushing versus a gentle flow.  The sound it makes will be LOUD.  That is all of the water attempting to go through your plumbing.  This could lead to some serious damage.  

Another place you might see damage is within your swimming pool filter.  Too large of a pump could cause the pressure gauge to read high, even when the filter is cleaned.  This high pressure can lead to broken grids, ripped cartridges and a cracked manifold.  In crazy severe cases, the lid of your filter could go flying off like a rocket ship!  This could be deadly.

So, we see the importance of having the right sized pool pump.  The great thing about variable speed pool pumps is it is okay to oversize them because you can dial it down, meaning run it on a lower RPM and gain even MORE donuts–I mean savings.  Ahem.  See you poolside!