Choosing The Right Swimming Pool Pump

The most important thing about choosing a swimming pool pump is NOT to pay too much attention to the HP(Horsepower rating)...heres some examples:

This 1 HP pump shown below pumps almost 100 GPM(gallons per minute) at 50 feet of total dynamic head(a measurement of friction the pump must overcome due to plumbing restrictions,pumping through the filter,heater,etc.) The pump shown below is a Jandy Stealth Pump. Later this year (2008), Jandy will be coming out with a multispeed permanent magnet motor version of this pump.

There ia also a less expensive version called the Jandy Plus HP that has one of the highest flow ratings in the below 1 HP class. The link below has more information if you wish to purchase one of these units:

Jandy In-Ground PlusHP Pump

1)The motor.The pump on top has a motor with a SF(service factor) of 1.65.You multiply the service factor times the HP(Horsepower)to get the rated HP of motor.1 x 1.65=1.65 actual horsepower.The lower pump has a SF of only 1

Also VERY important:the impeller on pump is matched to the motor specifications,so changing the motor HP or SF will not make a difference!

2)The design. The pump on top has a newer,much more efficient hydraulic design. The photo below shows the Jandy internal design-the basket is at left,the impeller is at right (red). The yellow throat section provides a gradual reduction in size from the basket to the impeller face....the hayward pump also has a similar throat section but it is much shorter and not as hydaulically efficient.

So the MOST important thing to pay attention to when choosing a pump is the pump's performance curve and the amp rating(amount of electricity used) The amp rating is usually expressed as a dual number(5.6/11.2) The lower number is for 230 voltage,the higher number 115 voltage. If there is only one value for amp rating,its a 230 only voltage motor. This information can be found online at most manufacturers websites.

When viewing the pump's performance curve,a good rule of thumb is an average pool has around 50 feet of dynamic head. There are ways to check this on your pool,but I will get into that on a later section on plumbing and hydraulucs.

So you just pick the pump that has the highest performance for the lowest amps? Not always-in older pools with 1 1/2" or 1 1/4" copper plumbing,you can actually strip the copper from inside the pipe due to friction from water velocity! An underground leak can be VERY expensive!I will also discuss the proper GPM for different size pipes in a later section on hydraulics.

As general rule,if you have 1 1/2" or smaller plumbing,and you are installing a modern,high efficiency,fully rated pump,(meaning high service factor) 1/2 HP is usually more than enough unless the pump is unusually far away or raised up from the level of the swimming pool,then a 3/4 HP may be needed. There may be exceptions to this - for example your plumbing is split between to suction lines and two return lines and you want equal flow to both at the same time or you may have solar panels on top of a two story house.


Here is a 1/2 HP pump I installed with a cartridge D.E. filter. The old swimming pool pump was I believe a 1 or 1.5 HP bronze pump. This new swimming pool pump and filter was a great improvement in flow and much less noise than the old system. Although I used 2" plumbing,you can see the pipe drops to 1 1/2" before it goes into ground. The return size was even smaller, 1 1/4" plumbing-I dared not go higher than a 1/2 HP pump!

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