How to Size a Pool Pump for Your Home Pool

More often than not, swimming pool owners make the mistake of buying larger pool pumps than they actually require. This leads to high operating costs and straining on their pool filters because of too much pressure. They do this because they lack the appropriate information regarding what to consider before buying them. Some important questions need to be asked before choosing and buying a swimming pool pump. These are:

1. What size pool pump do I need?

2. How big is my pool?

3. Is it above-ground or in-ground?

Factors to consider

1. Size of the pool

The size of the pool directly determines the pump size you need. It is measured in gallons and can be calculated using the following formula:

Length * Width * Average Depth * Multiplier

The multiplier for round or oval pools is 5.9 while for rectangular, square or free-form pools is 7.5

The average depth is calculated by summing up the shallow end depth and deep end depth then diving the sum by two. It is important to note that all these measurements are in feet.

The resulting value is what determines the pump size you need. The best practice is to circulate the water through the filters at least three times daily meaning that the pump should be able to pump all the pool’s water in 8 hours. Therefore, the size of the pool (in gallons) should be divided by 8 in order to get the flow rate per hour then divided by 60 to get the flow rate per minute. For instance, a rectangular pool measuring 50 ft by 20 ft with a deep end depth of 8ft and a shallow end depth of 4ft should have a pump with the following flow rate

20*10*(8+4)/2*7.5=9000 gallons

9000/8=1125 gallons per hour

1125/60=18.75 gallons per minute (GPM)

This means that you will need a pump with a flow rate of 18.75 GPM.

2. Pump speed

There are three types of pool pumps categorized according to speed. These are

•        Single speed pumps

This is very common and it runs continuously at one speed depending on its motor’s horsepower. It is highly inefficient because of constantly running at one speed (which is usually high speed) while you might require different speeds to suit your filtration needs or turnover time.

•        Dual speed pumps

Dual speed pumps give you the flexibility of choosing between high speed and low speed. High speed is used mostly when cleaning the pool or when there is a major issue while low speed is used on normal times (when the water is generally clean and requires slower turnover) saving on energy costs.

•        Variable speed pumps

This is the most efficient pool pump because it has a permanent magnet motor (similar to the ones used in electric cars) which has less friction as compared to the induction motors on the single and dual speed pumps. It allows you to set the flow rate at any speed giving you the most flexibility in cleaning your pool. Though expensive, this is the best type of pool pump and is recommended for its flexibility and efficiency.

3. Above-ground or in-ground pool

The type of pool determines where your filter will be located, which then determines the pump you need. If the filter intake is positioned above the pump, you will need a top-mount pump. On the other hand, if the filter intake is on the same level as the pump, you will need a side-mount pump.

4. Filter size

A filter’s size also determines which pump to buy. A large filter requires a large pump while a small filter requires a small pump. However, it is better to have a pump with a max flow rate that does not exceed a filter flow rate just to keep the system safe. The opposite however would be catastrophic because the pump will destroy the filter.

How to size a pool pump

A pool’s size greatly determines the pump size. However, other factors also contribute to ultimately determining the pool pump size. These include the resistance from the filters and plumbing. Water passage through the filter produces resistance. As the filter gets used for a long time, it gets clogged with debris which further increases its resistance.

Similarly, the plumbing around the filtration system might include many bends or a large head which causes a significant resistance to water flow. Hence, it is recommended to get a pump with a slightly larger flow rate to cater for any form of resistance and give you the required turnover time.

How to choose a pool pump

Popular brand pool pump are the safest bet because of their durability. A good example would be Onga pool pumps such as this specifically designed Onga Pantera Ppp750 pool pump. Onga pool pumps are high quality pumps which are known for their reliability and exceptional performance.

How to buy a pool pump

With all the information above, it is time to buy the pump. Many manufacturers provide details of their pool pumps on their websites and this is a good place to compare the pumps specifications with the specifications you want.

In this case, Onga pool pumps are clearly listed and classified as filtration and specialty pumps on their website where you can compare specs then purchase from their dealer shops.