How to correctly size a pool pump for your swimming pool

It is important to carefully evaluate your pools needs before deciding on a replacement pump.

This is because pumps are a lot more efficient than they used to be and you run the risk of oversizing the pump if you simply go by horsepower ratings.

To assist you in your pump selection, we have included a brief synopsis of each type of pump along with a comparison chart on the bottom of the page. We have also included ratings on each pump.

Once you narrow down your selection, click on the brand to go to that brand's page for even more product information.

## How do I choose the right pump?

**There is no guarantee that your pool builder sized the pump properly to begin with.** In the Dallas area, for instance, the builders are notorious for putting 2 horsepower pumps on everything because the next guy does. Nobody wants to lose a sale because they sized the pump smaller.

Properly sizing the pump involves several steps as described below. If you do this, you will avoid wasting electricity and extra wear on the other equipment.

## Step 1: Determine the MINIMUM FLOW RATE.

This factor calculates the minimum flow rate that must be maintained in order to circulate all the water in the pool through the filter within a certain number of hours, otherwise known as the "turnover time".

A good turnover time for a home pool is usually 8-10 hours. A heavily used pool will need to have a shorter turnover rate. Once you know the desired turnover rate, you can determine your desired flow rate.

Use the following equation to determine the desired flow rate:

- Pool Size - number of gallons of water in the pool.
- Turnover Time - time to move entire capacity of pool through filter.
- Flow Rate - desired flow rate in gallons per minute.

Pool Size (US Gallons) | Turnover (Hours) | Minimum Flow Rate |
---|---|---|

35,000 | 8 Hours | 73 GPM |

35,000 | 10 Hours | 58 GPM |

24,000 | 8 Hours | 50 GPM |

24,000 | 10 Hours | 40 GPM |

18,000 | 8 Hours | 38 GPM |

18,000 | 10 Hours | 30 GPM |

The following chart is another way to help calculate the desired flow rate.

If you have a 25,000 gallon pool and want a turnover rate of 8 hours, then you will need a pump with a flow rate of 52 gallons per minute/

If you have a 35,000 gallon pool and want a turnover rate of 10 hours, you will need a pump with a flow rate of 56 gallons per minute.

For this situation, we will use a 24,000 gallon pool with a turnover time of 8 hours, giving us a MINIMUM FLOW RATE of 50 gallons/minute.

## Step 2: Determine the MAXIMUM FLOW RATE.

The flow rate through any given pool system is limited by the size of the piping and the equipment. This determines the maximum flow rate through the system.

**The first thing to check is the pool system plumbing.** For instance, the maximum flow rate through a 1.5 inch PVC pipe is 44 Gallons per minute. Even if you have a pump that can move 100 gallons per minute, it will do very little good if the piping will only allow 44 gallons per minute through it. An oversized pump will actually strain against the piping and can be damaged in the process.

#### Check the PLUMBING FLOW RATE

As a general rule, the velocity of the water through the pipe should not exceed 7 feet per second. The chart below shows the maximum flow through different sizes of pipe.

Count the intake lines and you will see what the maximum flow into the pump will be.

For each 2.0 inch intake line, the maximum flow into the pump will be 73 gallons per minute (GPM).

For each 1.5 inch intake line, the maximum flow into the pump will be 42 gallons per minute (GPM).

Make sure the the lines going back to the pool will also support the same level of flow.

In the diagram to the right, the system is plumbed in 2.0 inch pipe. Since the system can be run in either spa or pool mode, you have to calculate the flow rate each way.

- Spa Mode - 73 GPM (One 2.0" pipe)
- Pool Mode - 146 GPM (Two 2.0" pipes)

The maximum flow is the lower of the two, which would mean a MAXIMUM PLUMBING FLOW RATE of 73 gallons per minute (GPM).

#### Check the FILTER FLOW RATE

Another limiting factor is the pool filter. Each filter has a maximum flow rate. If you exceed that maximum flow rate, the filter will not operate properly and can be damaged as a result.

#### The proper filter flow rates are as follows:

Recommended flow rates for different sizes of SAND FILTERS | |||||
---|---|---|---|---|---|

Tank Diameter | 19 " | 21 " | 24 " | 30 " | 36 " |

Surface Area | 1.8 Sq. ft. | 2.3 Sq. ft. | 3.1 Sq. ft. | 4.9 Sq. ft. | 6.9 Sq. ft. |

Max Flow Rate | 40 GPM | 50 GPM | 60 GPM | 100 GPM | 140 GPM |

Recommended flow rates for different sizes of D.E FILTERS | |||||
---|---|---|---|---|---|

Surface Area | 24 Sq. ft. | 36 Sq. ft. | 48 Sq. ft. | 60 Sq. ft. | 72 Sq. ft. |

Max Flow Rate | 48 GPM | 72 GPM | 96 GPM | 120 GPM | 144 GPM |

Best Flow Rate | 36 GPM | 54 GPM | 72 GPM | 90 GPM | 108 GPM |

Recommended flow rates for different sizes of CARTRIDGE FILTERS | |||||
---|---|---|---|---|---|

Surface Area | 100 Sq. ft. | 200 Sq. ft. | 300 Sq. ft. | 400 Sq. ft. | 500 Sq. ft. |

Max Flow Rate | 38 GPM | 75 GPM | 112 GPM | 150 GPM | 150 GPM |

Best Flow Rate | 30 GPM | 50 GPM | 75 GPM | 100 GPM | 125 GPM |

In this particular system, if you have a 48 square foot DE filter (see yellow highlighted area above), your MAXIMUM FILTER FLOW RATE would be 96 gallons per minute. In a perfect world, we would try to keep the flow rate down near 72 gallons per minute, but for now we are dealing with the maximum flow rate.

- Maximum plumbing flow rate - 73 Gallons per minute.
- Maximum filter flow rate - 96 Gallons per minute.
- The overall MAXIMUM FLOW RATE is the the lesser of the two - 73 gallons per minute.

## Step 3: Choose an IDEAL FLOW RATING for your new pump.

After you have calculated the MINIMUM FLOW RATING required to meet the turnover requirements of the pool, and after you have calculated the MAXIMUM FLOW RATING based on the limitations of the filter and piping, you are ready to select the proper size pump.

Draw a simple chart like the one below. Mark the MINIMUM FLOW RATING and the MAXIMUM FLOW RATING. The space between the minimum and maximum flow rate is the ideal range.

If you have a pool with no attached spa, you can choose a pump on the lower side of the ideal range. It will be sufficient to properly filter the pool without wasting energy in the process. In that case, we would look for a pump in the 50 - 60 GPM range.

If you have a pool/spa combination, you need to consider the flow requirements of the spa jets. This will often push you towards a pump on the higher end of the acceptable scale. In that case, we would look for a pump in the 75 GPM range.

If you have a pool/spa combination, you might want to consider a 2 speed pump. It can run on low speed while it filters the pool, and then switch to high speed when using the spa.

## Step 4: Look at the POOL PUMP RATINGS to find the right pump

Once you have decided to buy a new pump, take some time to research your options..

Don't just assume that you need the same horsepower pump as you now have.

The sample pump chart on the right shows the pump curves for different sized pumps.

Suppose your system has 60 feet of head and you want a pump that will deliver 50 gallons per minute.

We have added a yellow line denoting 60 ft of head, and a blue line denoting 50 GPM. Find where the two lines cross and you will see the pump that will deliver the desired rate of flow.

From this chart, you can see that a 1 horsepower pump (the green curve) will give you 52 GPM flow on a system with 64 feet of head.

We have tried to give you the flow information on each pump so that once you come up with a rate of flow, you can come up with the proper pump, the first time.

Note: Figuring out feet of head (below) is difficult. Typically a in-ground pool will have 50-60 feet of head pressure and an above ground pool will be somewhere around 30 feet of head. These are only approximations.

#### What about 'FEET OF HEAD' ? What does that mean?

The total resistance to flow is measured in "feet of head". As you can tell from looking at the pump charts, the greater the resistance to flow (expressed in feet of head), the lower the flow rate. The greater the resistance to flow, the more powerful the pump needs to be to overcome it.

The resistance is measured in "feet of head". The best way is to approximate the resistance is as follows:

- 1. Measure the vacuum pressure at the pump and multiply by 1.13. - A reading of 12 inches mercury times 1.13 equals 13.5 feet of head.
- 2. Measure the clean filter pressure and multiply by 2.31. - A reading of 22 times 2.31 equals 51 feet of head.
- 3. Add the two together to get total friction loss in feet of head. - A reading of 13.5 plus 51 equals roughly 64 feet of head.

#### Still not sure what size pump you need? You can request a pump size recommendation specifically for your pool

#### Start shopping for your new pool pump.

## FAQs

### Is it OK to replace a 1hp pool pump with a 1.5 HP? ›

So to answer the question, **yes, you can replace your 1hp pool pump with a 1.5hp pool pump, but only if your situation calls for it**. If you've determined that your current pump is too small for your pool, then we'll suggest replacing it with a larger ECO pump like the Water TechniX Pump Alpha ECO.

**What HP pump do I need for a 15000 gallon pool? ›**

For example, let's say we have a 15,000-gallon pool. If we're wanting a pump that can provide an 8-10 hour turnover, we'd need something rated for a minimum of **1,500-1,875 GPH or 25-31 GPM**.

**How big of a pool pump do I need for a 30000 gallon pool? ›**

So, for a 30,000-gallon pool that runs continuously (24-hours), the formula is: **30,000 x 2 ÷ 24 ÷ 60 = 41.6** or rounded up it's a 42 GPM minimum flow rate.

**What size pump do I need for a 20000 gallon pool? ›**

**(Pool capacity in gallons/desired turnover rate in hours)/60=Flow rate in GPM**. Example: If you have a 20,000 gallon pool and 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, or approximately 67 GPM.

**What happens if you oversize your pool pump? ›**

A pool pump that is larger than needed has a more powerful motor and circulates water at a higher flow rate. This uses significantly more energy to pump the same amount of water and puts additional stress on your pipes and filter, meaning **you'll need to replace them sooner**.

**Can a pump be too strong for a pool? ›**

**The maximum flow rate for your pool pump should not be more than the maximum flow rate of your pool's filter**. If your pool pump pushes more water through the filter than it can handle, the filter won't work correctly.

**What size pool filter do I need for a 15000 gallon pool? ›**

So for a 15,000-gallon pool, I suggest a **300 sq ft filter**, for a 20,000-gallon pool a 400 sq ft filter and for a 30,000-gallon pool a 500 sq ft filter. You can use a smaller filter if you choose, just note that you will be cleaning it often and the water flow may not be as efficient as going with a larger filter.

**How long should I run my pool pump for a 10000 gallon pool? ›**

The rule of thumb for pool maintenance is to run your pump for **eight hours per day**. That's the short answer, but it isn't always accurate. Other factors might shift this number.

**How long should you run a filter for a 15000 gallon pool? ›**

Here is an example to help you understand: For a 15,000 gallon pool, the pump is able to push 40 gallons per minute of water through the filter. That equates to 2,400 gallons per hour. At this rate it will take your pump **6.5 hours** to filter the whole 15,000 gallons.

**How much does it cost to fill a 30000 gallon pool? ›**

...

Basic per-Gallon Formula.

Pool Size by Gallon | Cost |
---|---|

15,000-gallon pool | $135 |

20,000-gallon pool | $180 |

25,000-gallon pool | $225 |

30,000-gallon pool | $270 |

### How many gallons of chlorine do I need for a 30000 gallon pool? ›

If not, here is how to calculate the amount of chlorine needed. It takes 1 ounce of chlorine in 7,500 gallons of water to equal 1 ppm. We will **divide 30,000 gallons by 7,500 to get 4**. It requires 4 ounces of chlorine to raise the parts per million of this example pool by 1.

**How much does it cost to run a pool pump 24 hours a day? ›**

Example 115 volts X 15 amps = 1725 WATTS. MULTIPLY the hours per day that you run your pool pump by the kW. This total will be the kWh -kilowatt hour per day Example 24 hours a day X 1.725 kW = **41.40 kWh per day**.

**How do I calculate what size pool pump I need? ›**

You **take the gallons divided by your turnover rate.** **Then take that number and divide it by 60 (for minutes) and you will get your required gallons per minute**. Then you will need to know the average feet of head. Total dynamic head is basically the resistance and length your pool pump needs to push the water through.

**What size heat pump do I need for a 15000 gallon pool? ›**

Pool Size (Feet) | Summer 4 BTU's | Spring & Fall 5 BTU's |
---|---|---|

Up To 10,000 Gallons 12' x 24' | 50,000 BTU | 50,000 BTU |

Up To 15,000 Gallons 14' x 28' | 85,000 BTU | 85,000 BTU |

Up To 20,000 Gallons 16' x 32' | 85,000 BTU | 110,000 BTU |

Up To 25,000 Gallons 18' x 36' | 110,000 BTU | 125,000 BTU |

**How do I calculate what size pump I need? ›**

So, to determine what flow rate you need, simply divide the total water capacity of your pond by 60. For example: With a 7000 litre fountain, simply divide 7000 by 60 = 116.6. In this case, you need a pump with a flow rate above 116.6/LPM.

**Is it OK to let pool pump run continuously? ›**

One of the biggest questions when it comes to regular maintenance is the swimming pool pump. **It's not necessary to have your swimming pool pump running at all times, as this can be a serious expense on your electric bill**.

**Is more HP better for pool pump? ›**

**The higher the horsepower, the greater volume of water pumped**. Additionally, the faster it'll filter through your pool water. This may be America, but even so: bigger doesn't always mean better. The fact is that a typical residential pool can be circulated effectively with just 1 HP.

**Is it OK to run pool pump 24 hours a day? ›**

Some commercial properties require 24-hour a day pump circulation, but as a homeowner, this is not advisable. **If you are lucky enough to own an Energy Efficient, Variable Speed swimming pool pump (VSP) then , yes, technically you could run your pump for 24 hours a day**.

**What ruins pool pumps? ›**

Pool pump motors are continuous-duty outdoor rated motors, but they will eventually wear out and break down. What causes it? **Running the pump dry, failure to perform regular filter cleaning or necessary repairs, and improper water balance** can all lead to premature motor failure.

**How many hours a day should I run my pool pump? ›**

The rule of thumb is generally **8 hours**, although it could be anywhere from 6-12 hours, depending on your pool's size. Each pool is unique, so to keep your pool pump efficient and effective, you need to figure out exactly what your pool's turnover rate is.

### How much chlorine do I need to shock a 15000 gallon pool? ›

Typically for granular shock, you'll need **one pound for every 10,000 to 13,500 gallons of pool water**.

**How many pounds of chlorine do I need for a 20000 gallon pool? ›**

For example, using the table above, a 20,000 gallon pool would require **7.8 lbs** of cal-hypo to increase the levels by 30 ppm. Check for proper water balance, especially pH in the range of 7.2–7.6, before adding the shock to the pool.

**How many chlorine tablets do I need for a 15000 gallon pool? ›**

Since a single tablet can treat 5,000 gallons of water, you'd only need **3 tablets** to treat up to 15,000 gallons.

**Is it better to run a pool pump at night or day? ›**

**The best time to run your pool pump is during the warmest hour of the day**; however, keep in mind that this means you will have higher energy consumption, which may lead to an increase in your electric bill. If you want to save on your energy costs, you can run your pool pump at night to avoid peak hours.

**Should I run my pool pump when it rains? ›**

Should I run my pump while it's raining? Zagers says **yes!** **We recommend that our customers run their pumps rain or shine UNLESS you have an electrical storm**. In that case, lightning could strike an outside circuit, which could damage your pump and other equipment.

**How many gallons per minute should I set my pool pump? ›**

What you're looking for is a pump that will be able to pump all the water in your pool through the filter in no more than 8-10 hours. This typically looks likes **40 GPM (gallons per minute) for smaller pools and 80 GPM for larger pools**.

**How many hours a day should a 10000 gallon pool run? ›**

Every pool must turn over at least once a day, so most pool pumps should run approximately **8 hours a day**.

**Can I turn my pool pump off at night? ›**

It may be cheaper to run the pump at night, but honestly **you should run it 1 hour a day per 10 degrees of temperature at least, and it should be during the day**. Running the pump at night should only be when you are doing a major chemical treatment such as algae clean-up.

**How many hours a day should you run your filter? ›**

We recommend that you run your pool filter for **at least 12 hours per day**, allowing all of your pool water to be run through the filter at least once each day. That being said, the more you run the filter, the cleaner your pool will be.

**What is the cheapest way to fill in a inground pool? ›**

**Filling your pool with dirt** is the fastest and most affordable way to get rid of a pool because there's no need to remove your concrete or metal shell. This saves on both labor and hauling costs. However, filling a pool with dirt is still a delicate process that requires careful preparation, drainage, and demolition.

### What is the cheapest way to fill a swimming pool? ›

What is the cheapest way to fill my pool? While it may not be the fastest way, **using a garden hose and city tap water** is the cheapest way to fill your swimming pool. The average American family uses 12,000 gallons of water per month. And the average-sized swimming pool is around 15,000 gallons.

**How many gallons of chlorine do you put in a 10000 gallon pool? ›**

You'll need about **52-104 oz** of liquid chlorine per 10,000 gallons of water. This amount should get the chlorine level to between 5 and 10 ppm.

**How many chlorine tablets do I need for a 10000 gallon pool? ›**

Chlorine tablets should only be a helping hand. Instead of filling your chlorinator or floater to the top with tablets, use **one three-inch tablet for every 10,000 gallons of water** in your pool. If you are shocking your water weekly, this amount of tablets should be perfect to maintain a good chlorine level.

**How many gallons of chlorine does it take to shock a 20000 gallon pool? ›**

For instance, if you pool is 20,000 gallons, you will add **4 pounds** of shock. Green or Dark Green Pool Water: This means there's a medium amount of algae in your water and you'll need to triple shock your pool. Triple shocking requires 3 pounds for every 10,000 gallons of pool water.

**How many times a day should pool water be turned over? ›**

A Rule of Thumb

This is based on the assumption that your average pool pump has a turnover rate of about 8 to 12-hours. That means that the total volume of your pool water will filter through your system 2 to 3 times per 24-hour period. For a residential pool the water should turn over **at least once per day**.

**How often should I shock my pool? ›**

HOW OFTEN SHOULD I SHOCK MY POOL? Shocking your pool regularly will help to keep the water clean and free of contaminants. You should aim to shock your pool **about once a week**, with the additional shock after heavy use. Some tell-tale signs that your pool needs to be shocked are cloudy, foamy, green, or odourous water.

**What is the average life of a pool pump? ›**

On average, pool pumps last **eight to 12 years** before needing replacement. Over time, it's normal for pool parts to begin to wear down. In addition, swimming pool technology has come a long way in the last decade.

**What is the difference between 1 HP and 1.5 HP? ›**

So, **on low speed the 1 HP moves 43 GPM and the 1.5 HP moves 45.5 GPM**. To save money you want to hopefully run it on low speed (much less electrical current is used on low speed and it's more quiet).

**Does pool pump horsepower matter? ›**

**The higher the horsepower, the greater volume of water pumped**. Additionally, the faster it'll filter through your pool water. This may be America, but even so: bigger doesn't always mean better. The fact is that a typical residential pool can be circulated effectively with just 1 HP.

**Are pool pump motors interchangeable? ›**

The motor on a pool pump will often fail before the pump itself needs to be replaced. Replacing just the motor is a common fix. **Motors are generally interchangeable amongst many types of pumps**, and there's currently no standard for replacement motors.

### How long should a 1.5 HP pool pump last? ›

On average, pool pumps last **eight to 12 years** before needing replacement.