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# Swimming Pool Calculations

When purchasing a new swimming pool or swimming pool product there are several calculations that can be helpful. Below are a few calculations that may help determine the size of your swimming pool, heater, filter, or many other products. Please select from the following calculations...

- The Surface Area of your Swimming Pool
- The Gallons of Water in your Swimming Pool
- The Horse Power Size of your Inground Swimming Pool Pump
- The Size of your Inground Swimming Pool Filter
- The Size of your Above Ground Swimming Pool Pump / Filter System
- The BTU Size of your Swimming Pool Heater

**Surface Area **The surface area of a swimming pool can help determine the BTU size of pool heaters.

Pool Shape |
Formula |

Rectangular |
Surface Area = L X W |

Round |
Surface Area = 3.14 X (D/2) x (D/2) |

Kidney |
Surface Area = .45 X (A + B) L |

**Gallons of Water**

Determining the gallons of water in your swimming pool can help determine such thing as the size of your pump and filter. The gallons of water depends on the shape of your pool.

**aD = Average Depth**

Pool Shape |
Formula |

Rectangular |
Gallons = Length x Width x Average Depth x 7.5 |

Round |
Gallons = Diameter x Diameter x Average Depth x 5.9 |

Oval |
Gallons = Long Diameter x Short Diameter x Average depth x 5.9 |

**The Horse Power of Inground Pool Pumps**

The three best manufacturers of pool pumps are Hayward, Pentair, and Sta-Rite. Each manufacturer sells different models of pumps. These models range in performance, and are rated by their Horse Power (HP). There are two important factors when trying to figure out which HP pump, the gallons per minute (GPM) and the Amount of head in feet. In order to figure out what ideal GPM you need for your pool pump follow these steps.

- To figure out the amount of gallons in your pool use this calculator
- A good rule of thumb is you should be able to clear your swimming pool in an 8 hour period of time. Take the number of gallons and divide that by 8.

**Ideal Gallons Per Hour (GPH) = Gallons of pool water / 8 **

- Next take the GPH and divide that by 60

**Ideal GPM = GPH / 60**

Now that you have the ideal GPM you need to figure out the Feet of head of your pump. A good estimate is to take the amount of feet from where your suction lines are (skimmers or main drain) back to where your pump will be located. The total amount of return piping should give you a good idea on how many feet of head your pump will have.

Many of the Swimming pool pumps will have charts showing the Horse Power of each pump. These charts are usually shown with the GPM vs. The Feet of Head.

For example, if you have a 20,000 Gallon pool.**GPH = **20,000 / 8 = 2,500**GPM** = 2,500 / 60 = 41.7

Now that you have your GPM, we need to make a couple more assumptions. Let's say you choose the popular Hayward Super Pump and you have found your total return piping to be a total of 30 feet. N ext look at the chart listed on Hayward Super pump description page (see below)

Pump Output (GPM) vs. Total Resistance To Flow (Feet of Head) |
||||||

Model No. Max Rated |
20 ft |
30 ft |
40 ft |
50 ft |
60 ft |
70 ft |

SP2600X5 |
55 |
45 |
29 |
-- |
-- |
-- |

SP2605X7 |
67 |
58 |
47 |
31 |
-- |
-- |

SP2607X10 |
85 |
76 |
65 |
50 |
27 |
-- |

SP2610X15 |
97 |
90 |
80 |
67 |
50 |
10 |

SP2615X20 |
116 |
111 |
99 |
85 |
70 |
51 |

SP2621X25 |
109 |
109 |
104 |
95 |
84 |
69 |

With 30 feet of head and 46.7 GPH we would use the SP2605X7 (always go to the higher size GPH, 58 in the example). The SP2605X7 is a 3/4 HP pump.**The Size of Inground Filters**

The most important factor of the size of the Swimming Pool Filter is the GPM your Pool Pump produces. Filters have a designed flow rate. This designed flow rate should be higher than the size of your GPM your pool pump produces.

In the example above we were using the Hayward Super pump that produces a 58 GPM at 30 feet of Head. If we were to choose the Hayward Star Clear Plus as our chosen filter we would use the chart found on the description page **Performance Data--Residential **

Turnover (In Gallons) | ||||

Model Number | Effective Filtration Area | Design Flow Rate* | 8 Hours | 10 Hours |

C7512 | 75 ft^{2} |
75 GPM | 36,000 | 45,000 |

C9002 | 90 ft^{2} |
90 GPM | 43,200 | 54,000 |

C12002 | 120 ft^{2} |
120 GPM | 57,600 | 72,000 |

C17502 | 175 ft^{2} |
120 GPM | 57,600 | 72,000 |

The size of the filter that could handle the 58 GPM Super Pump would be the C7512.

**Hayward Filters**- Hayward Pump & Filter Systems
- Jandy Filters
- Pentair Pool Filters
- Sta-Rite Pool Filter

**The Size of the Above Ground Pump and Filter System**

The size of your system is mostly determined on the size of your above ground pool. The gallons found inside your pool will give you the horse power needed for your pump. A simple rule to follow is you should be able to clear all of the gallons of your pool in an 8 hour period of time. You can use the following as a guideline.

• Above Ground Pool up to 24 Ft. Round = 1 HP pump

• Above Ground Pool over 24 Ft. Round = 1 ½ HP pump

**Determine the BTU Size for Swimming Pool Heaters**

The Surface area will help determine the BTU size of your pool heater. Decide on the temperature rise you want per hour Then consult this chart. Heat rise will vary slightly when dealing with different heaters. We usually recommend an increase of 1 - 1 1/2 degree per hour.

Pool Size -Square Feet | |||

BTU Size | 500 Sq. Ft. | 650 Sq. Ft | 800 Sq. Ft. |

200 | 1 degree | 1 | - |

250 | 1 1/2 | 1 1/2 | - |

350 | 2 | 1 3/4 | 1 |

400 | 2 1/2 | 2 | 1 1/4 |

- Hayward Heaters - Low Nox
- Pentair Heaters - MasterTemp
- Raypak Heaters - RP Series
- Raypak Heaters - Low Nox
- Raypak Heaters - ASME
- Raypak Heaters - HP Series
- Sta Rite Heaters - Max-E-Therm
- Jandy Legacy Pool Heaters
- Laars Heaters - Lite 2
- Laars Heaters - LXi
- Pool Heater Covers
- Swimming Pool Heat Pump
- H-Series Accessories
- Pool Chillers

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