What Size Pump Do I Need For My Pool?

A common question we get from our customers is “What size pump do I need for my pool?” As a general rule, you should choose a pool pump that filters all water in your pool in an eight hour period. It’s important that you don’t buy a pump bigger than your pool needs because it leads to higher operating costs and overpowering your filter system.

The standard hours a pool pump should take for total water circulation (turnover time) varies. The following turnover times for residential pools are accepted in the pool industry:

• Indoor pools – 4 hours

• Outdoor pools – 6 hours

Step 1: CALCULATE THE NUMBER OF LITRES IN YOUR POOL

Here’s an easy example of calculating your pool volume:

Length 10 m x Width 4 m x Average Depth 1.4 m = 56,000 litres

Step 2: CALCULATE THE FLOW RATE

Flow rate how many litres the pump moves per minute (lpm). This is calculated using both the pool’s volume and turnover time.

Turnover time is the time it takes for a volume of water equivalent to that of the pool contents to make one pass through the circulation system. 

The following turnover time is accepted in the pool industry under residential pools. 

- Indoor Pools - 4 hours

- Outdoor Pools - 6 hours

So let’s say you have an indoor 56,000 litres pool and a pump that has a turnover time of 4 hours, you can then work out the flow rate of your pump. For example:

Turnover time = 4 hours x 60 minutes = 240 minutes

Flow rate = Divide the volume (56,000 litres) by the turnover time (240 minutes) = 230 litres per minute. 

Step 3: CALCULATE THE TOTAL DYNAMIC HEAD

Now that we have the flow rate (230 lpm), we need to calculate the TDH (Total Dynamic Head) in metres to determine the performance of the pump needed to turn over the water. TDH refers to the total equivalent height that fluid will be pumped by taking into consideration any friction losses in the pipe. Essentially “dynamic head” is the measurement of resistance working against your pool pump as it pulls water from your basin and pushes it back to the pool. Most inground pools will be somewhere around 15 metres TDH. Above ground pools typically fall around 9 metres TDH.

For example:

Head Loss - Pipe (m) = 3.80 + Head Loss - Valves & Fittings (m) = 6.20 = 10 Total Dynamic Head (m)

Now that you know the Total Dynamic Head (10 m) and the flow rate (230 lpm), you can use this information to find the size of pump you will need to efficiently turn over your pool.

Step 4: REFER TO THE FLOW CHART

By using the numbers we have calculated above (Flow Rate 230 lpm and 10 m Total Dynamic Head) and this flow chart, you will arrive at the conclusion that CTX 280 pump would be the suitable size.

Note: Flow charts can be found in Resources > Brochure on the pool pump pages. 

Step 5: FIND THE RIGHT SIZE FILTER

Now that you have found the appropriate pump size for your pool, you will need to find the correct pool filter size to match. If we continue with the CTX280 pump example, based on its input of 1070 W, we should select a 25" or 28" filter to go with it.

See below for other examples:

• 500 W goes with 20″ filter

• 750 W can go with 24″ filter

• 750 and 1100 W can go with 25 and 28″ filter

• 1100 and 1800 W can go with 28″ filter

• 1800 and 2000 W can go with 33″ filter

Source: Fiberglass Media Filter Resources > Manual

Find out more about the detailed calculations here or get in contact with one of our specialists if you need further assistance in your search for the right pool pump for your swimming pool.