Pool Pump Size Calculator Australia - What Size Do I Need For My Pool?

Thinking about getting a new pump but confused about what size is right for your swimming pool?

This pool pump size calculator will help you quickly size a pump for your pool, avoiding the common problem of an undersized or oversized pump.

Why Calculate Pool Pump Size?

Calculating your pool pump size is essential for ensuring that you select the right pump for your pool.

Undersized pumps won't be able to circulate the water in your pool well, resulting in poorly-mixed dead zones and inadequate dispersal of pool chemicals like chlorine.

Over time, you may start to see algae growing in the corners of your pool, where the water is poorly mixed and chlorine levels are low.

On the other hand, oversized pumps will use more electricity than necessary, costing you money. An oversized pump might also put out a flow too big for your filter, putting strain on it and shortening its lifespan.

However, calculating the right size for your setup is not difficult, thanks to this useful pool pump size calculator.

Note: If you haven't sized your filter yet, check out this pool filter size calculator.

How Do I Calculate Pool Pump Size?

To correctly size your pool pump, you need to know 2 important pieces of information:

• Pump flow rate
• Total dynamic head

Pump Flow Rate

The ideal pump flow rate for a particular pool is typically calculated based on the concept of turnover. One turnover is when the equivalent of one full volume of pool water passes through the pump.

It is generally recommended that pumps are sized to turnover the contents of the pool within a certain period of time.

This is about 4 hours for indoor pools and 6 hours for outdoor pools, although this can be extended out to about 8 hours for outdoor residential pools, as long as you are happy with running your pump for a longer period of time each day.

The pump flow rate is expressed in litres per minute (LPM) and calculated by dividing the pool volume by the turnover time.

For a 50,000L pool with a turnover time of 6 hours, the calculation would be:

Pump Flow Rate = 60,000 L / (6 hours x 60 minutes / hour)
Pump Flow Rate = 60,000 L / 360 minutes = 167 LPM

Total Dynamic Head

The total dynamic head is a measure of the amount of resistance that a pump will have to overcome to pump water out of your pool.

It is calculated from the following factors:

• Pipe Head Loss
• Fittings Head Loss
• Elevation Head Loss

The pipe head loss is a measure of the friction in the pipe from the pool to the pump. The longer and narrower this pipe is, the greater the pipe head loss, and the more resistance there is for the pump.

The fittings head loss is a measure of the resistance caused by the bends, valves and other fittings in the pipework. The more fittings, the greater the head loss.

Finally, the elevation head loss is simply the change in elevation from the pool surface to the pump intake. The higher the pump is above the pool water level, the greater the resistance and therefore the greater the head loss.

You can read about each of these factors in detail over at this total dynamic head calculator.

What Size Pump Do I Need For A 50,000L pool?

As we've just discussed, pool volume isn't the only factor when it comes to calculating pump size. However, we can make some assumptions to calculate the necessary pump size.

For a pool volume of 50,000L and a turnover time of 6 hours, the ideal pump flow rate would be:

Pump Flow Rate = 50,000 L / 360 minutes = 139 LPM

The total dynamic head would vary from pool to pool, but we can make some assumptions. If the pool had 8 metres of 25mm pipework from pool to pump, the pipe head loss would be 6.66m. Note that this was calculated using the TDH calculator.

If there were 6 x 90° bends and 1 ball valve in the line, the fittings head loss would be 1.01m.

Finally, if the pump intake was 1 metre about the pool water level, there would be 1m of elevation head loss.

Summing these up give us 9.76m of total dynamic head. We can round this up to 10 metres for simplicity.

Looking at pump charts for the AstralPool CTX, Onga Leisuretime and Davey PowerMaster ranges, lets us know that any of these three pumps would be suitable for our pool:

• AstralPool CTX 280
• Onga Leisuretime LTP550
• Davey PowerMaster PM200

Note that the CTX 280 and the PM200 are probably oversized for this pool, but they are the smallest pumps in their respective range. In this case, the LTP550 best matches our pool and is probably the one that we would go with.

If sizing a pool heat pump, check out this calculator.