Calculating a Pool Size & Pump

Please remember that water and electricity are a deadly combination and do not mix. Use any of the information contained herein AT YOUR OWN RISK.

We will not be held liable for any injuries that may result from the troubleshooting advice or installation of any electrical components in your hot tub spa unit.

 

Calculating a Pool Size & Pump

Why Pick Us!!

Since 2003 we have sold thousands of pumps of varying shapes and sizes, we offer a fantastic portfolio of swimming pool pumps to suit a variety of specific needs, environments and budgets. If you can't find yours here ring us and we will try and source it for you....

Our extensive portfolio means if you have the details of your existing pump and it has worked admirably in your application then just click the appropriate brands in the domestic pool section and see our competitive pricing and be assured our service leads the industry prior to buying....

Which pump?

Repeat business covers a large proportion of our click-and-buy sales because the layout of your pool piping & the connections points means that for trouble-free replacement most people just replace their existing pool pump with the same model as before.

If however, the old pump was underpowered or you are changing your system slightly or just buying a pump for the first time then you will be going for a different pump. This will mean more work (potentially) in connecting it to the existing setup, this is not beyond the competent DIY'er or your local plumber so don't worry too much we can talk you through it, it just means buying and fitting some new pipe work.

If you are direct replacing then if your existing pump was say 3/4 Horse Power then replace it with the same rating, but if you plan to change your system i.e. solar matting etc then you may well require a more powerful pool pump.

Be aware, that some automatic pool cleaners don't work well with lower-powered swimming pool pumps.

Which Brand?

Due to our years of trading, we have fine-tuned our portfolio to provide a pump for all budgets but one common thread prevails they are all proven, reliable top-end pumps with high-quality components and parts (found on our site) to back up the unit in the years to come.

However each brand has subtle nuances but in lamens / budgetary terms Astral & Sta-Rite are slightly more expensive but have the greatest worldwide track record, slightly less on the pocket but with similar quality assurances is Certikin's range of swimming pool pumps.

Plastica's Argonaut / Mega-Pumps and the Hayward range offer some of the lowest prices in the marketplace but still retain a fantastic reputation.

Sizing A Pump

Before we begin, please feel free to contact us for a free consultation when buying either a new pump or replacing an existing unit if the below is too confusing...

Over the years we have noticed our customers always want to purchase a bigger pump than is actually necessary because we all know bigger is better (LOL). What happens then (if they did) is firstly higher operating costs, but more worrying they may well be overpowering their filtration system.

So the general rule of thumb is your pump should filter all the water in your swimming pool in an 8-hour period, so, this page shows you how to select a pump that turns all the water over in your pool in 8 hours

Horse Power is not important at the moment but more importantly the amount of water the pool pump moves in an hour. Pipe resistance directly affects this amount.pipe resistance is measured in "metres of head".

To work out the resistance is complicated!!

Most customer pools have a resistance of between 10 - 13 metres. As a general rule of thumb, you should circulate your entire pool volume in 8 hours, so your hourly capacity should be the volume of your pool divided by 8.

So, for example, if you have a 40ft x 14ft pool at an average of 4ft depth, our calculator tells us the volume is approx. 64 cubic metres.

Next, divide 64 by 8 and hey presto you get 8m3 per hour required.

So you need to choose a pool pump with a capacity greater than 8m3 per hour. Typically a 0.75 Horse Power pump is the one you need

So the first step is to determine the amount of water in your pool. The formulas for calculating this depend on the shape of your pool....so lets look at the different shapes

What to do with different depths..

To determine average depth add the depth at the shallow end to the depth at the deep end and divide by two.

Simple Rectangular Pool  
metres   feet
Enter dimensions of pool Metres   Feet Inches   Volume of water
Length (L):     cu metres:
Width (W):     litres:
Minimum Depth (D1):     imp gallons:
Maximum Depth (D2):     us gallons:
(If the pool has a flat bottom,
enter the same figure for max and min depth.)

 

 

Circular Pool  
metres   feet
Dimensions of pool Metres   Feet Inches   Volume of water
Diameter (d):     cu metres:
Minimum Depth (D1):     litres:
Maximum Depth (D2):     imp gallons:
            us gallons:
(If the pool has a flat bottom,
enter the same figure for max and min depth.)

 

 

Eliptical Pool  
metres   feet
Enter dimensions of pool Metres   Feet Inches   Volume of water
Major Diameter (a):     cu metres:
Minor Diameter (b):     litres:
Minimum Depth (D1):     imp gallons:
Maximum Depth: (D2)     us gallons:
(If the pool has a flat bottom,
enter the same figure for max and min depth.)

 

 

Irregular Pool  
metres   feet
Enter dimensions of pool Metres   Feet Inches   Volume of water
Area (A):       cu metres:
Depth (D):     litres:
            imp gallons:
            us gallons:
(If you have several depths,
break up your area calculation for each depth.)

For irregular shapes, calculating the area is less accurate. You will need to draw up the pool accurately to scale on graph paper using a square on the paper to represent a metre (or foot) square of pool. When you have finished, count the squares. For partial squares, count anything over half as one and ignore any under a half. When you have the area (A) multiply by depth (D) for the Volume in cubic metres. If you have several depths, break up your area calculation for each depth.
 

Overview

You now have all the information required to select the size of your pool pump so if you have an idea of your budget, have a good look around at the makes we have highlighted - or info@poolandspacentre.co.uk to discuss your needs

Each pump description page, provides a chart showing the HP required for your Metres of Head.

An important note to mention is the size of your pool filter is directly related to the pool pump you select, so if your pool filter is too small for the pump, there will be strain on the pumps motor to push water through as it encounters resistance at the filter., eventually leading to pump failure and your filtration may also be compromised.

We always recommend selecting an oversized filter to be certain it can handle the flow coming from the pump.

Other Considerations

The calculations are based on basic pool configuration with no extra water features like: fountains, spas, waterfalls, solar heating, and in-floor cleaning systems. These features generally require higher HP pumps.

Also pools with these features typically need at least 2" diameter suction pipes as suction pipes of 1 1/2" have a lower physical limit.

 

 

 

Categories: Pool Pumps
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