Pool Pump Buying Guide

The Short Answer

A pool pump is the heart of your pool's circulation system. Get the sizing wrong and you'll either waste money on power or end up with a pump that can't keep your water clean. The right pump depends on your pool's volume, your pipe diameter, your filter type, and how many hours a day you need to run it.

This guide walks through the key decisions in plain terms so you can buy with confidence, or have an informed conversation with your pool specialist.

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Why the Pump Matters

Your pump drives water through the filter, heater, chlorinator, and back into the pool. If it's undersized, water won't turn over often enough and you'll fight algae and cloudy water constantly. If it's oversized, you'll pay more on power than you need to, and you may create pressure problems in your pipework.

Getting the match right between pump, pool size, and system layout is the single most important equipment decision you'll make.

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Step 1, Know Your Pool Volume

Every pump recommendation starts here. You need to know roughly how many litres your pool holds.

A basic estimate:

• Rectangular pool: length × width × average depth × 1,000 (for litres)
• Kidney or freeform shapes: multiply the rectangular estimate by approximately 0.85

If you're unsure, your pool builder's paperwork or a previous service record may have this figure. A pool specialist can also estimate it from your pool's dimensions.

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Step 2, Understand Turnover Rate

Turnover rate is how long it takes your pump to circulate the entire volume of pool water through the filter once.

For most residential pools, the target is to turn the water over at least once every eight hours. In warmer months or with heavier use, twice daily is better.

To work out the flow rate you need:
1. Take your pool volume in litres
2. Divide by the number of hours you want to run the pump
3. The result is the litres per hour (L/h) your pump needs to deliver

For example, a 60,000-litre pool running for eight hours needs a pump capable of at least 7,500 L/h.

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Step 3, Check Your Pipe Diameter and System Resistance

A pump's flow rate is always measured under specific conditions. In a real pool system, resistance from pipes, bends, the filter, and fittings reduces actual flow.

Key points:

• Older pools often have 40mm pipework; newer installs typically use 50mm
• Smaller pipes create more resistance and reduce effective flow
• Longer pipe runs, more bends, and additional equipment (heaters, chlorinators) all add resistance

If you're replacing an existing pump, the safest starting point is to match the flow rate of the pump you're replacing, unless there was a known problem with the original sizing.

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Step 4, Single Speed, Dual Speed, or Variable Speed?

This is one of the most common questions when buying a new pump.

Single Speed Pumps

Dual Speed Pumps

Variable Speed Pumps

For Auckland homeowners running a pump year-round, the energy savings from a variable speed pump can offset the higher purchase price over time. It's worth factoring in your typical daily run hours when comparing options.

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Step 5, Match the Pump to Your Filter Type

Different filter types have different flow requirements.

• Sand filters generally handle a wide range of flow rates well
• Cartridge filters have a maximum flow rate, exceeding it can damage the cartridge and reduce filtration quality
• DE (diatomaceous earth) filters also have rated flow limits

Always check the filter's rated flow range and make sure your pump's output falls within it. A pump that pushes too much water through a cartridge filter too fast is a common and avoidable mistake.

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Step 6, Consider Self-Priming vs Non-Self-Priming

Most above-ground and many in-ground residential pumps are self-priming, they can draw water up from the pool without needing to be manually filled first. This is the standard for most New Zealand residential installations.

Non-self-priming pumps are typically used in situations where the pump sits below the water level (common in some commercial or plant-room setups). For most homeowners, self-priming is the right choice.

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Step 7, Think About Noise

If your pump is close to a living area, bedroom, or neighbouring property, noise matters. Variable speed pumps running at low speeds are generally quieter than single speed pumps running flat out. Check the decibel rating if noise is a concern.

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Step 8, Check Compatibility With Your Existing System

Before buying, confirm:

• Pipe connections: Does the pump's inlet and outlet match your existing pipe diameter? Reducers can be used but add resistance.
• Electrical supply: Most residential pumps run on single-phase 230V supply. Larger pumps may require three-phase. Check with an electrician if you're unsure.
• Automation compatibility: If you have a pool automation system, confirm the pump is compatible before purchasing.

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Common Mistakes When Buying a Pool Pump

• Buying on price alone. A cheap pump that's the wrong size will cost more in power and repairs over time.
• Oversizing to be safe. Bigger isn't always better. An oversized pump can damage filters, create turbulence, and waste power.
• Ignoring the total system. The pump works as part of a system. A new pump won't fix problems caused by a blocked filter, undersized pipes, or air leaks.
• Not checking the warranty. Pump warranties vary. Understand what's covered and for how long before you buy.

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When to Get Professional Advice

If you're replacing a pump on an older pool, or if you're not sure about your pool's volume, pipe sizing, or electrical supply, it's worth getting a professional assessment before you buy. Installing the wrong pump can create problems that cost more to fix than the pump itself.

Sparkling Pools can assess your existing system and advise on the right pump for your setup. They've been working on Auckland pools since 1992 and can help you avoid a costly mismatch.