How to Choose the Right Pool Pump Size

A pool pump is the heart of your pool's circulation system. It pulls water from the pool, pushes it through a filter, and returns it back clean. Choosing the right size pump is crucial for keeping the water clean without wasting energy or damaging equipment.

If your pump is too small, it won't circulate the water efficiently. If it's too large, it can lead to high electricity bills and unnecessary wear on your plumbing.

Key Terms to Know Before Choosing

Before picking a pump, you should be familiar with a few important terms:

• Horsepower (HP): Measures the pump’s power. Higher HP moves more water but also uses more energy.

• Flow Rate (GPM): Gallons per minute. It tells you how much water the pump can move.

• Turnover Rate: The time it takes for the pump to circulate all the water in the pool once.

• Total Dynamic Head (TDH): The resistance in your pool’s plumbing system that the pump must overcome.

Step 1: Calculate Your Pool Volume

To determine the right pump size, start by calculating the total volume of your pool in gallons. Here’s a quick guide based on shape:

For Rectangular Pools:

Length x Width x Average Depth x 7.5 = Pool Volume

For Round Pools:

Diameter x Diameter x Average Depth x 5.9 = Pool Volume

For Oval Pools:

Length x Width x Average Depth x 6.7 = Pool Volume

Step 2: Determine the Desired Turnover Rate

A good pump should be able to circulate all of your pool water at least once every 8 hours. Use this formula:

Pool Volume ÷ 8 = Gallons per Hour (GPH)

Then, convert GPH to GPM:

GPH ÷ 60 = Gallons per Minute (GPM)

This GPM is the flow rate you need your pump to deliver.

Step 3: Consider the Resistance in Your Plumbing

Your pool's plumbing layout adds resistance to water flow. This is measured in feet of head or Total Dynamic Head (TDH).

Factors that increase TDH:

• Long or complex pipe runs

• Elevation changes between the pool and pump

• Multiple fittings, elbows, or valves

• Features like waterfalls, heaters, or in-floor cleaning systems

Most residential pools fall between 30 to 50 feet of TDH. Check the pump's performance chart to see which models meet your flow rate at your estimated TDH.

Step 4: Choose the Right Pump Type

There are different types of pool pumps to consider:

Single-Speed Pumps

• Run at one speed only

• Least expensive upfront

• Highest long-term energy cost

Dual-Speed Pumps

• Can run at high or low speeds

• Good for energy savings during light filtration

Variable-Speed Pumps

• Can be adjusted to different speeds

• Most energy-efficient

• Higher upfront cost, but lower operating cost

Variable-speed pumps are often the best long-term choice because they reduce energy bills and extend the life of pool equipment.

Step 5: Match the Pump to Your Filter

Your pump and filter should work together. If the pump pushes more water than the filter can handle, it can damage the filter or lead to poor filtration.

Check your filter's flow rate rating and make sure your pump doesn't exceed that rate. Oversized pumps can overpower small filters, causing pressure buildup.

Step 6: Account for Pool Features

Do you have any extras like a spa, waterfall, or solar heater? These features increase the demand on your pump.

Add-ons that require extra pump power:

• Pool heaters

• Water features

• Attached hot tubs

• In-floor cleaning systems

If you have these, consider upgrading to a pump with a higher flow rate or a variable-speed model for flexibility.

Common Mistakes to Avoid

• Choosing a pump based on horsepower alone: Always match flow rate to your pool's needs, not just HP.

• Ignoring TDH: Not accounting for resistance can lead to buying a pump that underperforms.

• Oversizing the pump: Bigger is not always better. It wastes energy and may wear out equipment faster.

• Not checking local codes: Some areas require energy-efficient models. Always check regulations before buying.

Final Tips for Choosing Your Pool Pump

• Measure your pool accurately before calculating flow needs.

• Aim for a turnover rate of once every 8 hours.

• Use manufacturer pump charts to match GPM to TDH.

• Invest in a variable-speed pump if budget allows.

• Ensure your filter and plumbing system can handle the pump’s output.

By following these steps, you’ll avoid costly mistakes and get the right pump that keeps your pool clean, clear, and energy-efficient.