Quick Answer
Yes, it is possible to put too large of a pump on a pool. The pump needs to be properly matched to the size of the pool and its filtration system. Putting too big of a pump on a pool can lead to issues like:
- Wasting energy and electricity from an oversized motor
- Damaging equipment from too much pressure or flow
- Eroding pool surfaces from an excessively strong water flow
- Creating unsafe conditions or damage from water spraying out
The pump flow rate and horsepower need to align with the pool volume and filter size. A pool professional should evaluate the system and recommend the appropriately sized pump. Bigger is not always better when it comes to pool pumps.
How Do You Size A Pool Pump?
Sizing a pool pump properly involves a few key factors:
- Pool volume – The water capacity of the pool in gallons. Larger pools require more pump output.
- Pump flow rate – Expressed in GPM or gallons per minute. This is the water volume the pump can circulate.
- Filter size – Measured in square feet. The pump flow rate must not exceed the filter’s rated capacity.
- Pool type – Different pool types have different circulation needs. For example, saltwater pools use higher flow rates.
- Equipment – Additional equipment like heaters and cleaners add to the pump’s workload and circulation requirements.
The general rule is that the pump flow rate should turn over the entire pool volume once every 8-12 hours. Higher flow rates may be needed for heated pools or those with large surface areas. Consult a pool sizing calculator or pool professional to properly size the pump.
Signs You Have An Oversized Pool Pump
Some indications that the pool pump may be too large include:
- High energy bills from an overworked motor
- Damage to plumbing from excessive pressure
- Loose, broken, or eroded pool surfaces
- Loud noise and vibration from the pump straining
- Water spraying from around pump connections
- Cavitation noise as air bubbles form in the pump
- Premature failure of the pump motor or seals
If the pump is turning over the entire pool volume in less than 4-6 hours, it is likely oversized for the pool. Consult a pool professional to verify the pump sizing and make any needed adjustments.
Problems Caused by an Oversized Pool Pump
Some specific issues that can occur due to having an oversized pool pump include:
Wasting Electricity
An oversized pump motor draws more electricity to run. This can cost hundreds of extra dollars per year in energy bills compared to a properly sized pump.
Equipment Damage
Excessive water pressure and flow rates strain the pool equipment. Seal failures, eroded impellers, cracked housings, and leaks can result. The filter and plumbing are also under extra stress.
Damage to Pool Surface
High-velocity water flow can erode pool plaster or vinyl surfaces over time. This leads to a worn, fading look and the need for costly resurfacing. Pebbletec and exposed aggregate finishes are especially prone to erosion issues.
Safety Issues
Powerful return jets or damaged plumbing can create a risk for swimmers. Water shooting out under high pressure is a hazard. Loose, broken equipment also poses a safety issue.
Noise and Vibration
An oversized pump may create disruptive noise and vibration while operating. This disturb homeowners and potentially neighboring properties.
Sizing the Pump to the Pool Volume and Filter
The pool pump flow rate should relate appropriately to the water volume and filter size. Some general pump sizing guidelines include:
- 10 GPM per 10,000 gallons of pool volume
- 1 HP for every 20 GPM needed
- Run rate of 1-2 GPM per square foot of filter area
- 8-12 hour turnover for residential pools
- 6 hour turnover or less for commercial pools
There are pool pump sizing calculators online that can help determine the ideal pump output for a specific pool size and equipment setup. A pool industry professional should verify the calculated pump size during installation.
Example Pump Sizing Calculation
For example, for a 20,000 gallon residential pool with a 36 square foot sand filter:
Target circulation rate = 10 GPM per 10,000 gallons
Pool volume = 20,000 gallons
Filter size = 36 sq. ft.
Target pump flow rate = Pool volume x Circulation rate
= 20,000 x 10 GPM / 10,000 gallons
= 20,000 x 0.10
= 2,000 GPM
For a turnover every 12 hours:
Minimum flow rate = Pool volume / Turnover time
= 20,000 gallons / 12 hours
= 1,667 GPM
For the filter size:
Ideally 1-2 GPM per square foot of filter
1 GPM x 36 sq.ft. = 36 GPM
2 GPM x 36 sq.ft. = 72 GPM
Conclusion: A pump sized at 25-50 GPM would be appropriately sized for this example pool. The horsepower would be 1.25 to 2.5 HP based on the 20 GPM per 1 HP sizing rule.
Steps to Match the Pump to the Pool
Here are the key steps pool owners should follow to ensure their pump is right-sized for their pool:
- Calculate the total water volume in gallons – Length x Width x Average Depth x 7.5
- Identify the existing filter size in square feet
- Target an 8-12 hour turnover rate for the water volume
- Select a pump flow rate (GPM) that meets the turnover target
- Choose a pump motor horsepower suitable for the flow rate
- Confirm the flow rate aligns with filter size – 1-2 GPM per square foot is ideal
- Have a pool professional validate the sizing for your pool
- Make any necessary adjustments or replace undersized/oversized pumps
Properly sizing the pump to the pool from the start prevents issues. When in doubt, consult a pool sizing expert.
Can You Install a Bigger Pump on an Existing Pool?
It is possible to install a bigger pump on an existing pool system, but the rest of the equipment must be checked to ensure it can handle the increased flow and pressure. Some key considerations when upgrading pump size include:
- The filter, valves, plumbing must be rated for the higher pump output
- The electrical system may need upgraded wiring and a new circuit for a larger motor
- A larger pump basket or leaf canister may be required to avoid clogs
- The pool shell and surface material should be durable enough to withstand faster water flow
- Check for leaks, cracks, or weak points that could worsen with pressure increases
- Modify return fittings if necessary to avoid powerful jets that could harm swimmers
Ideally, the project should include a full evaluation of the pool hydraulics to ensure everything is sized compatibly with the new pump flow rates. Changing only the pump without addressing the rest of the system can lead to problems.
Signs It May Be Time to Upgrade the Pool Pump
Some signs that an older or undersized pool pump may need upgrading:
- Pump is aging and has had major repairs
- Energy bills for the pump are increasing
- Pump cannot keep up with the pool’s circulation needs
- Water flow is weaker than normal
- Pool does not meet the local health department’s turnover requirements
- Newer equipment has been added like salt chlorinators that need higher flow
- Filter needs frequent backwashing due to poor water flow
- Pool takes a very long time to heat up with the heater
- Algae growth and other water quality issues are increasing
Upgrading to a modern, energy efficient variable speed or multi-speed pump motor can save significant electricity and better meet the pool’s needs.
Cost of An Oversized Pool Pump
The main cost of an oversized pool pump is wasted energy. A pump that is too big will run up the electric bill unnecessarily. Some estimates indicate an oversized pump can cost $100-$500 more per year to run compared to a properly sized pump.
Pump equipment also wears out faster when overworked, leading to shorter service life and earlier replacement costs. Repairing damage from things like leaks or burst pipes caused by excessive pressure can also be expensive fixes.
In some cases, the extra wear on the pump motor may shorten its longevity from 7-10 years down to as little as 2-3 years before failure. Premature pump failure then necessitates an expensive replacement.
Example Pump Replacement Cost
Typical pool pump replacement costs:
| Pump horsepower | Replacement Cost (parts and labor) |
| 1 HP | $400 – $700 |
| 1.5 HP | $600 – $900 |
| 2 HP | $800 – $1,100 |
Higher horsepower or premium pumps for larger pools, water features, or competition pools can cost even more. Avoiding premature pump failure due to improper sizing saves owners the major future expense of replacement.
Energy Use of Properly Sized vs Oversized Pumps
An oversized pool pump uses significantly more electricity. For example:
| 1 HP Pump | 2 HP Pump | |
| Properly Sized | 1,500 kWh/year | 2,500 kWh/year |
| Oversized | 2,000 kWh/year | 3,500+ kWh/year |
At an average electricity rate of $0.12 per kWh, the 2 HP oversized pump would waste over $300 per year in electrical costs compared to an appropriate 1 HP model. And more expensive repairs and shorter service life add to the oversized pump costs.
Pool Pump Sizing Mistakes to Avoid
Some common pool pump sizing errors include:
- Basing pump size only on pool gallons and not factoring in other equipment
- Using pump flow rates that are too high for the filter size
- Not considering a saltwater chlorinator’s flow requirements
- Using high turnover rates intended for commercial pools in residential settings
- Failure to account for hydrostatic pressure on inground pools
- Not confirming flow rates and pressure with a professional
- Assuming that bigger is automatically better
Working with a pool industry pro and following proper sizing methods avoids these mistakes. Don’t size based just on pool volume alone. All aspects of the system design must align.
FAQs – Pool Pump Sizing
Can you put too small of a pump on a pool?
Yes, it is possible to undersize the pump for a pool. This can lead to insufficient water circulation, poor filtration, and trouble maintaining proper chemical balances. However, an undersized pump is generally safer and less expensive than having one that is too large.
How much horsepower do I need for my pool pump?
The ideal pool pump motor horsepower depends on the pool size, equipment, and target flow rate. As a rule of thumb, you need 1 HP for every 20 GPM of needed water circulation. Small pools may only need 3/4 or 1 HP pumps. Large commercial pools may require 5 HP or more.
Can I turn the dial up higher on my variable speed pump for more flow?
You can increase the speed setting, but only do so if the rest of the system is rated to handle greater flow rates. Turning the dial higher on an undersized pump strains the motor. Make sure the filter, plumbing, and equipment can handle the pressures at that pump speed.
Should I get a bigger pump with a new pool?
Not necessarily – bigger doesn’t mean better when sizing a pool pump. Have a qualified pool professional calculate the optimal flow rate and horsepower needed for the new pool’s volume and planned equipment. Stick with that recommended size for a properly balanced system.
Conclusion
Installing too large of a pool pump creates unnecessary expense and risks for equipment damage. It is important to take a holistic approach and size the pump based on the pool volume, filter size, equipment, flow rate needs, and recommended turnovers. While a pump that is too big may seem beneficial, it ultimately wastes energy, erodes surfaces faster, strains the motor, and shortens equipment lifespan. Consulting a pool industry professional ensures the pump is right-sized from the start to avoid issues.