How to Size a Sump Pump

Last Updated on by Anthony Brown

Picking the right size sump pump is important, pick too powerful of a pump can result in the motor burning out while too weak of a motor can cause your basin to flood during heavy rains. In this article we will help you answer the age old question – what size sump pump do i need? Keep reading to learn how to size a sump pump get the the right size for your home.

Choosing the right horsepower and pump should not be as difficult and confusing as it sounds – and it is important to remember that bigger is not always better when it comes to sump pumps. Some of the most important factors to consider when picking the right size sump pump are the head height, max flow rate and discharge line sizes.

Not sure what all this means – keep reading to learn more from our team of experts so you don’t buy a pump that is too powerful or too weak.

Sump Pump Sizing Chart

Use our sizing chart to help pick the right pump if you already know information like head height and max gallons per hour.

Sump Pump Sizing Calculator

If you know your head height, discharge pipe distance or gallons per hour you can use our calculator to pick to right horsepower motor.

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How to Size a Sump Pump

Accurately sizing a sump pump can be difficult for new homeowners and a lot is on the line. If you pick a model with a motor that is too weak it won’t be able to push water out of the basement. On the other hand, if you choose a motor that is too powerful it can drain the basin too fast and burn out the motor.

The best way to get the correct size is to measure the horizontal and vertical distance then estimate the gallons of water per hour the pump will need to drain. Once you have this information you can multiply the gallons per hour X 1.5 X 60 to find the total gallons per hour.

1/3 vs 1/2 HP Sump Pump

The two most common sized motors are 1/3 and 1/2 HP sump pump. If you are shopping for a new pump and comparing 1/3 vs 1/2 HP pump there are a few things to keep in mind – both sizes have pro’s and con’s!

1/3 HP Pumps

1/3 horsepower pumps are good choices for low head heights and flow rates under 1,300 gallons per hour. They use less power and makes less noise than a 1/2 HP pump but they may not be able to pump enough water in high flow rate areas.

1/2 HP Pumps

1/2 horsepower sump pumps are a good pick if you need a pump that can handle large amounts of water and pump it up large vertical head heights. The only downside to keep in mind is that if the motor is too powerful it may burn out early.

Common Factors that Affect Sizing

There are a number of factors that go into determining the correct size sump pump. The most important factors to consider are the horizontal and vertical distance the motor will need to push the water. The more piping – especially vertical – in your drain system the more powerful and higher horsepower pump you will need.

Vertical Piping
Vertical drain lines require a more powerful pump because they are working against the forces of gravity. The higher the head height the higher horsepower motor needed. If the pump does not have enough power it will not be able to push water up and out of the basement and could cause a flood.

Horizontal Piping
Horizontal piping requires less power from the pump to push the water. Friction and distance of discharge pipes both play an important role in determining the size of the pump. Horizontal piping may be required to remove water from your basement but a well thought out design can minimize piping.

Frequently Asked Questions

What is the best size sump pump?
There is no one best size when it comes to sump pumps. Each situation and budget is different – meaning you may need to do some extra research in order to get the best pump for your home.