What Size Sump Pump Do You Need?

choosing the right sized sump pump
Like much of the plumbing and machinery in your home, you may not think about your sump pump most of the year. However, when there is a heavy rainfall or snow melt here in Montana, the sump pump in your home becomes vital to ensure you will not be standing in ankle-deep water, or up to your neck in water damage repair bills. But how do you know which sump pump is right for your home, and which size sump pump you need? Learn more about sump pumps here, including what they are and what size sump pump you will need in your home. 

What Is A Sump Pump? 

The sump pump in your home is a submersible device installed in the lowest part of your home, usually in the basement or crawl space. It may be small, but it is an important part of your home that keeps the basement from flooding

Most of the time, especially during warm, sunny weather, the pump is not working, simply on standby until it is needed. However, when it rains heavily or snow close to the home begins to melt, the soil around the base of your home will become oversaturated with water. This excessive groundwater funnels toward the sump pump in the low pit it sits in. This activates the pump, which begins to pump water out of the home. Excess water is then funneled into a nearby storm drain, dry well or pond. This prevents the water from rising in your home! 

How To Tell If You Need A Sump Pump

Where you live says a lot about whether you will need a sump pump in your home. Some properties will need these devices more than others. Here are some scenarios where you will need a sump pump:
– You live in a place that receives heavy rain or snow (yes, that is us here in Montana!)
– Your home is built in a flood-prone area
– You have had flooding or water problems in the past
– Your basement is finished

Why Does Your Sump Pump Need To Be The Right Size?

Isn’t there a saying that “bigger is better?” With sump pumps, this is not always the case. An oversized sump pump can lead to constant cycling, which will cause your system to burnout prematurely. An undersized pump can lead to the same issue or may not be able to handle the water in your home. It is important to choose a sump pump that is the right size for your home and sump pit. 

What Size Sump Pump Do I Need For My Home? 

There are several factors you will need to take into consideration when choosing the size of your sump pump, including capacity, motor power and the size of your sump pit, or the hole where the sump pump sits. 


Your sump pump needs to be able to pump out the water that gathers in the sump pit before the pit overflows, so the capacity of the pit has to match the pumping capacity of the sump pump. If you are not sure if your current sump pump has the proper capacity, you can easily check. On a moderately rainy day, run your sump pump until water recedes to the shutoff level. Once the water is low enough, turn off or unplug your pump, and leave it off for one minute. Do not leave it off any longer than one minute! During this time, measure how far the water rises during that time. You can multiply this by 60 to see how much water would fill the sump pit over an hour. This will allow you to estimate the volume of water your home receives in an hour, and check if the capacity matches that of your sump pump’s abilities. 

Note – you may want to multiply that final figure by 1.5 to build in a safety factor for pumping capacity. This way, your pump will be ready for extra rainy days or winter snow melts. 

Motor Power: 

The horsepower of the motor states how powerful the sump pump’s motor is. Sump pumps are generally standard at .33 horsepower, but they can also be .25 horsepower, .5 horsepower (1/2 horsepower) or even ¾ horsepower. If you live in an area that is at a higher risk for floods, you may want a higher horsepower motor. 

Sump Pit Size And Other Factors: 

If your sump pit size is wider than standard, it may hold more water. Additionally, if the water must move farther through the discharge pipe, for instance, to a drain half a block away instead of right outside your home, the pump may have to take longer to push the water out. 

Central Heating, Cooling, Plumbing & Electric

If you are concerned your sump pump is the wrong size or need a new sump pump for your home, your best bet is to contact a professional plumber, who can evaluate the situation for you. Contact the team at Central Heating, Cooling, Plumbing and Electric here in Kalispell, Montana, for more information.

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