Updated April 13, 2023
A sump pump is a device that reduces the risk of water damage to the underground part of a home. When there’s excess water in the ground around your basement (for example, from rain or spring snowmelt), a sump pump moves that water up and away from the building. Installing a sump pump often helps you save money on your insurance premiums, too.
If your home sits in a high-risk area, chances are you already have a sump pump. But where should you look if you’re unsure? And, if you’re considering installing a sump pump, how do you figure out the right power and capacity? Here’s your ultimate guide to home sump pumps:
A sump is a low space that collects liquids. Your car, for instance, has a sump to collect oil. In the same way, homes have a small pit that’s dug into the floor of the basement to collect water that filters through the loose earth surrounding your foundation.
A sump pump is a simple device that detects water in the sump and moves it away from the property through a network of pipes. Check out this video for a simple explanation of how a sump pump works.
Sumps are usually 2 feet deep and 18 inches in diameter. When the water rises to a certain level, a floating switch completes an electrical circuit and engages the pump. Systems usually contain a one-way check valve which prevents expelled water from flowing back into the pit.
Many sump systems have alarms to alert the homeowner if water rises past a certain point, indicating that the sump pump is failing. Modern smart pump alarms can even send alerts right to your phone. There are also sump pump alarms that indicate the backup pump has engaged, meaning you should check the primary pump (more on primary and backup sump pumps further down).
Sump pumps require electricity. Since they’re operating near (or in) water, it’s important that the outlet you connect the pump to has a ground fault circuit interrupter (GFCI). You should also connect your sump pump to a back-up power source. Flooding often accompanies severe storms, which often cause power failures. If your sump pump detects water but has no power to operate, it’s going to have a hard time protecting you from water damage.
Sump pumps are either primary or backup, and your system should have one of each. Primary sump pumps do most of the work most of the time. The backup sump pump is only there to tag in if the primary pump fails, or if it can’t keep up to the water inflow.
There are two main types of sump pumps: submersible and pedestal. Either type can come in primary or backup variety. You can also divide backup sump pumps based on their backup power source: battery or water.
Submersible sump pumps are bulky devices. They sit right inside the sump pit, and function while underwater (hence, submersible). Since they sit in a pit, they run quieter than pedestal pumps, but are usually more expensive. They’re also harder to access for maintenance.
Pedestal pumps are long, upright devices with the pump motor sitting on top and the intake device, or impeller, at the bottom. The motor on a pedestal pump isn’t meant to get wet. These are less expensive and easier to access for repairs compared to the submersible variety, but some plumbing experts consider them less reliable than submersible pumps. They’re also louder, as the motor sits above the sump pit.
The most common type of backup sump pump is the battery-powered backup. These don’t replace a primary pump. Instead, they spring to life when the primary pump cuts out due to a power failure or some other reason. Most often, they’re connected to a large battery (like a marine or car battery).
Water powered backup sump pumps aren’t connected to an electrical current; they’re powered by good, old-fashioned water pressure. They have the advantage of unlimited runtime, but there are some restrictions. Water-powered pumps need a strong, steady flow of water, like the high-pressure flow of a city water system. In a home with low water pressure, or pump-powered well sources, water-powered sump pumps won’t work correctly. They’re also more challenging to install than their battery-powered counterparts.
It’s also possible to buy an all-in-one sump pump that includes a primary pump and a backup pump in the same package. It may be more cost-effective than buying each separately, but they tend to be large and may not fit in smaller sump pits.
Sump pumps come in a variety of outputs. Each pump comes labelled with a reference chart explaining how much water it can displace.
The chart contains two columns: head refers to the vertical distance that water must travel from your sump pump to the outlet pipe, and flow refers to the volume of water that the pump can displace (in gallons per minute).
These figures are inversely proportional; for any given pump, the flow reduces as the head increases. That’s because the pump must work harder to push the water further up, thus decreasing its efficiency.
To figure out your flow rate, wait for a rainy day and run your pump until the water drops below the shut off level. Then, disconnect the pump from all power sources and measure the distance the water rises in one minute. For an 18-inch sump, one inch of water is equal to one gallon. In a 24-inch sump, one inch of water is equal to two gallons. Once you’ve calculated the flow rate, multiply it by 1.5 to allow a margin for severe storms.
Next, measure the vertical distance from the bottom of your basement to the outlet pipe. The outlet is usually at or around ground level. Then, reference the chart on your pump to see if the flow rate is sufficient for the head distance.
Experts recommend a power rating of 1/3 horsepower for average homes. Take into account elbow joints, narrow pipes and check valves as well; these increase friction, potentially requiring a more powerful pump. If you’re in any doubt, contact a plumber to determine whether your sump pump is sufficient.
A brand-new sump pump, on its own, runs between $100 and $500. Of course, that depends on the size and style; pedestal pumps are much cheaper than combination pumps, for example.
When you buy a new sump pump, the cost of the pump is just one piece of the puzzle—you also need to install it. If you don’t already have a sump pit in your basement, installation can be pricey. Expect to pay at least $2,500-5,000 to dig a new sump pit and install a pump if you’ve got a concrete basement floor.
If you already have a sump pit and you’re simply replacing the pump, the cost is much lower. If you’re comfortable doing the installation yourself, you won’t need to spend more than the price of a new pump, between $100 and $500.
If you have someone install your replacement sump pump, the average cost is around $500, including the price of an average pump.
Finally, be aware of the life expectancy of your sump pump. Most pumps last around 10 years, but the lifespan is affected by the acidity and cleanliness of the water entering the pump.
Sump pumps require scheduled maintenance. Dirt, sand, and other debris can clog the pump and prevent it from working at capacity during an emergency. Most homeowners only find out that their pump isn’t working when it’s too late; we recommend servicing your sump pump every 6 months.
The good news is:
If you’re handy, you can do most of the maintenance yourself. Check out Spruce.com for a simple guide or follow these steps:
If DIY isn’t your thing, call a professional to service your pump. They’ll ensure the pump is working at capacity and test the backup power source and alarm. They’ll also check the discharge line for clogging.
As well, consider installing a backwater valve to prevent your sewer line from backing up into your house. It’s also a good idea to remove debris from any drains, both inside your home and the municipal storm drains nearby.
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As long as they have a back-up power source, sump pumps are fairly reliable. Here are some of the things to watch out for:
Sump pits can fill up with debris, especially open pits without a covering. If too much dirt or debris gets into the pump itself, the system will not operate properly, and may even shut down completely. If a debris-covered switch gets stuck in the ON position, the motor can burn out, potentially causing a fire.
Most sump pump systems have an air gap. The air gap is a section of the discharge pipe that’s open, to allow water to escape the system if the pipes freeze or clog. Normally, the air gap is located where the discharge pipe exits the building.
The air gap may not be literal gap; it may be a slotted pipe or have a vented cover, or one of many possible forms including atrium, candy cane, pipe-in-pipe, and others.
Depending on which type of air gap your sump pump uses, it may be susceptible to getting clogged. You should periodically inspect your air gap while the sump pump is running to ensure that water is flowing through it freely.
If your pump’s flow rating is inadequate, it could struggle to displace all the water entering your home and burn out the motor.
Water that’s expelled from the sump pump usually travels 6-10 vertical feet to exit your house—quite a lot of work for a small pump. Any problems with your check valves will increase the back pressure on the pump, putting it under additional strain.
Sewer systems are not designed to handle large volumes of runoff resulting from heavy rain or snowmelt. If your home’s sump pump is connected to the sewer, it could overload of the system, causing a water backup. This connection also provides an additional point of ingress for water. Consider consider disconnecting your pump from the sewer system (with input from a professional if you need to design a new outflow path).
If your sump pump’s float switch is stuck on, the pump will run continuously when it doesn’t need to. A stuck float switch may simply be stuck. First, check the switch to see if there’s any debris jamming it. Clear the debris and see if it starts working properly.
Alternatively, float switches sometimes get stuck if the pump has wandered out of its original position. As they run, sump pumps vibrate, and may move themselves far enough that the float switch starts getting stuck on something. To fix this issue, reset and re-level your sump pump into the right position.
There are several possible reasons that your sump pump isn’t turning on:
Water damage accounts for more home insurance claims than fire and theft combined. In fact, the average cost of a flooded basement insurance claim is $43,000. As such, it’s likely that your home insurance provider will want to know whether your home has a sump pump and a back-up power system.
If you live in an area that’s at risk of flooding, your home insurance provider may require a sump pump before they’re willing to provide coverage. Insurers often impose higher flood deductibles for homes in high-flood-risk areas as well.
At Square One, we don’t necessarily require that your home have a sump pump. However, in higher-risk areas, customers with battery-backed-up sump pumps are eligible for lower premiums. To get a quote on your own home insurance, click the button at the bottom of this page.
If your sump pump fails and causes your home to suffer water damage, your home insurance will only cover the resulting water damage if it normally covers that type of loss. This depends on how the water gets into your home.
In one example, if your sump pump fails during a rainstorm, allowing groundwater to back up through the sump and into your basement, your home insurance would only cover the loss if it normally covers losses caused by the backing up of sewer, septic and sump systems. Most home insurance policies exclude this kind of loss by default, and would require the purchase of an optional Sewer Backup endorsement that includes sump pump backups.
In another example, if your sump pump were to fail during an overland flooding event – like a river that overflows its banks – many home insurance policies would not respond to this kind of damage at all, whether or not the sump pump is functioning properly.
Some home insurance providers offer overland flooding coverage as an optional endorsement. Square One includes overland flood coverage on most of the policies we sell.
In any home that has a basement, or any part of the house located below-grade (that’s most buildings in Canada), a sump pump is never a bad idea.
If your basement has ever flooded in the past, you absolutely need a sump pump.
If you live in a flat or low-lying area, or somewhere that gets a lot of snow or rain, you should have a sump pump.
If you discover moisture in your basement, dry it out with a dehumidifier and check back a few days later. If the moisture has returned, you probably need a sump pump.
Sump pumps are relatively inexpensive (especially compared to the cost of repairing water damage), so most homeowners with a basement should consider adding a sump pump if they don’t already have one.
How often a sump pump runs depends on its local conditions. Some basements are closer to the water table than others, and so their sump pumps run more often. As well, your property’s grading might cause the sump pump to run even during light rain.
Following heavy periods of rain, it’s common for a sump pump to run intermittently for several days.
If you think your sump pump is running too often, or it suddenly started running more often than you’re used to, there may be something wrong. Here are some potential causes:
Having a battery backup sump pump is important. They work by automatically coming on as soon as the main pump stops working or can’t keep up with the rate of water inflow.
The backup isn’t just a battery connected to the main pump—it’s a totally separate pump. Though, you can buy combination sump pumps that have both a primary and a backup pump in the same unit.
Most models of backup pump will run occasionally just to check that they’re still functioning. If they aren’t, they’ll sound an alarm to let you know. If you find that your backup pump (or your main pump for that matter) isn’t working, fix the problem as soon as possible.
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