Sump Pumps | How They Work, Types, and More

What is a sump pump?

A sump pump is a device that moves water out of a basement and away from the property through a network of pipes.

It’s called a “sump pump” because it’s installed in a sump pit. A sump pit 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.

How sump pumps work

Sumps are usually 60 centimetres (2 feet) deep and 45 centimeters (18 inches) in diameter. The sump pump sits in this pit. The pump is usually not running. When the water rises to a certain level within the sump, it engages the pump’s float switch. The float switch is basically a balloon attached to the on/off switch. The water causes the float to rise, which switches on the pump. Many systems have a sump pump cover to prevent dirt and debris from clogging up the pit.

Sump pump systems should have a check valve. A check valve prevents expelled water from flowing back into the pit if the pump shuts off. Check valves are a crucial part of the system — make sure you have one on your pump. They’re usually located right at the point where the discharge pipe leaves the pump unit.

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 operate near (or in) water, the outlet you connect the pump to must have 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.

Types of sump pumps

The main way to divide types of sump pump is between primary pumps and backup pumps. Your system should have one of each type. 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.

Beyond that distinction, there are other ways to categorize types of sump pumps. Another is submersible vs. pedestal pumps — these can come in primary or backup variety. You can also divide backup sump pumps based on their backup power source: battery backup or water backup.

Submersible pumps

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

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.

Battery-operated backup

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

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.

Combination sump pump

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.

Mini sump pump

You may encounter the term “mini sump pump.” These are simply small sump pumps intended for light usage. If your home needs a sump pump, it’s better to have one that’s too big than too small.

Outdoor sump pumps

Outdoor sump pumps function just like their indoor counterparts. However, they’re used to move water that collects in the yard and move it further away from the foundation. Some properties benefit from supplementary outdoor sump pumps, but they’re not a replacement for the indoor version.

What size pump do I need?

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.

Determine flow rate

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.

Measure

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.

Buying a sump pump

Now that you know how to figure out what size sump pump you need, purchasing one will be simple. But how do you pick the perfect primary and backup pumps for your home?

There are a few important things to keep in mind:

Your new sump pump needs to have enough power to actually move the water out of your home. That includes both the primary and backup pumps.
The new pump is going to have to fit in your sump. If you don’t have much room, you might not be able to fit a submerisible or combination sump pump, for example. If you’re having trouble finding an adequate pump that fits where it needs to, consider expanding your sump pit.
Make sure that your backup sump pump is going to work in case of an emergency. Water powered sump pumps only function if there’s adequate pressure in your water supply. If you don’t have that, you’ll need a battery backup.

Sturdy materials are certainly something to look for when you’re looking for sump pumps. The best sump pumps have cast iron cores, rather than plastic. You can also think about a pump with smart features, like the ability to connect to home WiFi and send you diagnostic information. A smaller consideration is noise. Pedestal pumps tend to make a lot more noise than their submersible counterparts. While noise is a small price to pay for avoiding water damage, you might want a submersible pump just because it’s quieter.

If you’re in doubt about which sump pump to buy, consult with a professional. You don’t want to wait for the water to start rising before you realize your pump’s not powerful enough.

Sump pump costs

A brand-new sump pump, on its own, runs between $200 and $600. 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.

Sump pump replacement

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 $200 and $600.

If you have someone install your replacement sump pump, the average cost is around $500, including the price of an average pump.

Sump pump maintenance

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. Here are the steps to follow for basic sump pump maintenance:

First things first, make sure the pump is upright. The vibration of the motor often causes pumps to shift. If the pump is not sitting straight, the float arm can become jammed.
Check the GFCI outlet to make sure it’s plugged in and the cord is in good condition. If there is moisture present, the GFCI breaker may trip, causing the sump pump to shut down. If so, you’ll need to reset it.
Pour some water into the pit to test the pump. It should start automatically and drain the water away quickly. If not, have it serviced by a professional. While you’re testing the pump, go outside and make sure water is flowing through the discharge pipe.
Disconnect the check valve and remove any debris.
Check the backup pump’s battery. Periodically test the battery’s charge using a multimeter. If you can, connect a maintenance-free battery to your backup; an AGM (absorbed glass mat) battery is one of the best options for a sump pump.

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.

Sump pump life expectancy

Most pumps last around 7–10 years. The lifespan is shortened by the acidity and cleanliness of the water entering the pump, not to mention how well you take care of it. Basic preventative maintenance as described above will help you get the most out of your sump pump.

Replacing a sump pump

When it comes to water-based appliances like sump pumps, it’s important to make sure you know what you’re doing. A sump pump won’t be very useful if it pulls water out of the sump only to dump it somewhere else inside your house.

The basic steps for replacing a sump pump are:

Shut off power to the old pump at the circuit breaker.
Unplug the old pump and disconnect the water lines, loosening the pipe clamp at the lower end of the check valve.
Remove the old pump.
Place the new pump in the sump pit, ideally resting on a pump stand and not the base of the pit. Make sure the pump is sitting level, and that the float (for the switch) is sitting in the centre of the pit.
Connect the new pump to the check valve and discharge line.
Plug in the new pump and test it by dumping water into the sump. If it doesn’t work, disconnect the power before trying to fix it. Make sure to check for any leakage at the new connections.
Once the pump is working, replace the cover your sump pit.

If your new pump isn’t a perfect match to the old one, you may run into issues connecting it to the discharge lines. If you’re not confident in your pipefitting skills (or any other part of the process) don’t hesitate to contact a pro to install your pump. A small cost upfront is worth it to avoid a failing pump.

Resetting a sump pump

If you need to reset your sump pump, it may be as easy as pressing the reset button on the unit. If it doesn’t have one, either flip the power switch off or completely unplug it.

Once it’s powered off and disconnected, you can remove it from the pit to check for blockages inside. These are the most common source of issues for sump pumps. Remove any obstructions before re-connecting it. Once it’s reset and reconnected, pour some water into the sump to see if the pump turns on to remove it.

Troubleshooting sump pump issues

As long as they have a back-up power source, sump pumps are fairly reliable. Nevertheless, here are some things to watch out for:

Debris in the pump

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.

Clogged or frozen discharge lines

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.

Wrong sized pump

If your pump’s flow rating is inadequate, it could struggle to displace all the water entering your home and burn out the motor.

Missing or broken check valve

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.

Improper connection to sewage line

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).

Float switch stuck on

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.

Not turning on

There are several possible reasons that your sump pump isn’t turning on:

The float switch may be stuck in the off position. Try manually raising the float switch by hand to see if your pump turns on.

Your pump may not be getting enough power. Ensure it’s plugged into a functioning power outlet (test the outlet with something else if you need to) and make sure it hasn’t blown a breaker. Sump pumps should have their own dedicated circuit.

The pump motor could be overheated. If a pump has to operate continuously for too long, or it’s pumping more water than it’s designed for, it might overheat. If your sump pump often overheats, it may be too small.

Your sump pump’s motor could have burnt out. If your sump pump won’t operate despite ample power and a functioning switch, you may need to replace the motor.

The pump could be clogged. Check the pump’s discharge pipe (normally located outside at ground level) to ensure that water can flow smoothly. Then, unplug the pump and inspect the intake for blockage. You may need to remove the pump from the sump pit.

What will your home insurance provider want to know?

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.

Related articles

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.

Is sump pump failure covered by insurance?

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.

Commonly asked questions

How do I know if I need a sump pump?

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 should a sump pump run?

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:

A faulty check valve. The check valve lets water out, but not back in. If it’s malfunctioning, there may be water running back into the sump pit and causing the pump to work harder than normal. Check valves are usually installed near the pump, in the sump pit. Not every sump pump has a check valve installed.

A blocked discharge line. If there’s debris in the outlet pipes, the pump will have to work harder to push water through.

A pump that’s too small. If you can’t find any mechanical issues, but your pump is always working, it may simply be too small for your home. Run the calculations from further up the page to see if you need a more powerful pump.

A change in the water table. Water tables can change over time, especially seasonally. If the water table at your home rises past the height of your sump pit, your pump will run much more often. The fix may not be simple (if indeed it requires a fix); you’ll probably need to find a sump pump professional to see what they suggest.

How does a battery backup work for a sump pump?

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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Sump pumps and your home: A guide