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How Does a Sump Pump Work in a Basement?

A sump pump installed in a basement of a home with a water powered backup system.

Save your basement from unanticipated or accidental flooding with a working sump pump. Learn how it works and see other alternatives for a flood-free basement.

The modern pump is not a new invention, and it is amazing how much pumps have changed and adapted over the years to meet different needs. Technically, the first pump was probably the shadoof made by ancient Egyptians to raise water, The Archimedean screw pump from 200 BC is still considered one of the greatest inventions of all time, and is still used even in developed countries in places that agricultural fields without the benefit of electricity.

As usual, people adapted the technology they already had to deal with problems that arose, but sump pumps came about because a man who spent his time in the Navy pulling big ships from the water realized that he could use the same technology to help out in his father’s motor shop. Most of the flooding issues he saw were a result of power failure, leading to a need to remove groundwater from commercial and residential basements. And that is how Karl Neidermeyer came to invent the modern sump pump in 1946.

Common drainage and leakage problems in basements

Common drainage and leakage problems in basements.

Wet basements can happen in any home with a basement, old or new. However, they are more likely to happen in older homes which are usually designed to deal with water problems before they start. Whatever kind of home you have, you need to keep an eye on your basement and make sure you don’t have any water problems. The quicker you deal with an issue, the less damage it is likely to do and the less expensive it will be to repair.

Health Effects of Uncheck Moisture

Unchecked moisture can quickly lead to mildew and mold, which will not only ruin the building but could cause serious health problems for your family. Short-term exposure to mold could cause headaches, sore throat, and eye irritation, while long-term exposure could cause more serious problems like asthma even in previously healthy individuals. Long-term exposure could also heighten allergy sensitivities and bronchitis. While water can build up anywhere, it is more common in basements and easier to miss because of the location.

Causes of and Solutions to Basement Leakage

There are several common causes of basement leakage, and you can do something proactive about all of them.

Most homes have been backfilled with loose soil after construction, which commonly settles more than the surrounding, undisturbed soil. If the backfill compresses it can create lower spots that cause water to drain toward the house. Walk around the house and make sure the ground is sloping away. In combination with roof gutters, downspouts, and extensions, regrading the soil around a foundation is one of the best methods of avoiding basement moisture problems.



Patios and walkways could also be causing water to run toward your home. Poor construction or soil settling could change the pitch even if the paved surfaces were originally properly constructed. Depending on their size, it may be possible to change the angle of large concrete slabs. A walkway may be pulled up and redone, or you can seal the paved surface and build a dam to block water. If practical, you can direct the rainwater coming from the house to avoid your patio and walkways.

Your paved driveway could direct the water toward your house, or develop a sunken area near the roof gutter downspouts. If your driveway is flat, it could be holding a lot of water.

Your own and your neighbor’s drainage could also be causing problems for you. You can add extensions to your downspouts to direct water away from your house but your neighbor may be harder to deal with. If you point out that their drainage system is directing water toward your home or that their lawn is poorly graded, they could be annoyed and take it personally. You have legal options where you could compel a neighbor to take corrective action if you can prove they are causing you a harm.

How Do You Know When You Need a Sump Pump?

A burst pipe at the furnace and water tank has caused a leak on the basement floor of a house.

Even if you are doing everything right, you may still need a sump pump to deal with excess water in your basement. Here are the top 5 signs you may need to install a sump pump:

  1. Has your basement flooded before? If so, there is a bigger likelihood that it will happen again.
  2. Do you live in a flat or low-lying area? Even the best construction may not be able to handle a deluge where your area gets a lot of rainfall at once.
  3. Does your area normally get a large amount of rain and/or snow? Flooding may be inevitable when there are regular amounts of water being added to the soil. And it also means your sump pump will have to work hard to deal with all the challenges.
  4. Is your sump pump more than 6 years old? Most sump pumps last about 10 years, so you want to start thinking about whether you need a new one.
  5. Do you have anything in your basement that you need to protect, such as carpeting or furniture? It is better to avoid water problems if you are risking something you don’t want to lose if you have a water event.

How Does a Sump Pump Work in a Basement?

Red plastic drainage pump pumping water with automatic built-in shut-off float.

Sump pumps are small pumps that are installed in the lowest part of a basement or crawlspace to not just keep the building from flooding but to keep it as dry as possible. Water goes into the sump pump through drains or it just naturally travels through the soil. The sump pump is usually in a specially constructed sump pit, and it pumps the water out of the pit and away from the building.

Parts of a Sump Pump

The sump pump stands in a sump pit, which is just a hole made for the pump. The pit is usually only about two feet deep and about a foot-and-a-half wide, with a gravel base, and will be located at the lowest point in your basement or crawl space.

In order to turn on, sump pumps have either a float activator arm or a pressure sensor which triggers them to take care of an incoming problem. The pressure sensor is activated when water is pushing harder on the sensor than air. The float activator arm works like the float in your commode. A ball is on top of the water, and as it rises it raises the arm with it. If either one of those methods fails for some reason, there is also a backup that allows you to turn the pump on manually.

Kinds of Sump Pumps

Water and electricity usually are not a good mix, so one important thing to always keep in mind is that sump pumps do usually use a standard household current, so they will need a grounded outlet. The sump pump is pretty much always near water, so you should have a ground fault circuit interrupt (GFCI) on the outlet itself in order to make sure you prevent electrocution of yourself or someone else. Other than that, though, you won’t need special wiring that could end up being very expensive when you install your sump pump.

  • Centrifugal pumps are the most common for homes. When the motor is on, an impeller turns, using centrifugal force to push water towards the sides of the pipe. When a void is created, water from the pit rushes in to fill the space.
  • Submersible pumps come in two basic designs, the first being submersible. Submersible pumps live up to their name and rest directly in the water. The device is in a waterproof enclosure with the pump at the bottom and the outgoing pipe near the top. The bottom of the pump has a grate which will filter debris, so the machine won’t constantly have other material constantly running through it and possibly building up and clogging or damaging the pump. After the pump is turned on, water simply gets sucked up through the grate and then it travels through pipes on its way out of your home.
  • Pedestal pumps are another common kind of sump pump. Unlike submersible sump pumps, pedestal pumps actually have a pedestal that keeps the pump out of the pit. Even when the pit is full, the pump is away from the water. The pedestal pump looks like a long stick with a fat head on one end and works by having an inlet pipe go down to the bottom of the pit so it can bring water up and out. Being out of the water makes them louder, but pedestal pumps also tend to be less expensive than submersible ones.

Types of Sump Pumps for Basements

Sump pump for suctioning collected ground water in a basement of a house.

Any of the sump pumps already mentioned would work well in a basement. There are considerations you should take into account when choosing the sump pump for your own home.

Again, the pedestal sump pump is noisier and less expensive. There are a lot of reasons you might not want to deal with the loud noise of a pump in your home, especially if you have small children or if loud noises wake you.

You can get a sump pump that doesn’t come on automatically to save some money, but the problem is obviously that it won’t deal with water seepage until you go down and turn it on manually. If the water rises quickly while you are sleeping or away from home, you could end up with a flood pretty quickly.

You can choose a pump with less horsepower, like one-quarter to one-third horsepower, for most homes. You won’t need to purchase something with more power than that. Your home sump pump should probably also operate on 110-volt circuits. Other kinds are available but are normally on practical for industrial uses.

Another important thing to think about is backup and alarm systems. If you don’t expect many problems, there might not be much need, but if your home is prone to flooding you would probably benefit from an alarm that lets you know when there is a problem and at least a backup energy source since power outages often accompany the kinds of weather that would cause flooding.

Alternatives to Sump Pumps for Your Basement

Chimney thermal camera leak investigation.

You may not need a sump pump at all, so before you make the commitment, analyze how much risk you actually have and whether there are other ways to keep your home from taking in extra water. It is better to keep the water out entirely if you can than to let it in and then get rid of it.

How to Protect Against Leakage

First look at the foundation to your house. Is there a space where settling has caused unevenness? You should fill in any gaps anyway to prevent damage to your house.

Examine your gutters and downspouts. Are you deliberately routing rain and snow runoff away from your home? Are there other factors causing excess water on your property? Dealing with the cause of extra water won’t just protect you from water damage but from other kinds of problems.

How to Detect Leakage

Even if you don’t go down to the basement very often, you can get hints that you have a water problem. The first sign might be a musty smell upon entering your home.

If you find water anywhere that it shouldn’t be, you need to find out the source. Checking your basement regularly is important to make sure you are not missing any important clues to problems.

You may find small puddles in the basement. Even a small puddle is a bad sign because it means water is getting in somewhere it shouldn’t. If you find puddles when it has not rained recently, you should investigate immediately.

Check out the foundation and make sure there is no damage. If you suspect leakage but aren’t sure, ask a professional for help.

Additional Options

Once you have examined the obvious, there are other options. After you repair gutters and manage your drainage strategically, there are still other options.

For instance, an outdoor curtain drain can divert excess water to a pond on your property. Before you add what could be a messy project like a sump pump, check out your other options and see if you can get a free consultation with an expert.

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