How Does a Sump Pump Work?

Last Updated on by Anthony Brown

Installed in sump pits located in lower areas of crawlspaces or basements, sump pumps prevent flooding by pumping water out of the sump pit and away from buildings.

Although sump pumps used to be seen only in buildings constructed in low-lying regions prone to flooding, amendments included in the U.S. Federal Clean Water Act in 1987 and other legislation made the installation of sump pumps a requirement even in buildings not at risk for flooding.

In fact, sump pumps are a common fixture in most new homes today, with the exception of residential and commercial structures located in the southwest – but how to they work?

How Sump Pumps Work

Most sump pumps are activated by a float switch at the bottom of the pump pit. When the water level rises the float switch begins to float and activates the sump pump.

How it Works

  1. Water pools at the bottom of your sump pit
  2. The float switch floats as the water levels rises
  3. The sump pump turns on and starts pumping water

How Does a Sump Pump Prevent Water from Rising in a Basement?

As sump pits fill with overflow, sump pumps should automatically start working via a float switch or pressure sensor, pumping water out of the pit, into pipes and out of the building. 

Pressure sensors behave like float activators by sensing pressure exerted by excess water, which causes the sump pump to activate. 

Assisting float switches in preventing basement flooding are check valves that stop water from flowing back into the sump pit.

What Happens After My Sump Pump’s Motor Turns On?

When your pump senses water pressure, the motor activates and a fan-like component called the impeller starts turning.

The spinning action of the impeller produces centrifugal force, which pushes water against the sides of piping.

Centrifugal force also creates an area of low pressure in the sump pit that attracts water. The spinning activity of the impeller then thrusts water through the piping and out your home.

How Does a Submersible Sump Pump Work?

Encased in waterproof material, submersible sump pumps actually rest in the sump pit, with the pump at the bottom of the pit and an outlet pipe on top.

A grate or screen covers the bottom of the sump pump to prevent debris from clogging pipes.

When activated, a submersible sump pump sucks water up through the screen, routes water into piping and out of your residence.

Advantages of submersible sump pumps include resistance to overheating failures and quieter operation.

How Does a Pedestal Sump Pump Work?

Installed outside of sump pits, pedestal sump pumps operate by extending an inlet pipe into the pit’s bottom to suck out excess water.

Consisting of the same, basic components as submersible sump pumps, pedestal pumps are noisier, since they sit outside the pit, but have the advantage of being less expensive than submersible pumps.

You might consider a pedestal pump if you frequently experience flooded crawl spaces or basements, have space issues or plan to install a sump pump yourself.

What does a Sump Pump Look Like?

Components used to make sump pumps in the U.S. are standardized and consist of a concrete, metal or plastic compound sump basin (usually about two feet by two to three feet deep) and a metal or plastic canister lining the sump pump basin.

Sump basins may hold up to 25 gallons of water or more, depending on the size of your basement and where you live. You should see PVC piping extending from a sump pump to a check valve.

Sump pump check valves resemble the size and shape of spark plugs and may be installed horizontally or vertically.

Will a Sump Pump Operate in Non-Concrete Crawlspaces?

A sump pump’s ability to remove water from your basement or crawlspace depends largely on pipes remaining clean and debris-free.

Pipes clogged with dirt or pebbles force the sump pump to work harder, potentially leading to overheating and failure.

If you have crawlspaces made of pea gravel, for example, you should consider investing in an ejector sump pump. These cast-iron pumps have two inch ejector ports and enhanced impellers to allowing processing of small gravel pieces without harming the pump.

How Do I Know My Sump Pump is Working Properly?

Battery-powered sump pump flood alarms will notify you in case your pump is failing and water is not being pumped out of your basement.

More sophisticated sump pump alarms will send notifications to your smart phone if basement flooding is imminent due to a faulty sump pump.

However, by performing periodic maintenance on your sump pump, the chance of sump pump failure is minimal to none.

Why Would a Sump Pump Stop Working?

Common reasons why sump pumps fail to remove excess water include clogged or frozen discharge pipes, switch problems occurring if your pump shifts position and renders the float switch ineffective and homeowners using the wrong size sump pump.

As a rule, smaller sump pumps function just as well as larger ones. If your sump pump is too big for what it needs to do, the motor tends to work harder, reducing the life-span of the pump. However, if you suffer regular basement flooding, a too-small sump pump won’t be able to keep your basement dry.

You can learn more about sump pump operation and how to choose the correct sump pump for your home or business by visiting the U.S. government’s page on sump pump information.

Sump Pump Life Expectancy

Most sump pumps work for about 10 years before they need to be replaced. Cheaper models made of plastic tend to break down in 5 years while metal pumps last much longer. The more your pump works the shorter its life will be so plan accordingly!