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Sump pumps: how to test one and keep the basement dry

A sump pump is the last line of defense for a basement. Most fail quietly, so the time to check yours is before the next big storm.

The short answer

Pour a bucket of water into the pit: the pump should start on its own and empty it quickly. FEMA advises checking at least once a year and cleaning the inlet screen. Consider a battery backup – storms that cause flooding also cause power outages. Discharge the water away from the house, and never into the sanitary sewer.

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What a sump pump does

A sump pump collects groundwater near the foundation in a pit and pumps it out to the yard, keeping the basement dry, as the City of Edina, Minnesota describes it. FEMA calls sump pumps an excellent defense against basement seepage and flooding.

How to test it

  1. Pour a bucket of water slowly into the pit (FEMA).
  2. The pump should switch on automatically and pump the water out quickly (Edina).
  3. Check that water is coming out of the discharge pipe outside.
  4. Listen for grinding or rattling, and check the float moves freely.

FEMA advises checking the pump at least once a year and cleaning its inlet screen with a wire brush, ideally more often.

When the power goes out

Heavy storms are when you need the pump most, and when power is most likely to fail. Battery-backup sump pumps are available, or a generator can run the pump during an outage, Edina notes. A water alarm in the pit is a cheap early warning.

Where the water can go

  • Edina advises directing discharge away from the house toward lawn or other areas where it can soak in, or toward public drainage paths.
  • Not into the sanitary sewer. Many cities prohibit it – in Lincoln, Nebraska it violates municipal code. Lincoln explains that one sump pump running 10 minutes an hour into the sewer equals the normal sewage of 12 homes, which can cause sewer backups for everyone.
  • Some cities require a permit to drain sump water to the storm sewer, as Edina does. Check with your city.

When to call a plumber

  • The pump does not start in the bucket test, or runs constantly.
  • It is more than several years old and you have never tested it.
  • The discharge line is frozen, buried or drains back toward the house.
  • You want a battery backup or a second pump added.
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Questions

How do I test my sump pump?

Pour a bucket of water into the pit. The pump should start automatically and pump the water out quickly. FEMA advises checking it at least once a year.

Do I need a battery backup sump pump?

If your basement floods during storms, it is worth considering. Storms often cut power, and a battery-backup pump or a generator keeps the pump running.

Can a sump pump drain into the sewer?

Usually not. Many cities prohibit connecting a sump pump to the sanitary sewer because it overloads the system. Ask your city where discharge may go.

How often should a sump pump be checked?

FEMA advises at least once a year, plus cleaning the inlet screen, ideally more than once a year.

Related guides

Sewer backup: what to do, and how to stop it happening againSewage coming up through a floor drain, tub or toilet is a health hazard and usually a blockage in the line from your house to the street. Here is what to do first.Frozen pipes: how to prevent them and thaw them safelyA frozen pipe can split and flood a home when it thaws. Here is how to keep pipes from freezing, how to thaw one safely, and what to do if one bursts.How to find a hidden water leakA higher water bill or the sound of water running when nothing is on are the usual first clues. Your water meter can tell you in two hours whether you have a leak.

Sources

Facts and figures in this guide come from these official and manufacturer sources, checked October 2026:

  1. FEMA – Maintain your sump pump
  2. FEMA – Protect your home from future flooding
  3. City of Edina, MN – Sump pumps (PDF)
  4. Lincoln Transportation and Utilities, NE – Sump pump connections

Updated October 2026 by the Plumbers Pages editorial team. General information for homeowners, not professional advice – codes and equipment differ, so follow your product’s manual and local rules. When gas, electricity, sewage or anyone’s safety is involved, call 911, your utility or a licensed plumber. How we write our guides · Plumbing glossary

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