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Test a sump pump by pouring water into the pit until the float switch rises and the pump starts, then watching it pump the pit down and shut off. Do it every spring, before any forecast of heavy rain, and after a power outage. Then walk outside and confirm the discharge line carries the water well away from the house and is not frozen, crushed, or dumping at the foundation.
A sump pump sits in a pit (the sump) at the low point of a basement or crawlspace, where the footing drains and groundwater collect. When water in the pit rises, a float lifts and switches the pump on; the pump pushes the water up a discharge pipe, through a check valve, and outside. It is the last line between groundwater and the floor, and it is a mechanical device that spends most of its life idle.
What do you need?
A five-gallon bucket of water, a flashlight, gloves, and a helper who can stand outside where the discharge line exits. The bucket is the whole test: it raises the float the way groundwater would. If you have a battery backup, you will also want to know where its charger's indicator light is and how old its battery is.
- A five-gallon bucket of water
- A flashlight
- Gloves (the pit is not clean)
- A helper to watch outside where the discharge exits
What are the steps?
Look in the pit and free the float, pour water until the pump starts, watch it pump down and shut off on its own, listen to the check valve, confirm outside that water came out and went away from the house, then test the battery backup and the water alarm if you have them. The whole test takes about twenty minutes and needs no tools.
- Look in the pit. Remove the lid if there is one. Check that the pump is upright, the float moves freely and is not wedged against the pit wall or the pipe, the power cord is plugged in (some pumps have a piggyback float plug; both plugs should be in), and the pit is free of debris that could jam the float or clog the intake. Done when: the float moves freely by hand.
- Pour water into the pit slowly until the float lifts and the pump starts. Note roughly how much water it took; that tells you the float setting.
- Watch the pump run. It should pump the pit down quickly and shut off on its own when the float drops. Listen for grinding, rattling, or a pump that runs but does not move water. Done when: the pump stops by itself with the pit low.
- Watch the check valve on the discharge pipe. After the pump stops, the water in the pipe should stay put. If you hear it rush back into the pit and the pump starts again, the check valve has failed.
- Go outside (or have the helper there) and confirm water came out of the discharge line, well away from the foundation, onto ground that slopes away or into a drain. Where the water goes matters as much as the pump.
- If you have a battery backup, test it too: unplug the primary pump, pour water until the backup starts, confirm it pumps, then plug the primary back in. Check the battery's age and the charger's indicator; batteries in backups need replacing on the manufacturer's schedule.
- If you have a water alarm in the pit (a small float alarm that sounds when water rises above the pump's level), test it by lifting its float. If you do not have one, they are inexpensive and they are how you find out the pump failed before the floor does.
What should you do before winter?
A discharge line that freezes is the same as a failed pump. Where the line runs outside above ground, slope it so it drains empty after each cycle, or fit a freeze-relief fitting near the house that lets water escape if the line ices up. Do not let the discharge end sit in snow or in a puddle that will freeze. The freeze-protection guide covers the rest of the exposed plumbing.
When should you stop and call a pro?
Call a plumber if the pump does not start when the float lifts (after you have confirmed power and a free float), if it runs constantly, if it runs but does not lower the pit, if it is more than a decade old and has never been replaced, or if the pit fills faster than the pump can empty it during a normal rain (a capacity or drainage problem).
Do not reach into a pit with the pump powered. If the basement has water on the floor near any outlet or the panel, turn off power at the main before going down.
In a new home, ask the builder where the discharge line terminates and whether the footing drains connect to the sump; that drawing is hard to get later, and a discharge line that ends in the yard next to the foundation is a builder item.
What should you record?
Each test date, how the pump behaved, the check valve result, the battery's install date, and where the discharge goes. The pump's model and install date tell you when to plan a replacement before it fails. Set the spring test and the pre-storm test as recurring tasks; the Storm Prep pack in the Seasonal Checklist includes the pump.
Common questions
How often should I test the sump pump?
Each spring before the wet season, before any forecast of heavy rain, and after any power outage. A pump that sits idle for months can seize or its float can stick; the test takes a bucket of water and five minutes.
Do I need a battery backup?
If a wet basement would cost you real money, yes. The storms that flood basements are the storms that knock out power, and a primary pump without power is a hole in the floor. A battery-backup pump or a water-powered backup runs when the primary cannot. FEMA lists a battery-backup sump pump among the steps to protect a home from flooding.
The pump runs but the water comes right back. What is wrong?
Usually the check valve on the discharge pipe, which is supposed to stop the pumped water from draining back into the pit when the pump stops. If it fails, the pump cycles constantly and wears out. The valve is a replaceable part on the vertical pipe above the pump. It can also be a discharge line that is frozen or blocked, so check outside.
What should you do next?
If the test was fine and you have no backup, price one this week; it is cheaper than one wet carpet. Then read the storm and freeze prep post for the rest of the list that goes with the pump.
