How to Test Your Sump Pump Before Storm Season

Why this matters

A sump pump can sit idle for months and then be asked to run every few minutes for a whole night, often during a storm that also knocks the power out. The time to find out it has a stuck float, a clogged inlet or a buried discharge pipe is a dry afternoon in early spring or late summer, not two in the morning with water rising. The test takes about fifteen minutes and two buckets of water, and it tells you whether the pump starts, whether it moves water, and whether that water actually leaves your property.

Before you start: the pump is an electrical appliance standing in water. Never put your hand or a tool into the basin while the pump is plugged in. If the floor around the basin or the outlet is wet, do not stand in the water to unplug anything; turn the circuit off at the panel from dry floor first, and leave it off until an electrician or plumber has looked. See related: How to Shut Off Power at Your Electrical Panel. If you see scorch marks on the outlet or plug, smell burning, or the cord is cracked or damaged, stop here and call an electrician or a plumber.

For what each part of the system does, see How Your Sump Pump Protects Your Basement. This article is only the test.

What you need

• Two clean 5-gallon buckets, or a garden hose that reaches the basin.
• A flashlight.
• A tape measure.
• A helper outside, or a phone so you can walk out and check yourself.
• Ten minutes of dry weather, so the test water is the only water.

Step 1: Check the power before you add water

Look at how the pump is plugged in. Many pumps use a piggyback plug: the float switch has its own plug with an outlet on the back, and the pump's plug goes into that. Both must be pushed fully into the wall outlet. Some pumps have a single cord with the switch built in.

Check the outlet. Basement outlets are commonly GFCI-protected (a GFCI is the outlet with TEST and RESET buttons, or one protected by such an outlet or breaker elsewhere). If the GFCI has tripped, the pump has no power and will look dead. Press RESET once. If it will not reset, or trips again during the test, that is a stop point: see Step 6 and How to Reset a Tripped GFCI Outlet.

Why first: a pump that fails the water test because it was unplugged teaches you nothing about the pump, and you would have to repeat the test.

Step 2: Look at the outlet outside

Walk outside and find where the discharge pipe ends. It should be open and clear, not buried under mulch, snow, leaves or a flower bed someone built over it, and it should let the water out away from the foundation. A pipe that ends next to the wall sends much of the water back down to the same drain tile it just came out of. Many towns also restrict where a sump may discharge; check before you move it.

Why before the test: a blocked outlet is the most common reason a pump runs and runs but the basin does not drop. Finding it before you pour saves you from watching the pump labor against a closed pipe.

Step 3: Measure where the water is now

Lift the lid and shine the flashlight in. Measure from the rim down to the water surface. In a dry season the water is usually sitting near the pump's off level, because the pump last ran until it shut off. This matters for the next step: one bucket may not be enough to start it.

Step 4: Pour slowly and watch the float

Pour the first bucket in slowly, over 20 or 30 seconds, aimed at the side of the basin rather than straight onto the float. Watch the float switch rise with the water. Pouring slowly lets you see the float move and catches a float that is hung up on the basin wall or the cord.

Keep pouring with the second bucket, or run the hose gently, until the pump starts. Then step back from the basin.

Step 5: Watch it run and listen for it to stop

A healthy test looks like this:

• The pump starts with a hum when the float reaches its on level.
• The water level drops steadily.
• The pump shuts off when the float drops to its off level, usually with a clunk. That clunk is the check valve on the discharge pipe closing so water in the pipe does not fall back.
• Your helper outside sees water come out of the discharge within a few seconds of the pump starting, and it stops shortly after the pump stops.

Put the lid back on when you are done. It keeps debris, children and pets out of the basin.

Step 6: Know when to stop and call

Stop the test and call a plumber, or the company that installed the pump, if you see any of these:

• It hums but the water does not go down. The impeller (the spinning part that moves the water) may be jammed, the inlet screen clogged, or the discharge blocked or frozen. Unplug the pump from dry floor so it does not burn itself out; a pump that is not moving water buys you nothing by running. If the water is near the rim, call now and say so.
• It runs and will not shut off, even after the water is down at the bottom. The float may be stuck up, or the pump may be running dry, which damages it.
• It shuts off and restarts within a few seconds, over and over. The check valve may have failed and the pipe's water is falling straight back in.
• It trips the GFCI or the breaker. Reset once. If it trips again, leave it off and call. Do not plug the pump into an extension cord or a non-GFCI outlet to get around the trip; the trip is telling you there is current leaking where it should not be, next to water.
• It does nothing at all, with good power and water above where it ran last time.
• Grinding, rattling, or a burning smell.

If a storm is forecast and your pump just failed, tell the person you call. A plumber may prioritize it, and you can ask whether to rent or buy a temporary pump in the meantime. Do not try to rewire or bypass the float yourself.

A worked example: the first bucket did nothing

A homeowner tested their pump in late March.

What they measured. The basin is round, 24 inches across inside. The water was sitting 20 inches below the rim. From a previous storm they had marked the on and off levels with a wax pencil: the pump starts when water reaches 15 inches below the rim and stops at 20 inches below. So the water was right at the off level, and the pump needed 5 inches of rise to start.

How much water that takes.

radius            24 in / 2 = 12 in
area              3.14 x 12 x 12 = 452 sq in
water for 5 in    452 x 5 = 2,260 cu in
in gallons        2,260 / 231 = about 9.8 gal
one bucket        5 gal x 231 = 1,155 cu in
rise per bucket   1,155 / 452 = about 2.6 in
two buckets       2.6 x 2 = about 5.1 in

(231 cubic inches make one gallon.) A check from the other direction: 9.8 gallons is just under two 5-gallon buckets, which agrees with two buckets giving about 5.1 inches.

What happened. The first bucket raised the water about 2.6 inches and the pump stayed silent. The homeowner's first thought was that the pump had died. It had not; the water was still about 2.4 inches short of the on level. Near the end of the second bucket the pump started, ran for roughly 20 seconds, and stopped with a clunk at the 20-inch mark. Their partner, outside, saw a steady stream at the end of the extension and saw it stop.

What they found anyway. The stream came out at the end of a plastic extension that had been knocked sideways over the winter and was pointing at the house, about 2 feet from the foundation. They turned it back so it ran out across the lawn. The pump was fine; the water had been going right back to it.

What they wrote down in their records file: date, "two buckets to start, ran about 20 sec, check valve clunk, outlet redirected." Next year they will know what normal looks like. See related: Your House Records File and What Goes In It.

What would change the test

• The pump is a pedestal type, with the motor on a post above the basin and a float on a rod. The test is the same, but you can see the float rod move, and a sticking rod is a common fault.
• You have a battery backup pump. It usually sits slightly higher in the basin and starts only if the main pump fails to keep up. Test it the way its manual says to; many have a test button. Do not test it by unplugging the main pump and leaving it unplugged; plug the main pump back in before you walk away, and check that it is plugged in again the next time you pass the basin.
• You have a high-water alarm. Lift its sensor or pour enough water to reach it, per its instructions, and confirm it sounds. An alarm is what tells you the pump stopped when you are asleep or away.
• The water is already high when you lift the lid, because the ground is wet and the pump is cycling on its own. You do not need to pour anything. Watch one natural cycle from start to stop, with your helper outside, and time how long the basin takes to refill. If it refills in a minute or two in dry weather, write that down and mention it to a plumber: a pump working that hard between storms has less margin when the storm arrives, and it wears out sooner.
• The basin is dry and the bottom is dirt or gravel. If you can see sediment, sand or gravel piling up around the pump inlet, or the water you pour drains away into the ground, call a plumber; a basin that is filling with soil can clog the pump.

How often to test

Once before each wet season is a reasonable baseline, and again after any long dry spell or after work in the basement that might have moved the pump or the cord. A pump that is around ten years old, or that runs often, deserves a more frequent look; ask whether replacing it on your schedule makes more sense than waiting for a storm to decide for you.

References

• See related: How Your Sump Pump Protects Your Basement
• See related: How to Reset a Tripped GFCI Outlet
• See related: How to Shut Off Power at Your Electrical Panel
• See related: When to Stop and Call a Licensed Pro Around the House
• Manufacturer's installation and owner's manual for your pump and any backup or alarm