Sump Pump Not Working

A sump pump that won’t turn on almost always has one of four causes: a dead or stuck float switch, a tripped GFCI outlet, a failed run capacitor, or a burned-out motor. In Tampa Bay, where the pump sits dry for eight or nine months and then faces continuous demand from June through September, these failures cluster right at the start of rainy season, when you need the pump most.

Why Tampa Bay Sump Pumps Fail at the Worst Time

Most of Hillsborough County gets fewer than 50 days of measurable rain between October and May. That means a residential sump pump can sit completely idle for months at a stretch. Seals dry out, float switches stick in the down position, and capacitors that hold a charge degrade when they are never called on to start a motor.

Then June arrives. The rainy season shifts on like a switch, dropping two to four inches in a single afternoon storm. The pump that worked fine last September now will not start. The pit fills, water creeps toward the crawl space or utility room floor, and you are calling a plumber in the middle of a storm. We see this pattern every single year across Brandon, Riverview, Wesley Chapel, and the low-lying neighborhoods near the Hillsborough and Alafia rivers.

Understanding why the pump failed means you can fix the right thing the first time and not replace parts that do not need replacing.

Troubleshooting Step 1: Check the GFCI Outlet First

Before assuming the pump itself is broken, walk to the outlet the pump is plugged into. Florida Building Code requires sump pump outlets to be GFCI-protected. These outlets have a test and reset button between the two plug slots, and they trip during power surges, which happen constantly in Tampa Bay lightning storms.

A tripped GFCI looks normal. The outlet does not look burned or damaged, and nothing visible indicates a problem. The only way to check it is to press the reset button and listen for a click. If the GFCI tripped, that single button press restores power.

Before plugging the pump back in, test the outlet with a lamp or a phone charger. If the test device works, the outlet has power. If the GFCI trips again immediately, there is a wiring issue or a problem with the pump motor drawing too much current, and you need a licensed plumber to diagnose it safely.

Troubleshooting Step 2: Manually Lift the Float Switch

The float switch is the single most common point of failure in residential sump pumps. It is a buoyant arm or ball that rises with the water level and triggers the pump motor when it reaches the set height. When the float sticks in the down position, the pump never receives the signal to start, even as water fills the pit.

To test the float, make sure the pump is plugged into a working outlet, then reach into the pit and gently lift the float by hand. The pump should start within one to two seconds. If it does, the float is the problem. If the pump does not start when you manually trigger the float, the issue is in the motor or its electrical components.

Float switches get stuck for a few reasons. The float arm can become tangled with the pump’s power cord inside the pit. Debris, sand, or sediment from the pit floor can jam the pivot point. In pits that sit dry for months, the float mechanism can bind from lack of movement. A thorough inspection of the pit usually reveals the cause.

Troubleshooting Step 3: Listen to the Motor

With power confirmed at the outlet and the float manually triggered, pay close attention to what the motor does:

• Silence (no sound at all): The motor is not receiving power, or the motor windings have completely failed. Check the power cord for damage. If the cord is fine and the outlet is live, the motor needs to be replaced.
• Humming but no water movement: This is a classic capacitor failure. The run capacitor gives the motor the initial burst of energy needed to start spinning. A failed capacitor means the motor draws current and hums but cannot overcome the starting resistance. You may also smell a slight burning odor. A humming pump left running will overheat and burn out the motor within minutes, so unplug it if this is what you hear.
• Grinding or rattling: The impeller (the spinning disc that moves water) is broken, jammed with debris, or the bearings are worn. A grinding pump is moving toward complete failure and needs immediate service.
• Motor runs, water level not dropping: The discharge line is blocked. Water is being moved by the impeller but cannot exit the system. Check the discharge pipe exterior for blockages, and inspect the check valve on the discharge line inside the pit area.

Troubleshooting Step 4: Check the Discharge Line

If the motor runs but the pit water level is not dropping, go outside and find the discharge pipe exit point. In most Hillsborough County homes, this exits through the foundation wall or comes up through the ground near the exterior of the house. Look for:

• Mulch or soil packed around the exit opening, blocking flow
• A small mesh screen or cap that has become clogged with debris
• A kinked flexible section of discharge hose (common in older installations)
• Roots or insect nests inside the pipe end (we see this in late spring before the pump has run recently)

While a true frozen discharge line is essentially unheard of in Tampa Bay, a fully blocked line produces the same result: water pumped in but nowhere to go, causing the motor to run under load continuously until it overheats.

Common Causes at a Glance

Float Switch Failure: The Leading Cause in Tampa Bay

We replace float switches more than any other sump pump component. In a climate where a pump might run daily for four months and then go dormant for eight, the float mechanism takes on-off cycling stress in a compressed period. Tethered float switches (ball on a cord) are particularly prone to tangling with the pump power cord inside the pit, especially in narrow pits common in homes built in the 1990s and 2000s in areas like Lutz, Land O Lakes, and Carrollwood.

A quality replacement float switch with a vertical activation style, mounted on the pump body rather than tethered, is more reliable in tight pits and resists tangling. When we replace a float switch, we also inspect the pit for debris that can cause the switch to bind in the future.

Capacitor Failure: Why the Pump Hums but Won’t Pump

A run capacitor is a small cylindrical component inside the motor housing that stores and releases electrical energy to start the motor spinning under load. When it fails, the motor receives power and buzzes but cannot generate enough torque to start the impeller. This is common in pumps that have sat idle for several months, as capacitors can lose their charge retention over time, particularly in Florida’s heat.

A humming pump is drawing full amperage without turning. Left plugged in, it will overheat and burn out the motor windings within minutes. If you hear a hum from the pit, unplug the pump immediately and call us. Replacing the capacitor alone runs $279, which is far less than replacing the entire pump motor. The catch is that a capacitor failure in a pump more than six or seven years old is often a sign the motor is nearing the end of its service life, and we will give you an honest assessment of whether a repair or a full replacement makes more financial sense.

Repair vs. Replace: How to Think About It

The general rule we use with homeowners across Hillsborough County is this: if the pump is under five years old, repair the specific failed component. If the pump is seven years or older and the repair cost exceeds 50 percent of a new pump installed, replace it.

A new 1/2 horsepower submersible pump, properly installed with a fresh float switch, check valve, and discharge connection, costs $950 to $1,250 installed and comes with a manufacturer warranty. That is real peace of mind going into a Tampa Bay hurricane season. In flood-prone areas like Apollo Beach, Gibsonton, Ruskin, and neighborhoods near Tampa Bay or Old Tampa Bay, we also recommend adding a battery backup system at the time of replacement so the pump keeps working through the power outages that almost always accompany the worst storms.

Repair Costs in Tampa Bay

Every service call includes a free diagnosis. The $279 minimum applies to approved repair labor, not to the visit or the inspection.

Pre-Season Testing: Do This Every May

The single best thing you can do to prevent a sump pump failure during Tampa Bay rainy season is to test the pump in May before the first heavy rains arrive. This takes about 15 minutes:

1. Fill the pit slowly with a garden hose. Watch the float rise and confirm the pump starts automatically before the water reaches six inches from the top of the pit.
2. Confirm water is exiting the discharge pipe outside. Go look at the exterior exit point while the pump is running.
3. Listen to the motor. It should run smoothly without grinding, rattling, or straining sounds.
4. Test the battery backup if you have one. Most backup controllers have a test button. Confirm the backup pump starts and that the battery holds a charge.
5. Inspect the float switch for tangling or binding in the pit. A quick visual check takes 30 seconds.

If the pump is slow to start, takes more than a few seconds to begin clearing water, or makes any unusual sound, schedule a service call before June. We are typically backlogged on sump pump calls from late June through August when the storms are active.

What to Do If the Pit Is Filling Right Now

If you are reading this during active rain with water rising in the pit and the pump is not working, here is what to do while waiting for a plumber:

• Reset the GFCI outlet immediately. This fixes the problem in a meaningful percentage of emergency calls.
• If the motor hums, unplug it. A humming pump is not pumping and is burning itself out.
• Move valuables, electrical equipment, and anything stored on the floor away from the area.
• If you have a wet/dry shop vacuum with a large capacity, you can manually remove water from the pit to buy time. It is slow but can prevent overflow while help is on the way.
• Do not wade into standing water near any electrical panel or outlet.

Frequently Asked Questions

A sump pump that will not start during a Tampa Bay rainstorm is an emergency, not a project for next week. Our licensed plumbers (CFC1431159) serve Hillsborough, Pasco, and Pinellas counties with same-day availability, free diagnosis on every call, and straight prices before any work begins. Call (813) 343-2212 or visit callhometherapist.com/plumbing to get a plumber who understands what Florida’s rainy season and hurricane season demand from your sump system.