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What does the Federal Emergency Management Agency (FEMA) have to do with sump pumps? It’s the government agency that deals with disaster and anyone who’s ever suffered a flooded basement knows that’s just the right word for it. A recent report by FEMA highlights an interesting trend.Calls to emergency agencies such as fire departments to pump out flooded basements have drastically declined over the past 25 years. The reason is clear. Many localities now strongly advise or require homeowners to install a sump pump in existing houses if the property is prone to inundation from below-grade water. And, in 1987, the Federal Clean Water Act began requiring sump pumps in new construction—even in houses where the flooding potential is minimal.  An electric sump pump is installed in an opening in the basement floor and automatically actuates to remove rising ground water before it can reach flood proportions. The water is conveyed out of the basement into the yard through a permanent pipe. The widespread installation of residential sump pumps is a success story every homeowner can take advantage of. 

More than half of all homes in the United States have moisture infiltrating into the basement or crawl space from the soil beneath the house. The problem may be limited to simply perpetual dampness that spawns the growth of unhealthy mold or mildew. Or, under the right conditions, it can evolve into a catastrophic flood scenario that inflicts thousands of dollars in property damage. The deciding factor is the water table—a source of underground water naturally occurring at some depth. The water table may be a hundred feet below the surface or as little as six inches. Many low-lying areas in Florida have ground water very close to the surface. When the foundation of a home intrudes into the water table in the soil below, the upward movement of migrating water exerts a continuous force known as hydrostatic pressure on the underside of a concrete basement floor.

The threat of water damage from a high water table may be continuous or deceptively transient, depending on the soil type and underground geology. The exact depth of the water table is often a moving target, rising and falling in response to conditions such as rainfall. A water table that normally lurks safely deep underground may surge to the surface and inundate a basement after an unusually heavy deluge of rain. For that reason, being prepared with a sump pump permanently installed in your basement or crawl space is the best insurance against major property damage.

The Sump Basin

Sump pumps require access to the soil below your basement floor or crawl space in order to remove water as it accumulates. In the basement, this means excavating through the concrete floor into the ground beneath. Called a sump basin or pit, the opening is normally located at the lowest spot in the basement or at an area where water infiltration is visually obvious, such as where moisture is observed “weeping” through the floor. A sump pump requires regular maintenance so placement of the sump basin should take into consideration accessibility issues, too. Most sump basins are circular and about 2 feet in diameter with a water capacity ranging from 15 to 25 gallons. The excavation should be deep enough so the basin will penetrate up to 30 inches into the soil below the floor. The bottom of the basin is normally covered with a layer of coarse gravel.  

What Kind of Sump Pump?

All sump pumps accomplish the same purpose but the designs fall into two distinct categories:


A submersible sump pump is installed entirely within the sump basin. When water is present, some or all of the pump will be submerged. As the water level rises, a float switch or pressure switch energizes the pump motor and the pump operates just long enough to pump the basin down to the minimum water level. Submersible pumps offer some advantages over dry installations. Because the pump motor is underwater while it is energized, it runs cooler and may last longer. Also, since the pump, motor and switch mechanism are all located within the basin, a lid can be placed over the top of the basin to completely enclose it, providing a less intrusive installation. 


Mounted on a stand above the sump basin instead of in it, most of a pedestal sump pump remains dry. Only a suction pipe and a float or pressure switch protrude down into the basin. Accessibility is the main benefit of this arrangement. Because the electric motor, the pump chamber and the electrical connections are not submerged in the basin, routine maintenance is less problematic and switching out components is easier when required. However, the exposed equipment does create some hindrance for residents when walking across the floor.

Sizing Up a Pump for Your Basement

The electric motors that drive sump pumps are rated by horsepower. The most common units for residential applications are 1/3 or 1/2 horsepower. Sizing a pump for your needs depends on these variables:

  • The size in square feet of the basement or area to be drained.
  • The usual rate of water accumulation in the sump basin plus a safety margin for contingencies such as extended periods of rain or a flood from a non-natural source like a ruptured water line in the basement.
  • The diameter of the discharge pipe that conveys sump water out of the basement. 
  • The vertical distance in feet that the water must be lifted to reach ground level. 
  • The horizontal distance of the pipe leading out to the discharge point in the back yard.

The float switch is normally adjusted to energize the pump if the water level exceeds about one-third of the basin’s total capacity. That’s usually around 5 gallons. Most residential pumps require a nearby three-wire grounded electrical outlet rated at 15 amps. Due to the nearby presence of water, a Ground Fault Circuit Interrupter (GFCI) outlet is recommended.  A water leak alarm is also a good idea to alert residents if the pump fails and water overflows the basin.

Where Does the Water Go?

Most local codes strictly prohibit pumping sump water down a household drain or the storm drain in the street. Usually, the pump is plumbed to a PVC drain pipe that extends from the basement up to ground level. These considerations should guide decisions about proper drainage:

  • The discharge point at the end of the pipe should be at least 20 feet from the house.
  • Discharge should occur at a point where water will not be sucked back into the house, causing the pump to continuously cycle on and off.
  • Discharged sump water should not flow across property lines without approval from neighbors.
  • In houses with a septic tank, sump discharge should not drain into the septic system.


In many residences, sump pumps may sit inactive in a dry sump basin most of the time. Only when conditions such as heavy rainfall occur are the pumps activated by the influx of ground water. But sump pumps must be in working order 365 days a year because the critical time when they’re needed may arrive without notice. These pumps are generally very heavy duty and engineered to self-actuate and operate without much attention. However, the following maintenance tasks should be observed annually. Do these at a time when the basin is empty.  If checking the pump requires reaching down into sump water, leave the maintenance to a professional plumber, instead.

  • Unplug the pump and plug a lamp or a circuit tester into the AC outlet to verify power at the outlet.
  • Verify that the pump inlet is not obstructed by debris. Check it regularly and especially after it has expelled a large amount of water following a heavy influx. 
  • Make sure the float is not jammed or pushed against the side of the basin where it cannot freely move to actuate the switch.  
  • Pour enough water into the basin to raise the float and actuate the switch. Verify that the pump turns on and off properly. 

What About Backup?

The extreme weather conditions that may contribute to an inundation of ground water are the same conditions that often result in a power failure that inactivates electric sump pumps. Battery backup pumps utilize 12-volt deep cycle marine batteries that provide long pump run times to keep bailing out the basement if the primary pump fails. For even longer backup time, a backup pump that runs off municipal water pressure (which is seldom interrupted by weather events) can also be installed for power-free protection.

Serving Sarasota and Bradenton homeowners for almost 40 years, Aqua Plumbing & Air is the region’s most trusted name in plumbing and HVAC expertise. Ask us for more information about the extra protection against property damage provided by sump pumps and how you can add it to your home today. 

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