While hot water tanks and broken plumbing may flood a basement, the typical flooded basement is caused by undiverted rainwater, a basement below the water table, or saturated soils around the foundation. The first lines of defense against flooding are proper grading, properly diverted downspouts, a foundation drain and foundation waterproofing. The last defensive stand is the sump pump.
Pumping the Sump
A sump is a basin or pit located below the basement floor that includes a container and a pump to remove standing water. Some homes also have a perforated drain system around the foundation that directs water to the sump. Others may only have a sump that collects the groundwater around it as it flows into that area naturally. Some homes have no sump at all.
The perforated sump container is surrounded by coarse gravel that filters out debris as water enters the container. The sump pit cover prevents anything from falling in and moisture from flowing out. The system’s pump sends accumulated water through a pipe to the outside and away from the house.
Whatever sump pump is used, it should have a check valve on the sending or discharge pipe to prevent water from flowing back into the basin once the pump turns off.
Sump Pump Types
There are several types of sump pumps with prices that vary depending on horsepower, lift, and operational extras like alarms and battery backup. Pumps may be hard-wired into the home’s electrical system, work off a standard three-prong grounded outlet with a ground fault interrupter, or be connected to the home’s municipal water supply, using pressure from the main to draw water out of the sump. Backup pumps may be powered by battery or generator.
A pedestal sump pump is an upright electric pump with its motor—not meant to get wet—at the top. It works by means of a float-activated switch. When the water rises to the point of the float, the switch turns on the pump. Prices range from $60 to $200.
An electric submersible sump pump is meant to work underwater. Its motor is sealed and oil cooled. It may work off of a float-activated switch or a sealed interior switch. Prices range from $100 to $600.
A water-powered pump is not electric but works by using a valve hooked into the municipal water supply. As the pressurized municipal water flows through the main, suction is created and pulls the water out of the sump and into the discharge pipe. These pumps have a float-activated switch and are typically used as backup during a power outage. Models run about $400.
A battery-powered sump pump is also typically used as a backup. It fits next to the main sump pump and turns on during a power outage, main pump failure, or when the main pump can’t keep up with the inflow of water. Models run from $150 to more than $1,000.
There are also backup sump pumps that are powered by generators. The generators must be rated for the sump pump’s operational needs or wattage required to operate. These numbers are listed on the sump pump. When deciding on a sump pump, it is important to calculate the wattage required for startup of the pump and how many other appliances will require startup power from the generator at the same time.
For older homes that do not have a sump pit, there is a floor-sucker pump that removes water down to an eighth of an inch.
Sizing a Sump Pump
Whatever the pump, it needs to be the correct unit for the job. For example, if a sump fills so fast that the pump is running a lot, the pump may be too small to do the work. Conversely, if flow into the sump is slow, there’s no advantage to a larger pump.
There are two key considerations when choosing a sump pump: Capacity or waterflow; and lift required to discharge the water. Capacity can be determined by considering the area of drainage and depth to the groundwater or by measuring the amount and flow rate of water entering the basin during a heavy rain. Sandy soils have more gallons per minute entering the basin, meaning a larger system capacity, than do clay soils that hold water.
A pump is also judged by the amount of vertical lift required to take the water up through the discharge pipe until that pipe becomes horizontal outside. Sump pumps are rated by how high they can raise the water for discharge without losing flow. Charts or graphs explain the flow versus height-of-lift for each sump pump. Flow is usually shown as gallons per minute or gallons per hour. The height-of-lift is given in feet of vertical lift.
Maintaining the Sump System
Problems do occur, so a sump pump needs occasional check-ups. The float can get hung up and need repositioning. The float may also fail to shut off the pump when the water level drops and need replacing. Debris can clog the pump’s intake screen or valve and need to be cleared. The discharge pipe may be plugged or frozen. Batteries need to be replaced periodically. A pump that sits unused for a long time may seize up.
To check how a pump is working, remove the cover and slowly pour water into the sump until the float rises and starts the pump. When the pump is running, the water level should drop. Once it gets below the float, the float will trigger the pump to turn off. If that is not happening, it’s time for a maintenance call.
Credit: Renovate with Tommy Mac