A sump pump is a basic part of a system to keep you basement dry. Technically a sump is depression that receives drainage. In your basement, this is a pit where ground water is collected instead. The alternative of collecting water into a sump, is to let your basement flood.
To get water out of the sump, a sump pump is employed. There are two basic sump pump styles: pedestal and submersible.
The pedestal pump has the motor mounted on top of the pedestal. The base of the pedestal is placed into the sump. The sump pump is located at the base of the pedestal. The motor is not designed to get wet. A ball float is used to turn the pump is on and off. With a pedestal pump, the action of the ball is easily seen making it easy to determine if the on-off switch is working.
Pedestal Sump Pump
A submersible sump pump is entirely mounted inside the sump pit. Because it is in the pit, the motor and pump will go underwater as the water in level rises. The on/off switch is attached to a pump. The switch and all motor and electrical connections are specially sealed to prevent electrical short circuits.
A submersible pump generally uses one of two basic mechanisms to turn the pump on and off. The first basic switching mechanism is a float. The float operates similarly to float mechanism of the pedestal pump, the sump float is connect to the switch.
The second basic mechanism is a pressure switch. The deeper the water, the greater the water pressure. So pressure is used to indicate the water level. When the reaches a certain level, water pressure trips a mercury-activated pressure switch.
Both types of switching mechanisms are reliable, However, the sump pump float can become stuck or entangled if it is used in too small of a diameter sump well.
The sump pump pumps water up and out of the basement to somewhere outside, preferably far from the basement. The water needs to be directed far from the basement so that it will not recycle itself back into your sump as ground water. Often, sump water is directed into the downspout drainage system.
Since pump must pump the water up and out of the basement, not all of the water makes it out when the pump stops. The water that did not make it out of the basement will naturally flow back into the sump. A check valve is used to prevent this.
A check valve only allows water to flow one way in a pipe. In case of a sump pump, the water flow is directed out of the basement and the sump check valve prevents it from flowing back in.