This is an updated version of the product training course introduced by SUPPLY HOUSE TIMES in 1979, authored by Don Arnold.

Though a sump pump can be used for other purposes, the two most common uses involve the removal of ground water from around the perimeter of a building foundation or the pumping of laundry discharge to a higher-level drain connection. In the case of the former, such an installation prevents seepage and flooding into basements and crawl spaces. Unlike most of the products covered in this course, sump pumps tend to be somewhat regional in their application: standard equipment in certain areas of the country, rarely used in others. Another way to define this is based on the construction of the foundation - whether or not there is a basement (or sub-grade crawl space).


Before we look at the mechanical makeup of these products, let's look at the input and output aspects of an installation used for discharging ground water. First of all, if the sump pump is to dispose of ground water drainage, there must be a network of piping in the ground around and/or under the house to collect it. This usually takes the form of a loop of drain tile around the foundation. Drain tile is loosely jointed or perforated drainage piping material, constructed of clay, composition or plastic, which permits ground drainage to seep in. Such a loop is usually laid just outside the foundation footing in the case of new construction, or just inside the footing in the case of a retrofit installation. The water seeping into the drain tile is collected in a pit, called a sump. In the overall water-draining network, the sump is positioned at the lowest point, using gravity to get the water there. This water is removed by the pump when the level in the pit rises to a predetermined level, causing the float switch to activate. As the level drops, the float switch cuts out again, completing the cycle. Water is evacuated outside the building through a discharge line (most codes do not allow direct connection to the sanitary sewer system for ground water discharge). Laundry sump pump systems, on the other hand, do discharge into the sanitary sewer.

Let's move on now to examine each of the basic components in a typical sump pump installation.


You might be wondering what there is to say about a hole in the ground, but there's actually a bit more to it than that. Ideally located in the lowest portion of the basement, the sump usually has a minimum diameter of 18 inches and a depth of 24 inches. Actually, that part of the system properly called the sump is not the hole in the ground, but rather a liner for that hole, typically constructed of concrete, clay, fiberglass, steel or polyethylene. The sump will have a solid bottom to support the pump inside, unless there is a problem with excessive ground water pressure against the basement floor. In this case, a gravel bottom must be used, and a solid base (such as bricks or a steel plate) should be provided as a base for the pump. Finally, there is a cover for the sump, the purpose of which is to keep possible odors and vermin in, and keep foreign objects (like small children, for instance) out. Such lids are typically specified to withstand a load of about 200 lb.


In terms of basic design, there are two types of sump pumps offered today: submersible and pedestal. As in the case of submersible well pumps, the former is placed in its entirety - motor and all - right down in the water. This makes for a relatively compact assembly, with no mechanical parts protruding through the lid of the sump. The pedestal style of design uses essentially the same type of pumping components as the submersible, but its motor is positioned above the water level, linked to the impeller by means of a shaft inside a column. Manufacturers offer a range of power options for the motor, 1/3 and 1/2 hp being most common. There are minor variations on these basic designs, such as the exact location of the water inlet, but generally speaking, these are the basic configurations and options available in the pumps themselves. In addition, there is a “specialty” category in the field of sump pumps, generally specified for back-up or emergency purposes. In other words, should there be a power failure of the sump pump itself, this alternative pump takes over and handles the function of draining the sump on a short-term basis (until the main unit is back in operation). Such designs are usually powered by an automobile-type battery. In this case, the motor control (float or other provision) for the emergency unit is placed just above the point of activation for the regular sump pump. This way, as long as the primary pump is operating properly, the emergency unit will not kick in. Should the primary unit fail for any reason, the water level in the sump will rise slightly higher, activating the back-up unit. Also available is a water-powered backup type that uses the home's pressurized supply water to evacuate the sump (usually through a venturi action).


Sump pumps are equipped with automatic controls to turn the pump on and off in response to the water level in the pit. Float type switches are still the norm, with diaphragm types usually considered an upgrade option. Within the float category are: (1) vertical action types in which a ball moves a linkage rod to the switch up and down, and (2) tethered types that incorporate the switch internally within the float (pivoting up and down in the pit from the point they are fastened to pump or discharge pipe). Pressure (diaphragm) controls respond to the head of water in the sump (weight of the water). When the sump reaches its “high limit,” the pressure of the water pushes in the diaphragm, and the connecting linkage switches on the pump. As the water level descends, and the weight of the water lessens, the diaphragm switch (spring-loaded toward the “off' position) turns off.


The piping used to discharge water from the sump should be sized according to the outlet port of the pump, usually 1-1/4 inches in diameter on domestic size units. The most common piping materials used today are the plastic types, typically PVC and/or ABS. To prevent discharge water still in the vertical line from running back down into the sump after the pump cuts out, most installations include a check valve positioned just above the pump.