Sump Pumps

Sump pumps are generally used in residential applications to remove rain or groundwater that has gathered in a collecting (sump) pit, to clear regularly flooded basements, or where the water table is located above the home’s foundation. Sump pumps are also effective in commercial or industrial applications, where the ground or soil can become unstable due to over saturation water. These pumps are designed to only handle ground

water, and are not intended to pump solids larger than fine soil. Sump pumps are also meant for intermittent, not continuous operation.

Sump pumps can be either manually or automatically operated. An automatic sump will usually feature a low water level switch, which will activate the pump when the water reaches a pre-set level. Battery-powered back-up sump systems may be purchased separately, so that in the event the primary sump pump is compromised (due to a power outage or another obstruction), the water will still be removed as necessary.

Little Giant Sump Pumps

A division of Franklin Electric, Little Giant has been a world-wide producer of water and fueling systems for over 60 years. Every Little Giant pump is tested for capacity and control, prior to being distributed; these pumps are known for their reliability as well as their versatility, and can be used for a number of residential and commercial applications. These sump pumps are capable of handling large volumes of water, which makes them suitable to many dewatering and water transfer applications. Little Giant pumps are available in manual and automatic configurations; the automatic pumps utilize either an internal (diaphragm) switch, or an external (float) switch to activate the sump pump when the water reaches a pre-set level.

Little Giant offers several series of submersible sump pumps, ranging from 4/10 HP to 1/2 HP motors. Little Giant cast iron and bronze pumps feature epoxy coated housing so as to prevent corrosion for these submersible pumps. Some Little Giant sump pumps are available with additional features, such as a high-water alarm, a longer cord, or a battery back-up option.  

Liberty Sump Pumps

A New York-based company, Liberty Pumps, is a nationally recognized manufacturer of quality pumps. Liberty offers a wide range of sump pumps, which are suitable for a variety of light to heavy-duty applications, including high temperature demands. These pumps come in a choice of materials: plastic, cast iron, or aluminum. Typically, plastic sump pumps are utilized for light-duty applications, or for projects with a limited budget. Aluminum pumps are lightweight and energy efficient, often used for medium-duty pumping requirements. Cast iron is the most common type of material used, and these pumps are commonly found in heavy sump applications.

Liberty sump pumps are available with either manual or automatic operation; the automatic pumps feature one of three types of float switch that activates the pump when the water reaches a pre-set level. The type of switch on a pump should be noted, as some switches, such as the wide angle float, require more space for installation. The mechanical float switch, on the other hand, require the least amount of space. Piggyback switches are removable, which allows manual operation of the sump pump if necessary.

Types

Manual Sump Pumps

Manual sump pumps must be switched on and off prior to and at the end of each individual run. Automatic pumps with a piggyback float switch can be operated manually if the switch is removed.

Automatic Sump Pumps

Diaphragm pressure switches are only found in Little Giant sump pumps. These internal switches typically feature a rubber sensing diaphragm, which notes changes in static pressure. As the water level increases, the pressure against the diaphragm increases; when the pressure gets high enough, the diaphragm presses against the attached spring, which activates the switch.

Diaphragm switches are preferable to float switches in applications which experience shaking and splashing, as the static pressure does not vary greatly under with external conditions, whereas a float would be bounced around.

A mechanical (vertical) float switch is attached to a thin rod, which is attached to a floater; when the water level rises, the float rises with it, which in turn lifts the rod. This movement triggers the pump motor to activate and pump out the water. As the water level drops, the floater moves with it, which pulls down the rod and deactivates the motor.

A wide angle float switch has a floating ball connected on a cord that rests on the surface of the water; as the water level rises, the float rises accordingly, pulling on the cord. When the cord is taut, it pulls the switch, which activates the sump pump. It is important to clean the float switch regularly, as dirt may accumulate in and around the float. Should enough dirt build up, the float will be weighed down in the water, unable to rise with the water level, which will prevent it from activating the sump pump.

Sizing

To properly size a sump pump, it is necessary to first ascertain the system capacity and the total dynamic head required.

System capacity is the number of gallons which flow into the sump basin per minute. It is imperative that the sump pump can expel water from the basin faster than water flows into it. Determining the in-flow may be done by placing a ruler into the basin during a heavy rain, and measuring how many inches of water accumulate within 60 seconds. This can be translated into the system capacity. In an 18-inch diameter basin, 1 inch of water is equivalent to 1 gallon; in a 24-inch diameter basin, 1 inch is more closely correlated to 2 gallons. So if 18 inches of water accumulate in a small sump basin within 60 seconds, and each inch is equivalent to a gallon of water, then the system capacity is 18 gallons per minute (GPM).

Total dynamic head is the sum of the static head (vertical lift) and the friction head. The static head is simply the distance between the point at which water enters the pump, and the point where the discharge pipe becomes horizontal, at the highest point in the discharge piping. So if the vertical distance from the water entry point to the point where the discharge pipe becomes horizontal is 13 feet, then that is the static head. The friction head is a bit more complicated: it is the “equivalent length of pipe” plus the actual length of pipe multiplied by the loss due to friction, and then divided by 100.

• To determine the equivalent length of pipe, the lengths of all the pipe fittings required for a given system are added together. For example, in Table A below, for a 1-1/4 inch pipe, three 90-degree elbows and one check valve give a total equivalent length of 22 feet.
• The actual pipe length is what runs horizontally from the house, which should be visible at the pipe’s point of discharge from the house. For this example, let the actual length equal 100 feet.
• Friction loss is a measure of how much the flow of water through the pipe is slowed by the force of friction; this depends on both the size of the pipe and the GPM of water moving through the pipe. Using the previously determined system capacity as the GPM in Table B, if the flow is 18 GPM through the 1-1/4 inch pipe from the previous example, then the loss due to friction is 5.25 per 100 feet of pipe.
• To determine the friction head, the actual length (in this case, 100 feet) and the equivalent length (22 feet) are added together, then multiplied by the friction loss (5.25) and divided by 100. So, (100 + 22)(5.25)/100 = 6.4 feet.
• The total dynamic head, then, is the sum of the static head (13 feet) and the friction head (6.4), which for this example is 19.4, but should be rounded up to 20 feet.

Using the system capacity and the total dynamic head, the final step is to consult a pump curve. A pump curve is unique to every type of pump, and illustrates the GPM a particular pump can produce for a given head. It is important to select the sump pump that best matches the calculated GPM and head height; otherwise the pump may be either too small or large for the required application. A too-small pump won’t be able to expel the water flowing into the sump pit, whereas an over-large pump will expel the water too quickly, resulting in a short cycle (when the pump starts and stops too often), which can reduce the life of the sump pump.

Applications

Sump pumps are generally installed either within or above a collecting pit (sump pit). They can be used in a wide variety of applications, from light-duty water transfer to heavy-duty high temperature applications. These pumps are designed only for the pumping of ground water, and are not designed to pass solids larger in diameter than fine soil. Sump pumps are intended for intermittent, not continuous use.

Draining accumulated water

Sump pumps are commonly used for pumping accumulated rain or ground water from a collecting sump pit to municipal storm drains or dry wells.

Dewaterin

g flooded basements

These pumps can also be used for draining basements, or ground floors which experience regular flooding or dampness.

Commercial and industrial applications

Sump pumps are also applicable in commercial and industrial settings, such as loading docks, construction and excavation sites, and many more.