What is a Sump Pump?
are pumps used for drainage that removes accumulated water from a sump pit or other location. A sump pit, commonly found in the home basement, is simply a hole dug in the ground to collect water. The water may enter via perimeter drains funneling into the pit, or may arrive from natural ground water in the earth.
How are sump pumps typically used?
Sump pumps are installed particularly where basement flooding is seen as a problem, but are also used to ameliorate dampness by lowering the water table under the foundation. Sump pumps pipe water away from the house to any place where it no longer presents a hazard, such as a municipal storm drain or dry well. Older properties may have their sump pumps connected to the sanitary sewer, but this is frowned upon now (and may be against the plumbing code) because it can overwhelm the municipal sewage treatment system. Though in some cases, a sump pump is used when a lower floor is below the sewer lines, to pump greywater or blackwater waste from that floor to the lines.
What types of sump pumps are available?
There are two available categories of sump pumps, Automatic and Manual. An automatic sump pump has a switch attached that activates the pump when the water reaches a certain height and turns the pump off when the sump pump has drained the water. A manual sump pump must be turned on and off manually. Sump pumps may also have battery backups, control panels, and automatic switches amongst other accessories installed to ensure continuous and proper operation.
Selecting a Sump Pump
The selection of a sump pump will rest heavily on the application in which it will be used. To select the appropriate sump pump consider the following:
- Automatic vs. Manual Operation: Selection of a manual sump pump means that you will turn the pump on and off when appropriate. Selecting an automatic sump pump means that a switch is wired to the sump pump to turn it on or off at appropriate water levels. Automatic switches include pressure switches, low level pressure switches and float switches.
- Horsepower: Sump pump horsepower will vary from 1/4 horsepower to multiple horsepower.
- Head Pressure: The head pressure of a sump pump describes the maximum height that the pump will move water. For instance, a sump pump with a 15’ max head (also called a shutoff head) will pump water up 15’ before it completely loses flow. Technically, head pressure is defined as an expression of a pressure in terms of the height of fluid; P = ypg, where p is fluid density and y is the fluid column height. Other considerations may be added to overall head pressure, including loss from elbows/bends and friction loss from long horizontal runs.
- Cord Length: The cord length of a sump pump describes the length of the power cord. It is also important to consider the length of the cord of any special switches that may be connected to your pump.
- Phase & Voltage: Sump pumps are available in single and three phase. The voltages offered include 115, 230, and 460 volt.
- Backup System & Alarm: If redundancy and an alert system are vital for operation of your sump pump, consider a backup system and/or alarm.
Sump Pump Replacement
First make sure the pump is disconnected from the electric power source before you handle or clean it.
This is a very easy Do-it-Yourself project. Pump manufactures have developed products that minimize complicated procedures.
- Match HP (motor horsepower) with the previous model most pumps have a manufactures’ tag or label that provide this information and the model number.
- Determine and match the discharge pipe size.
- Determine and match the correct length electrical cord.
New Sump Pump Installation
The following instructions are general instructions for basic sump pump installation. Always follow the manufacturer's installation instructions.
- Know that your sump pit must also accommodate a control such as a vertical float switch or tethered float switches. Larger pits can accommodate both.
- Horse power can be determined by how high and how fast you want to pump the water.
- The electrical outlet should be near enough for the manufactures electric cord to reach without an extension.
- Typical submersible sump pumps have a three-pronged, grounded plug and a 115-volt, 60 cycles, single-phase motor with overload protection. A three-wire grounded receptacle is needed above the floor near your sump.
- For greater pump performance or certain existing electrical service other motor electrical detailed wiring is convenient. Example; 230 or 460 volt and 3 phase.
- A check valve is always recommended on the discharge pipe to prevent water from returning into the sump pit. When a check valve is used, drill a relief hole (1/8" or 3/16" diameter) in the discharge pipe. This hole should be located below the floor line between the pump discharge and the check valve. Unless such a relief hole is provided, teh pump could "air lock" and not pump water event though it will run.
- A basin with lid can help organize the various inlet piping, outlet piping and electrical cords.
- Alarms can be added to alert in the event of pump or electrical failures.
- An Automatic Sump Pump Back-Up System provides extra protection in the event the primary sump pump fails, an obstruction in the sump pit blocks flow, or a power outage occurs. It will also function as an alarm system if the primary pump fails to empty the sump pit.
Reading a Pump Curve
A pump curve tells you the flow performance (measured in gallons per minute or liters per minute) of a pump relative to the head pressure. To read a pump curve, you must first examine the units of measurement used along each of the displayed axes. The pictured pump curve displays head pressure in Feet (along the left-side y-axis) and in Meters (along the right-side y-axis). Increased head pressure is indicated as you travel up the y-axis. The flow performance is indicated in gallons per minute (along the lower x-axis) and liters per minute (along the upper x-axis). This is an indication of the output flow of a pump.
The pump curve is read by first determining the head pressure of the application in which the pump will be used. Once you’ve determined your head pressure, simply follow the head value you have selected from the y-axis horizontally to where it intersects with the pump curve line. From that point, move vertically to the flow measurement on the x-axis.
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