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Home / Technical Information / Pumps Technical Data / Septic Tank Pumps Technical Data / Submersible Sewage Pumps FAQ

Submersible Sewage Pumps FAQ

Questions & Answers

The submersible wastewater pump is a centrifugal pump consisting of a rotating impeller working inside a stationary casing, or volute. Its job is to pump wastewater uphill to a collection or receiving station. The pump motor turns the impeller, which transfers velocity to the liquid which surrounds it. This liquid is collected by the pump casing, and directed to the discharge of the pump. The submersible wastewater pump differs from normal centrifugal pumps in that solids must be able to pass through the pump. This requires special open or “non-clog” impeller designs, as well as sufficient clearance between the impeller and the wall of the casing.
No. A system should be sized to the pump performance not the horse power. A larger pump could cause to much pressure for the system. The pump size should be based on the performance of the pump, not its horsepower rating.
For a single float you simply adjust the tether length of the switch to achieve the proper pumping range. For a two-float installation, you would adjust the distance between the floats.
Although not recommended, it can be done if the proper voltages are being connected, i.e.: 120 volt current to 120 volt switch. Wrong voltages could lead to failures if there are electronic parts in the circuit.
This is a violation of the National Electrical Code.
The cable used on float switches is not rated for direct burial. Therefore, it should not proceed beyond the junction box unless it is inside a conduit.
No. Sewage pumps are designed to operate for short periods of time. Running a sewage pump for too long can cause the pump to overheat. Sewage pumps are filled with oil, the pump seal fails due to fish waste or because the motor overheated the oil will be discharged into the water feature and kill the fish and plants. When the motor cools water will be drawn into the motor cavity and “burn “the motor windings.. Using a sewage pump in any kind of water circulation application, will void the warranty.
Yes, but the pipe size should not be reduced smaller than the pump solids passing capabilities. Reducing the pipe will increase friction causing the flow rate to decrease. The pipe size depends on the system requirements. Generally, the minimum diameter pipe size is 1 1/2” for effluent pumps but local codes may dictate pipe size.
Refer to local codes. A smaller basin will hold less water per inch causing the pump to cycle more often. We recommend using a 18" diameter basin.
The air vent hole allows air trapped under the check valve to escape. A symptom of not having an air vent would be the pump runs but no water is being discharged.
We suggest that you install the check valve in a horizontal (side-to-side) position instead of vertical (up-and-down). When the pump shuts off, the solids and liquid in the pipe can settle back against the check valve. If solids settle on top of a check valve flapper in a vertical position, it is possible for the solids to prevent the valve from opening again. . This will cause the pump to run without discharging the waste. The pump will damage itself, and sewage or effluent will back up.
No. Sewage pumps are designed to operate for short periods of time. Running a sewage pump for too long can cause the pump to overheat. Sewage pumps are filled with oil, the pump seal fails due to fish waste or because the motor overheated the oil will be discharged into the water feature and kill the fish and plants. When the motor cools water will be drawn into the motor cavity and “burn “the motor windings.. Using a sewage pump in any kind of water circulation application, will void the warranty.
Most sewage pumps com with a 20 foot cord as standard. If there is no outlet near the sewage pit, we suggest that you have an outlet installed there by a professional electrician.
Sewage and effluent pumps are designed to pump things that usually go down a residential drain. Sewage pumps not tested with other liquids so we cannot say whether they will be chemically compatible with what you need to pump. Sewage/effluent pumps should not be used for anything other than residential sewage or effluent applications. Never pump anything flammable!
It is not possible for us to maintain lists of “qualified” people that we could recommend. You would need to check your local “Yellow Pages” etc. for qualified an competent people.
Two reasons: (1) to keep the pump partially or fully submerged and (2) to provide for an adjustable pumping range for proper dosing.
Pumps rated for effluent applications usually have a solids size rating of 1/2" to 3/4" spherical diameter.
This depends on the application and proper system design. Septic systems that are too small, abused by using strong caustic drain openers, and improperly maintained can cause significant reduction in the pump’s life.
Pumps that are rated as “Sump/Effluent” by the manufacturer can be used in the septic system. Only a pump specified as being suitable for effluent or sewage should be used in a septic system.
Most codes require a check valve and a ball valve to be installed on the discharge line of each pump in the system. If the total volume of liquid capable of draining back into the pump chamber is greater than approximately 25% of the volume the pump will cycle. When a check valve is installed, all piping must be below the frost line. As always, consult your local codes.
We do not sell parts….Installation and parts manuals are provided only as reference tools. Neither the manufacturer nor King Pumps makes any representation or warranty of any kind to the Buyer that he or she is qualified to neither install nor make any repairs to the product. In fact, the manufacturer and King Pumps expressly state that installation, repairs and parts replacements should be undertaken by qualified and competent technicians or contractors and not by the Buyer. The Buyer assumes all risk and liability arising out of his or her installation or repair to the original product.
Some sump, sewage, and utility pumps have a tag attached near the end of the power cord that shows the pump’s model number and date code. The date code will be marked as “date code”, “code”, or “MOD”. Also, all pumps have an information label on the pump that has the model number and date code on it. Date code is usually a combination of letters and numbers.
A. residential pumps labeled for “sewage” can pass up to 2” solids. A pump labeled as an “effluent” pump can handle up to ¾” solids. Commercial sewage pumps will pass 3” solids of more depending on the discharge size.
“Solids” do not mean things like bolts and stones. “Solids” mean things that can be broken up by human hands and that normally can be flushed down a toilet. Most sewage pumps have a thermoplastic impeller that could be damaged by very hard items.
No, a “grinder” pump has an impeller that is made like blades. It can cut up, or grind up the sewage being passed through it. Sewage solid handling pumps do not that. They are called “solids handling” pumps since they simply pass the solids through mostly intact.
Never use a smaller diameter pipe than the size of the pump’s discharge. Use minimum 2” pipe. You might have to use larger diameter pipe if you have to push a long distance. Be careful with this though. See the next question. . . . .
If a pipe of too large a diameter is used, the flow rate of the discharge can be too slow. This can cause the solids to settle out and lay in the pipe. Over time, the sludge that builds up will cause blockages in the pipe. The minimum flow rate of sewage and other liquids containing solids is 3 feet per second. If you are designing a sewage run for your home, consult an engineer for help in determining proper pipe sizes.
DO NOT use an extension cord. It is MUCH better to plug the pump into a dedicated outlet that is fed by a circuit breaker or fuse that feeds power ONLY to that outlet. This ensures that the pump will receive proper voltage. If there is no outlet near the sump pit, we suggest that you have one installed there by a professional electrician.
The main difference is the size of the solids in the liquid. Effluent is any liquid that has gone down a residential drain. It can contain solids up to ¾” in size. This is normally considered to be water containing soap, laundry discharge, water from sinks, etc. Sewage has also gone down a residential drain but can contain solids up to 2” in diameter.
Most sewage pumps come with a tethered-style float switch for their efficient operation... You can use a vertical-style switch but the solids contained in sewage & effluent can block the operation of a vertical-style switch. The contents of sewage and effluent can coat the contacts of an electronic-type switch and prevent that from working very long.
No. Feminine products should not be flushed when a sewage pump has to handle that. Sewage pumps can have problems passing those items and could jam. The Liberty grinder pump will handle feminine products.
You need to know the amp draw of the pump and multiply that by the voltage to get the watt usage of the pump. Example: Pump draws 5 amps on 115 volts. 5amps x 115volts = 575 watts. Give this information to the Generator supplier to size the right product. An AC motor can draw three to five times its regular amp draw for about ½ second when it starts up. So to run our example pump, we need a generator that can supply a startup surge of at least 2875 watts (575 x 5) and can continue to supply the 575 watts as the pump runs. This is accurate if the pump is the ONLY thing the generator is going to supply power for. If you also want to run lights, etc. then that needs to be added to the generator size. You should contact a Generator Supplier for the final selection.
This depends on the application and proper system design. Septic systems that are too small, abused by using strong caustic drain openers, and improperly maintained can cause significant reduction in the pump’s life.
To keep the pump partially or fully submerged and to provide for an adjustable pumping range for proper dosing.
Pumps that are rated as “Sump/Effluent” by the manufacturer can be used in the septic system. Only a pump specified as being suitable for effluent or sewage should be used in a septic system.
The depth of your pump will depend on your local codes. Because of the gases involved with septic tanks, we recommend keeping the pump completely submerged. This will prevent the gases from attacking the watertight gaskets.
The function of the wastewater system is to receive and collect used water, store it temporarily, and move it to a collection system. A wastewater system is often called a sewage system, a lift station, or a pumping station. They usually consist of a submersible wastewater pump and other equipment necessary to receive wastewater and move it to a collection station.
Residential (Urban/Rural) : ALL contaminated water is drained into the basin, which is then pumped to a gravity sewer system. Mound System (STEP - Septic Tank Effluent Pump): Effluent from the septic tank being pumped to a “mound,” or leachfield. Local codes may require this type of system. Or it can be used where the homeowner desires a better distribution of effluent across the drainage field. Sewage Lift Station: Sewage lift station, equipped with one sewage pump, lifting sewage to a gravity feed collection system. Municipal and Commercial Sewage Station: Sewage station, designed for heavy duty service.
Submersible Water Pump; Basin ; Basin Cover; Vent; Electrical Controls; Check Valve (Swing Check); Shut-off valve (s); Inlet Hub; Discharge connection; Float Switch(s) ; Float Switch Bracket; Interconnecting piping and wiring
When sizing any wastewater system, first determine the size of the solids the system will be handling. This may determine the type of pump you will need to use.
Submersible wastewater pumps are generally classified by the nature of the wastewater and the size of solids they are capable of handling, as follows: Sump Pumps: 3/8” solids. Generally dirty water, solids not typically present. Effluent Pumps: Less than 1” solids. Partially or completely treated wastewater flowing out of a septic tank or treatment plant. Sewage Pumps (Residential): 2” solids. Household wastewater which may contain human waste. Sewage Pumps (Municipal and Commercial): 3” and larger solids. Municipal or commercial wastewater. Grinder Pumps: Grinder Pumps are specialty pumps designed for applications where a gravity system is not practical. They are equipped with hardened stainless steel cutters which cut solids into small pieces, so the resulting residue can be pumped under pressure through smaller diameter piping. These can be part of a pressure sewer system. Solids-Handling requirements may be determined by local codes and/or by the type of application and types of solids.
A residential sewage pump should have the capacity of handling spherical solids of at least 2” diameter; commercial sewage pumps should have the capacity of handling spherical solids of at least 3” diameter
“Solids” do not mean things like bolts and stones. “Solids” mean things that can be broken up by human hands and that normally can be flushed down a toilet. Most sewage pumps have a thermoplastic impeller that could be damaged by very hard items.
The submersible wastewater pump is a centrifugal pump consisting of a rotating impeller working inside a stationary casing, or volute. The pump motor turns the impeller, which transfers velocity to the liquid which surrounds it. This liquid is collected by the pump casing, and directed to the discharge of the pump. The submersible wastewater pump differs from normal centrifugal pumps in that solids must be able to pass through the pump. This requires special open or “non-clog” impeller designs, as well as sufficient clearance between the impeller and the wall of the casing. Do you use single or double pumps in wastewater systems? Most residential wastewater systems are simplex or single-pump systems. However, some residential/systems and most municipal and commercial systems are duplex or two-pump systems. (Larger municipal and commercial systems may use three or four pumps.)
A simplex system uses only one pump. In a simplex system, wastewater flows into the receiver basin through an inlet pipe. As the basin begins to fill, a switch floats up and turns on the single pump. As the pump evacuates the system the wastewater level in the receiver basin falls until the switch turns the system off.
A duplex system typically uses a three or four switch system to divide the pumping between the two pumps. If a pump fails to turn on in the proper sequence, a switch will turn on the other pump and sound an alarm in a three switch system. In a four switch system the top switch sounds the alarm. The duplex system divides the pumping load between the two pumps and provides backup in case of failure. For this reason each pump and discharge pipe in a duplex system is sized to handle the maximum anticipated flow. Both pumps in a duplex system are placed in the same basin. When sizing a duplex system, make sure that each pump and discharge pipe is sized to handle the total load.
The period of time from when the pump switches on until it switches off is called a cycle, or cycle time. If a pump turns on and off (cycles) too frequently, there is a risk of motor damage from overheating. A properly sized pump should cycle within manufacturer’s recommendations for proper cooling.
The amount of wastewater pumped per cycle is called drawdown. When this drawdown is being distributed throughout an absorption field, it is also called a “dose,” as in “dosing” the field, or applying the maximum “dosage.” In many areas, “dosage” amounts and maximums are dictated by Local Codes. Be sure to check with the appropriate agencies.
To calculate drawdown you must first determine switch ON and OFF locations. Then multiply the distance between the ON and OFF locations times the basin capacity in gallons per inch to get Total drawdown or Usable Volume.
The ON level switch (or uppermost) should be set a minimum of 3” below basin inlet. The OFF level switch should be set 6” below top of pump dome.
The RULE OF THUMB for Basin Capacity in Gallons/Inch is as follows: 24 " Basin Diameter = 2 Gallons per inch of depth; 30 " Basin Diameter = 3 Gallons per inch of depth; 36 " Basin Diameter = 4 Gallons per inch of depth; 42 " Basin Diameter = 6 Gallons per inch of depth; 48 " Basin Diameter = 8 Gallons per inch of depth; 60 " Basin Diameter = 12 Gallons per inch of depth; 72 " Basin Diameter = 18 Gallons per inch of depth ; What is the formula to compute drawdown? Total Drawdown or Usable Volume = Distance between On and Off Switch(in inches) x Capacity in Gallons/Inch
A number of factors are involved; including number of people, bathrooms, and plumbing fixtures, as well as total water consumption. Flow can vary widely; the average per capita flow varies from 50 to 500 gallons per day. There are also peak periods of use, usually in the morning and the evening when the family is at home. System capacity must be sufficient to handle maximum anticipated peak flow. One method of calculating system capacity (called the “Fixture Method”) is to calculate the number of plumbing fixtures, assign a value to each, and then divide by a pre-determined factor to arrive at the required system capacity.
An easy-to use rule of thumb, which is practically foolproof: 1 BATHROOM - 20 GPM; 2 BATHROOMS - 30 GPM; 3 BATHROOMS - 40 GPM; 4 BATHROOMS - 50 GPM; 5 BATHROOMS - 60 GPM; 6 BATHROOMS - 70 GPM
A wastewater pump must o maintain sufficient velocity to scour or clean the walls of the pipe so the pipe doesn’t get clogged from buildup. The capacity or flow of the pump produces the velocity which scours the line. Minimum velocity needed to scour the line is 2 ft. per second.
The required flow to maintain minimum velocity of 2 feet per second is: 1-1/4” PIPE - 9 GPM; 1-1/2” PIPE - 13 GPM; 2” PIPE - 21 GPM; 2-1/2” PIPE - 30 GPM; 3” PIPE - 46 GPM; 4” Pipe – 78 GPM; There may be State or Local Codes requiring a minimum sanitary or plumbing system capacity based on usage and/or occupancy. Required system capacity can vary widely depending upon family ages and lifestyle. Be sure to check with the appropriate agencies.
More horsepower or flow is not always better – especially in smaller basins. Short cycling may reduce the life of the pump. A longer pumping cycle will be better for pump longevity. The most efficient part of the curve is usually in the middle of the curve, away from maximum head or flow
The Total Dynamic Head is the pressure the pump must overcome to lift the liquid from the pump to the highest point in the system (vertical elevation or static head), plus the pressure required to push the liquid through all the pipe and fittings (friction loss or friction head), plus any system pressure requirements. Total Dynamic Head (or Total Head) is the pressure the pump must provide to do the job. The Total Dynamic Head can be expressed in feet of head or in pressure (pounds per square inch or PSI).
To convert PSI to feet of head, multiply by 2.31; To convert feet of head to pressure, divide by 2.31.
Total Dynamic Head (TDH) = Vertical Elevation (Static Head) + Friction Loss + System Pressure Requirements. What is the systems vertical elevation? Vertical Elevation is the distance from the pump inlet to the highest point in the discharge system.
As the wastewater is pumped from the receiver basin to the collection points the inside of the pipe and fittings provide a resistance called friction. Friction loss works against pump performance, so you want to keep it as low as possible.
Friction loss INCREASES as pipe length increases. The longer the pipe, the more the friction loss in the system. Friction loss INCREASES as flow rate increases. The greater the flow rate the greater the friction loss. Friction loss DECREASES as inside pipe diameter increases. The larger the inside diameter of the pipe, the less the friction loss in the system. Therefore, you can reduce friction loss by using a larger diameter pipe. Are there published pre-calculated Friction Loss Tables? Yes, there are published pre-calculated Friction Loss Tables available for different flow rates and different types of fittings. When calculating Friction Loss, always round UP to the nearest whole foot. See our Technical Information Section.
This is the pressure required or available at the end of the pipe as the wastewater enters the tank or collection site. These pressure requirements are often dictated by Local Codes
They always TAKE PRECEDENCE OVER other methods of sizing and selection, including the information found in this tutorial. State and Local Codes often contain system or size requirements based on local soil conditions and/or lot layout including Dosage Requirements.
The size of the solids will determine whether the application requires a sump, effluent, or sewage pump. Sump - 3/8” solids (solids typically not present); Effluent - Less than 1" solids; Sewage (residential) - 2" solids ; Sewage (municipal and commercial) -3"+ solids; Grinder - Specialty pumps used in pressurized systems. What is the capacity required in a wastewater system? Capacity Required is the flow or discharge capacity required by the installation.
While flow can vary from installation to installation, these RULE OF THUMB: will handle most situations: 1 BATHROOM - 20 GPM; 2 BATHROOMS - 30 GPM; 3 BATHROOMS - 40 GPM; 4 BATHROOMS - 50 GPM; 5 BATHROOMS - 60 GPM; 6 BATHROOMS - 70 GPM; When in doubt, always select a pump with capacity greater than anticipated peak flow.
Basin must be large enough to accommodate the pump, with room for the switch (es) to swing freely. Must provide adequate drawdown to assure at least minimum run times (cycle times) for proper motor cooling. • Basin must provide adequate run time and flow volume to evacuate (turn) the liquid stored in the discharge pipe at least once per ON/OFF cycle.
The time the pump runs during one complete on and off cycle.
To calculate run time divide drawdown by pump capacity.
Minimum run time of one minute for motors through 1-1/2 hp, and two minutes for larger pumps.
In determining Evacuation you must check calculate how much water is in the discharge pipe (stored discharge volume). Multiply the length of discharge pipe (vertical elevation plus horizontal run) by the pre-calculated Stored Discharge Volume. 1-1/4" pipe - .06 Gallons per Foot;1-1/2" pipe - .09 Gallons per Foot ; 2" pipe - .16 Gallons per Foot ; 3" pipe - .36 Gallons per Foot; 4" pipe - .652 Gallons per Foot; 6" pipe - 1.4 Gallons per Foot.
Basin must provide adequate run time and flow volume to evacuate (turn) the liquid stored in the discharge pipe at least once per ON/OFF cycle. To determine how many times the system will evacuate (turns) the wastewater stored in the discharge pipe per ON/OFF cycle: Divide the Drawdown by the Stored Discharge Volume I there a quick way to determine the size of the basin? The RULE OF THUMB is that the Receiver Basin should be at least 2 1/2 – 3 times pump capacity. Local codes and regulations often dictate the minimum size of the Receiver Basin.
The discharge pipe must be capable of handling the size of solids in the system, and be at least as big as the pump outlet. The size of the piping (and fittings) will also affect Total Dynamic Head The larger the inside diameter of the pipe, the less the friction loss. The size of the piping will also affect the scouring velocity of the system The required flow to maintain minimum velocity of 2 feet per second is 1-1/4” PIPE - 9 GPM; 1-1/2” PIPE - 13 GPM; 2” PIPE - 21 GPM; 2.5” PIPE - 30 GPM; 3” PIPE - 46 GPM; 4” Pipe – 78 GPM
All electrical installations must comply with the National Electrical Code and all applicable Local Codes and ordinances. Submersible wastewater pumps are designed to run on single phase or three phase electrical service. Single phase circuits provide 115, 208 or 230 volts. Three phase circuits provide 200, 230, 460 or 575 volts. The power company usually establishes the type of service available. The available power supply must match the power supply required by the pump (see pump nameplate. A separate, properly grounded circuit must be provided for the pump. Pump motors that use three-phase service require “heaters,” or overload protection devices. Most single phase motors have built-in thermal protection. Larger models may require an overload connection in the panel. Pump motor and controls must be the same voltage, phase, and frequency as the available electrical service. Who is NEMA and what are NEMA’s control panel ratings? NEMA (National Electric Manufacturers Association) rates control panel enclosures for weather resistance. NEMA 1 - General purpose. For normal indoor service conditions; NEMA 3R - Rain tight; NEMA 4 - Water tight; NEMA 4X - Water tight. Corrosion resistant; NEMA 12 - Industrial use.
Pump Rated Float Switches provide automatic operation of the system by directly controlling the pump motor. Wide angle - Mechanically controlled with piggyback plugs or bare leads; Dual float - with holding relay with piggyback plugs or bare leads ; Pressure activated with piggyback plugs or bare leads ; Piggyback plugs. The piggyback float switch plugs into the main power supply,; and the pump power cord “piggybacks” into the switch plug. In case of switch problems the piggyback switch can be removed for replacement and the pump power cord plugged into the main power supply for temporary manual operation.
Control switches are provided with bare leads for direct connection to a control panel Control float switched are not rated for directly controlling a pump motor. Mechanically controlled - Narrow Angle; Normally Open / Normally Closed - Narrow Angle

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