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In recent months I have received a number of inquiries about how to install a laundry sink, shower stall, water closet of bathroom group in a basement where the house drains are elevated above the floor and you cannot achieve drainage by means of gravity flow.
Whenever the fixture drain outlet is below the elevation of the house drains we obviously must have some means of pumping the waste vertically before discharging into the gravity flow house drains. Some have suggested that we might drain a laundry tub or shower stall into a sump pit then use a sump pump to lift the water up to the drains, but that method is strictly prohibited by the plumbing codes. Sump pumps are to be used solely to discharge storm drainage and in no case may a sump pump be be used to convey sanitary waste or connected directly to a sanitary drain.
In its basic configuration a Sewage Ejector Pump assembly appears quite similar to a submersible sump pump & sump pit assembly, however there are some very distinct differences. (See the attached illustration)
The sewage ejector sump pit must be fitted with a removable water tight cover.
The sewage ejector pit must have a dedicated vent through the roof and the vent may not be combined with any other vents in the structure.
The Sewage Ejector control float must be adjusted so that the lowest line discharging into the pit will remain a minimum of 2" above the highest level of liquids in the sump.
While a sump pump is only designed to pump water, by necessity a sewage ejector pump must be capable of passing some suspended solids, especially if serving a water closet. To this end Under both the International Residential Code(IRC) and the Uniform Plumbing Code (UPC) the discharge line from a sewage ejector pump must be a minimum of a 2" diameter line except, the IRC will permit the discharge line to be a minimum of 1-1/4" if the pump is equipped with a macerator grinder. (A macerator grinder is an optional built in cutter mechanism similar to a garbage disposal).
The vertical discharge line MUST BE equipped with a "Backwater valve" and it must also have a manually operated "Gate Valve" above the backwater valve. The purpose of the gate valve is to be able to manually close the line to permit servicing the backwater valve or the pump assembly.
The Ejector Pump discharge line must rise vertically to a point higher than the horizontal gravity flow drain to which it will discharge into. The connection to the gravity flow line must be made by means of a Wye fitting in the Gravity line with the side opening of the Wye oriented in a vertical position.
Some local jurisdictions also require that a sewage ejector pump system be equiped with either a flashing light or audible alarm to indicate if the pump malfunctions.
SIZING THE PUMP:
Sewage ejection pumps come in a very broad range of sizes from a small single fixture pump built into an upflush toilet up to super large 24" diameter or greater systems used on municipal sewer mains.
In order to determine what size of pump you need you would first begin with a list of all fixtures that will be discharging into the sewage ejector pit. Using the standard DFU (Drainage Fixture Unit) tables published in the code book we first determine the total DFU load for the sewage ejector, then select a pump suitable to the load however, the codes have established a minimum allowable size of the pumps.
The IRC sets the minimum at 14.2gal/min and the UPC minimum is 20gal/min.
Selecting the point where we intend to connect the discharge from the Sewage Ejector Pump to the house gravity drain system can be rather complex. Many people are under the false assumption that since the discharge line from the pump is only 2" that we could connect to any line 2" or greater, but such is not the case. We must remember that the discharge from the sewage ejector is under a constant positive pressure from the pump but once it enters the regular house drains it will need to flow by gravity, therefore the gravity line will need to be much larger.
All Drain, Waste & Vent lines are sized by the DFU method. Once we know the DFU load at any given point in a Drain & waste system we can then determine the required size of the line from the line sizing tables published in the code.
When connecting a Sewage Ejector we must begin by determining the DFU load created by the ejector pump.
The IRC requires that we compute the DFU load by allowing 1.5DFU's for each gallon per minute flow rate from the pump. Considering that the code minimum pump size was 14.2gal/min and allowing 1.5DFU per GPM the minimum DFU load from a sewage ejector pump would be 14.2 x 1.5 = 21.3DFU
The UPC sets the pump minimum at 20gal/min and the DFU conversion at 2DFU per gallon of flow so the UPC minimum is 20 x 2 = 40DFU
Before connecting into a drain line we must also determine the existing DFU load on that line, then add the pump DFU load to the existing load to get the total combined load.
As I stated earlier, do not let the small diameter of the pump discharge line fool you. Under the IRC a 3" diameter horizontal branch line run with a 1/4" per foot pitch is limited to a maximum of 20 DFU. As you can see at 21.3DFU the pump discharge alone would exceed the maximum limit for a 3" branch line not to mention the existing load on the 3" branch.
Under the IRC a 3" main drain is permitted up to 36 DFU's however the main drain already has the total DFU load for all fixtures in your house so here again, in many cases it would not be permitted to connect the ejector pump to this line. In most cases if your house currently has a 3" main drain and sewer line in order to legally install a sewage ejector pump system it would require changing the entire house drain down stream of the pump input, as well as the house sewer line, which is the underground line from your structure to the municipal main or septic tank from the current 3" diameter to a 4"dia.
Whenever the fixture drain outlet is below the elevation of the house drains we obviously must have some means of pumping the waste vertically before discharging into the gravity flow house drains. Some have suggested that we might drain a laundry tub or shower stall into a sump pit then use a sump pump to lift the water up to the drains, but that method is strictly prohibited by the plumbing codes. Sump pumps are to be used solely to discharge storm drainage and in no case may a sump pump be be used to convey sanitary waste or connected directly to a sanitary drain.
In its basic configuration a Sewage Ejector Pump assembly appears quite similar to a submersible sump pump & sump pit assembly, however there are some very distinct differences. (See the attached illustration)
The sewage ejector sump pit must be fitted with a removable water tight cover.
The sewage ejector pit must have a dedicated vent through the roof and the vent may not be combined with any other vents in the structure.
The Sewage Ejector control float must be adjusted so that the lowest line discharging into the pit will remain a minimum of 2" above the highest level of liquids in the sump.
While a sump pump is only designed to pump water, by necessity a sewage ejector pump must be capable of passing some suspended solids, especially if serving a water closet. To this end Under both the International Residential Code(IRC) and the Uniform Plumbing Code (UPC) the discharge line from a sewage ejector pump must be a minimum of a 2" diameter line except, the IRC will permit the discharge line to be a minimum of 1-1/4" if the pump is equipped with a macerator grinder. (A macerator grinder is an optional built in cutter mechanism similar to a garbage disposal).
The vertical discharge line MUST BE equipped with a "Backwater valve" and it must also have a manually operated "Gate Valve" above the backwater valve. The purpose of the gate valve is to be able to manually close the line to permit servicing the backwater valve or the pump assembly.
The Ejector Pump discharge line must rise vertically to a point higher than the horizontal gravity flow drain to which it will discharge into. The connection to the gravity flow line must be made by means of a Wye fitting in the Gravity line with the side opening of the Wye oriented in a vertical position.
Some local jurisdictions also require that a sewage ejector pump system be equiped with either a flashing light or audible alarm to indicate if the pump malfunctions.
SIZING THE PUMP:
Sewage ejection pumps come in a very broad range of sizes from a small single fixture pump built into an upflush toilet up to super large 24" diameter or greater systems used on municipal sewer mains.
In order to determine what size of pump you need you would first begin with a list of all fixtures that will be discharging into the sewage ejector pit. Using the standard DFU (Drainage Fixture Unit) tables published in the code book we first determine the total DFU load for the sewage ejector, then select a pump suitable to the load however, the codes have established a minimum allowable size of the pumps.
The IRC sets the minimum at 14.2gal/min and the UPC minimum is 20gal/min.
Selecting the point where we intend to connect the discharge from the Sewage Ejector Pump to the house gravity drain system can be rather complex. Many people are under the false assumption that since the discharge line from the pump is only 2" that we could connect to any line 2" or greater, but such is not the case. We must remember that the discharge from the sewage ejector is under a constant positive pressure from the pump but once it enters the regular house drains it will need to flow by gravity, therefore the gravity line will need to be much larger.
All Drain, Waste & Vent lines are sized by the DFU method. Once we know the DFU load at any given point in a Drain & waste system we can then determine the required size of the line from the line sizing tables published in the code.
When connecting a Sewage Ejector we must begin by determining the DFU load created by the ejector pump.
The IRC requires that we compute the DFU load by allowing 1.5DFU's for each gallon per minute flow rate from the pump. Considering that the code minimum pump size was 14.2gal/min and allowing 1.5DFU per GPM the minimum DFU load from a sewage ejector pump would be 14.2 x 1.5 = 21.3DFU
The UPC sets the pump minimum at 20gal/min and the DFU conversion at 2DFU per gallon of flow so the UPC minimum is 20 x 2 = 40DFU
Before connecting into a drain line we must also determine the existing DFU load on that line, then add the pump DFU load to the existing load to get the total combined load.
As I stated earlier, do not let the small diameter of the pump discharge line fool you. Under the IRC a 3" diameter horizontal branch line run with a 1/4" per foot pitch is limited to a maximum of 20 DFU. As you can see at 21.3DFU the pump discharge alone would exceed the maximum limit for a 3" branch line not to mention the existing load on the 3" branch.
Under the IRC a 3" main drain is permitted up to 36 DFU's however the main drain already has the total DFU load for all fixtures in your house so here again, in many cases it would not be permitted to connect the ejector pump to this line. In most cases if your house currently has a 3" main drain and sewer line in order to legally install a sewage ejector pump system it would require changing the entire house drain down stream of the pump input, as well as the house sewer line, which is the underground line from your structure to the municipal main or septic tank from the current 3" diameter to a 4"dia.