Types of Septic Pumps and Sump Pumps

Types of Septic Pumps and Sump Pumps
Readers have asked the difference between a sump pump, a septic efflent pump, and a sewage or grinder pump. The distinction is important when installing or repairing a septic system that uses pumps since choosing the wrong pump can mean a short operating life or unnecessary expense. In addition to explaining these different septic pump types, we describe a community sewage pumping station.
Beware, there may be some confusion, depending on with whom you speak, because people don't always use just the right terms for construction or septic system parts - and the right sewage pump term, or right septic handling product versus the wrong one can be an important distinction.
What is a Sump Pump?
The photo on the left is what you're likely to see if your basement has a modern sump pump. A pump with a float switch intended to turn the pump on when ground water rises in the sump pit (or flows stupidly across your basement and into the pit) where it is discharged to a storm drain or the property surface. The photo on the right shows a duplexed sump pump system - this was a really wet basement. Sump pumps are normally used to pump clear liquid, such as ground water from a wet basement sump pit or gray water from a basement laundry sink. These pumps are light-duty and have no ability to pass solid debris other than perhaps fine soil or silt that may be in groundwater.
Some manufacturers may also call sump pumps de-watering pumps.
 
What is a Sewage Ejector Pump or Pre-Packaged Grinder Pump
Sewage ejector pumps, or grinder pumps, are designed to pump sewage or blackwater to a destination such as an elevated septic tank or to a city sewer (for homes whose lower baths are at a depth below the level of their sewer line). A grinder pump, (there is more than one grinding method) reduces sewage to a finely ground slurry of waste and water which can then be pumped or forced to its destination. If your building's drain system is at a level below the municipal sewer line, or if your septic drainfield or tank and fields are uphill from the building, you need a grinder pump and a forced-main sewer system.
In their most common usage, packaged systems are sold in a plastic "can" which contains the grinder pump, a float control to turn the pump on and off, and watertight fittings that permit connection of the system to the building electrical system (to supply power to the pump) and to the building drain waste vent system. The pump manufacturer will provide a table of pumping capacity needed to overcome specific head or lift requirements and length or pipe run from the pumping station to its destination.
The general name for these pumps is sewage grinder pumps if they are intended to grind and move black water or sewage, or sewage effluent pumps if the pump is intended only to move clarified effluent, say from a septic tank to a drain field. Some of the common pump brands include ABS pumps, Crane (centrifugal grinders) pumps, Environment One or E/One pumps, Goulds, Hydromatic pumps, Liberty pumps, Little Giant, Myers pumps, Tsurumi, Webtrol, and Zoeller sewage grinder pumps. Several sewage pump manufacturers produce a separate line of commercial or municipal sewage grinder pumps from those used in residential application.
 
What is a Free-Standing Sewage Grinder Pump
A grinder pump is about the same as the packaged on in-can sewage ejector pump discussed above, except that the grinder pump is a heavy-duty pump which, instead of being in a prepackaged container such as for use to install a single basement bathroom at a level below the building sewer outlet height, the grinder pump is installed right in a septic tank. The grinder macerates sewage so that it can be pumped through a (usually smaller-diameter, perhaps 2") force main to an uphill septic tank or sewage pumping station or to a municipal sewer line, all of which are in this case located higher than the pumping location. Thus the need for the pump.
The "pump in a can" or packaged septic grinder pump systems pictured above on this page have limited lift capacity. Where a lot of vertical lift is needed, a submersible sewage grinder or effluent pump will be used and will be installed at or near the bottom of the holding tank.
If someone installs an ordinary dewatering sump pump to pump sewage they're opting for an inexpensive pump that is not going to last long at all because it's being mis-used and it's going to clog up. Using an ordinary dewatering sump pump to move septic effluent is making a similar, if not as completely egregious mistake.
If you are pumping clarified effluent out of a septic pumping chamber which itself is downstream from and separated from a septic tank which contains solids and floating scum, then your pump does not need to be a grinder pump. However even in this case I would avoid the common $50.00 (ballpark) common sump pump because it's unlikely that the pump will have the duty cycle and durability to give you a long term, reliable septic system operation.
The best design for any pumping system, solids to a tank or effluent to an elevated drainfield, is a duplex pump system so that you have a chance to keep a working house drain system even when a pump fails.
Duplex Septic Pump System Designs
There are two common pump-pair setups:
1. two pumps alternate, taking turns running - I prefer this method as you are spreading the wear over two pumps and you'll know when one fails and have a chance to repair it.
2. one pump normally runs and the second kicks in only if the effluent level rises above a failsafe point. This handles either unusual flows into the system (uncommon) or the case where the 1st pump is broken. I don't like this setup as much as we're never testing pump #2 until the very day it's absolutely needed.
Pump controls are produced by several manufacturers including Anchor Scientific, Aquawarx (control panels), B/W Controls, Orenco, Rhombus, SJ Electro, and CSI.
(There are so many septic tank and holding tank and pumping chamber tank companies that I've not tried to list them.
Septic Pump Alarm Systems
Any sewage pump setup should include an alarm that tells you when a pump has stopped working. In a duplex system the alarm indicates that you're running on the backup pump. In a single-pump system the alarm means you have very little septic capacity before repairs are made, since there is no working pump.
 
 
What are Community & Housing Development Septic Pumping Stations?
A community sewage pumping station uses a large centralized chamber to receive wastewater from multiple buildings at a single site or development and then grind and pump the wastewater onwards towards a wastewater treatment facility.

Sewage pumping stations are needed where all or some of the homes or buildings in a community are located downhill from the greater community's sewage mains. Wastewater drains by gravity (or if necessary by individual building septic pumps) from individual buildings in the community to the local septic pumping station which has a holding tank big enough to act as a receiver for wastewater from the community.

From the receiving station, wastewater passes through one or more sewage grinder pumps through a pressurized sewage force main (pipe) which transports the waste uphill to a location from which the wastewater can drain by gravity through additional piping to the community's wastewater treatment facility.

The pumping station will typically use two or more sewage grinder pumps to move wastewater uphill to the larger community's sewage mains where it passes to the sewage treatment plant. Multiplexing pumps helps assure that the community's waste will be handled even if one pump fails, and also permits staging of pump operations to bring more pumps online if the inflow rate increases.

 
We have some special concerns for community sewage pumping stations or "septic pumping stations" or "force mains" as they may be called in some areas.
  • Child safety The pumping station shown here has an access cover that was not locked - leaving us worried that a neighborhood kid might explore and fall into this deep pit - a nearly certain and quick fatality.
  • Sewage Pumping Station Reliability and Sewage Bacukps If the system is not maintained or lacks an adequate number of pumps and backup power, the entire community can be without wastewater services. For example, during an unusually heavy rainfall, or during a local power outage, the community served by the pumping station shown in this photograph lost the service of its pumping station.
One unpleasant effect was that homes nearest to the pumping station's receiving chamber suddenly had everyone's sewage backing up into their homes. In addition to omission of a backup generator for the system, the plumbing contractor had not installed check valves in the sewage lines at each home.  Is it a blocked drain or the septic system? - A First Step for Homeowners. The contaminants in sewage that may be left behind when sewage backs up in a building are identifying water and soil contaminants produced by onsite waste disposal systems.


Information taken from articles written by:

Michael P. Vogel, Ed.D., MSU Extension Service Housing Specialist

National Small Flows Clearinghouse

North Carolina Extension Service