Sewage stinks. It’s not a very pleasant thing to think about and most people probably would prefer their sewage to be out of sight and out of mind. Few things are as big a headache for a property owner or municipality manager as backed-up sewage water. Whether the building in question is a home or business, the smell of sewage can produce a dreadful environment. Removing wastewater and sizing a new pump for your sewage pump system is an involved process.
If you are experiencing a problem such as the sewage water backing up or simply not draining quickly enough, it is important to determine the origin of the problem and think about possible solutions. If a pump stops working because of age or natural wear, it is easy enough to replace the old model with a new one. But you should take the opportunity to examine the holistic health of your sewage system.
PumpProducts.com technicians installing a sewage pump system.Similarly, if you are building a new house or you just refurbished your basement and want to add a bathroom, it is imperative to consider all the aspects of wastewater removal in your system. If the system is a new project, you may need to dig a new sewage pit to have a basin installed.
Examining the whole of a system can help you update your infrastructure to comply with new codes, identify potential problem points before they occur, or simply make your fluid transportation more efficient, saving time and money in the long run.
This blog post will walk you through the process of sizing a sewage pump for a system. First, it is essential to understand the basics of municipal sewage systems and whether or not you actually need a sewage pump.
Understanding How Sewage Systems Work
Most American municipal systems have two types of underground sewer lines dedicated to water collection and disposal: the storm sewer and the sanitary sewer.
The storm sewer collects rainwater surface runoff from catch basins and transports the water to the nearest natural reservoir, such as a river or stream. The sanitary sewer transports wastewater directly from building sewage systems to a water treatment plant where contaminants are removed (Some older cities have combined sewer systems).
For buildings at grade (ground level), gravity takes care of transporting the wastewater to the sanitary sewer. Sewage pumps are necessary if the sanitary sewer line is located at a level above your home wastewater line or if you have a toilet below the sanitary sewer line, as is often the case for basement bathrooms.
As the name suggests, sewage lifting stations also rely on sewage pumps. Lifting stations are integral links in the chain connecting neighborhoods to water treatment facilities.
Check the codes for your area to see what aspects you are responsible for within the system. Your municipality should also have exact records of where your property line ends and public property begins. To determine if a problem is with the property sewer line or the public line, try contacting the town or utility company. A plumbing professional can also assist with diagnosis.
The sewage system can be configured in various ways. Automatic systems will require float switches and a control panel to turn the pump on or off.
A simplex system is a one pump system while a duplex system is a two pump system in which each pump serves as a redundancy to share the workload, resulting in less wear on the pumps. Simplex systems are mostly used in domestic settings. Duplex systems are recommended for municipal, commercial and industrial applications.
Selecting a Model
When selecting a pump model you should know the voltage, phase of power, amperage and horsepower of your previous pump. This information should be listed on a pump tag. The video below provides a guide to using the tag to identify your pump. If you cannot locate the tag or if the label is degraded, you can try taking a picture of the pump and sending it to the experts here at Pump Products.
The pump’s discharge size is important for configuring the pump with the existing pipe system; the discharge pipe size should never be a smaller diameter than the pump’s discharge outlet. Suction/discharge sizes will sometimes be listed on the casing.
The average size for waste solids in residential systems is 1 ½" or larger. For commercial or industrial systems, the average solids size is 2 ½” or larger.
Flow and total dynamic head (TDH) are integral in selecting a pump. Your water flow requirements, measured in GPM, are based on the number of people using the system, peak usage times and the number of water fixtures (e.g. toilet, sink). The charts for discerning water supply fixture units for both individual and group fixtures, as well as a chart for converting the WSFU demand to GPM can be found here.
The GPM is also critical information that you need to calculate your TDH. Scouring the pipes is important to prevent clogs, water hammer and backflow. Once you have the flow and head you can select a pump using a manufacturer's pump performance curve charts.
Selecting a Basin
The sewage basin or holding tank serves as a temporary receptacle for the wastewater while also housing the submersible sewage pump that ejects the wastewater to the main sewer line. Correct sizing of the basin is critical for smooth discharge, preventing overflow and ensuring safe pump cycling.
To size your basin, here’s what you should keep in mind:
-- Whether you are using a simplex or duplex system.
-- Required construction material of the basin body and of the lid (poly, fiberglass, steel).
-- Pipe fits: The basin has a discharge and suction pipe that should size match with both the sewer line pipe and the pump’s discharge pipe.
-- The basin lid should have a vent to prevent air locking and aid in the management of gases.
-- Required size for the basin inlet.
-- Guide Rails: It is strongly recommended to install a basin on a guide rail system. The guide rail makes removing the pump easy, reducing maintenance time and cost while keeping personnel safe.
The actual basin capacity is important to make sure the pump cycles properly. For instance, if the basin is too small for your flow requirements, the pump will keep running to evacuate the water and prevent overflow.
A minimum diameter of 24” is required for simplex systems while duplex systems require at least 36”. Here’s a handy chart from Goulds that explains how to use your GPM and gallons per inch to size your basin.
Other Accessories and System Components
If you are installing a new control panel, make sure you know the proper electrical supply requirements for the pump and building in question. Most homes and standard commercial buildings in the United States typically operate at a single phase power and 115/230 V. In the U.S., electrical grids operate with a frequency of 60 Hz. Amp range is also an important factor.
Pump Products experts recommend using a wide angle/tethered style float switch as other switches might be more susceptible to clogging from waste solids. If you have correctly sized your basin, make sure the float switch cord is the proper length to operate within that basin. The amperage range of the float should be compatible with the pump.
A check valve is required to prevent backflow and for code compliance.
Sewage or Grinder (or Shredder?) What’s the Difference?
When considering terminology, remember that all grinder pumps are sewage pumps but not all sewage pumps are grinder pumps. Sewage pumps are designed to pass waste solids up to 2” in diameter. Grinder pumps can turn waste solids into a slurry that can be more easily transported through the piping. In this case, “waste solids” refers to organic waste and standard issue toilet paper that can be easily broken down.
A common misconception is that grinder pumps can macerate heavy objects such as feminine products, plastics and loose items of clothing. If clogging is a consistent problem - say you own a motel and guests are inconsiderate about what they flush down the toilet - it may behoove you to select a dedicated nonclog shredder or cutter pump. As seen in this video, shredders are expressly designed to destroy synthetic solids, such as diapers or plastic bottles.
Sizing and configuring a sewage system is delicate, comprehensive process. Other important factors to keep in mind are the temperature of the liquid that will be pumped, as well as the construction materials of the pump itself. Durable materials and a strong warranty are recommended. Know if the materials are rated for indoor or outdoor applications. Outdoor components require weatherproofing.
If you do not want to deal with the inconvenience and expense of buying separate components consider buying a sewage system package. Packages can include all the pre-assembled components, streamlining the process considerably.
