Wastewater FAQ's

Wastewater FAQ's

What is sanitary sewer rehabilitation and pipe renewal?
Sanitary sewer rehabilitation and pipe renewal is a program that repairs and replaces damaged sewer pipes, and, when feasible, upgrades sewer pipe to current standards.  The sewer rehabilitation process helps to fix system failures, renews systems that reached end of useful life, and reduces the occurrence of Sanitary Sewer Overflows (SSOs).

Why clean pipes?
To remove the accumulation of debris to restore pipe to full flow capacity.

What is Microbial Induced Corrosion (MIC)?
There are biological organisms (microbes) which influence corrosion. The primary concern is that this "influence" often results in an extremely accelerated rate of corrosion. It affects most alloys, such as ductile iron, steel (including stainless and galvanized), and copper, but it does not seem to affect titanium. The affect does vary between the different alloys with ductile iron corroding slower than steel.

MIC is not caused by a single microbe, but is attributed to many different microbes. These are often categorized by common characteristics such as by-products (i.e., sludge producing) or compounds they effect (i.e. sulfur oxidizing). In a general sense, they all fall into one of two groups based upon their oxygen requirements; one being aerobic (requires oxygen) such as sulfur oxidizing bacteria, and the other being anaerobic, (requires little or no oxygen), such as sulfate reducing bacteria.

General corrosion affects the entire surface or at least the wetted surface. MIC, on the other hand, is very localized. It creates a cluster and a pit beneath the cluster. There can be only a few clusters or there can be many. Within these clusters microbes rarely work alone but operate as a mixed community of differing types and groups. The different microbes perform different functions within the community. The aerobic bacteria reside in the outer layer of the cluster consuming the oxygen in the water as it penetrates the cluster. Thus, the inner portion of the nodule experiences a reduced oxygen level allowing anaerobic bacteria to thrive.

How MIC Works?

MIC operates as an individual cluster covering a pit. The development of this process occurs in three phases, which are:

  • Attachment of microbes.
  • Growth of cluster and initial pit.
  • Mature pit and cluster

In order for microbes to attach themselves to the inner wall of the pipe, the bacteria must find a desirable site. Such sites are defined as containing absorbed nutrients and having a metallurgical feature that the microbes can attach to. These features seem to be critical for MIC to occur and consist of irregularities in the pipe surface such as unlined concrete surfaces or metal pipes.

After successfully attaching to a location, a microbe produces by-products that are sticky polymers which retain organic and inorganic materials aiding in the creation of the cluster. Once the cluster is formed, it allows the underlying conditions to become chemically dissimilar to the surrounding surface. This is the start of accelerated corrosion, which initially leads to crevice corrosion. Some of the characteristics of the community at this phase are: microbes are located throughout the cluster and the pH level is lowered (acidic) within the crevice, but it is still above 4. This lower pH adds to the corrosiveness of the environment, as well as stimulating the growth of certain types of bacteria. The increased acidic level is commonly initiated by acid-producing bacteria which produce organic acids as a by-product. This acid provides a nutrient source for other bacteria whose by-product results in a buildup of hydrogen protons and an even lower pH level.

There is continued formation of the cluster over a mature pit. Such a pit not only increases in depth but also produces a tunneling characteristic. A significant condition is that the pH is less than 4. One of the factors which can contribute to the high acidic level is the weak organic acid that is produced initially. These can be converted to a stronger acid by combining with chloride from the water, thus producing hydrochloric acid. As a result of the high acidity in the pit area, live bacteria are present only in the outer portion of the nodule. At this point, the bacteria could be eliminated and the corrosion would continue as a traditional electrochemical corrosion process.

What is water recovery?
Reuse of treated sewage other than discharging to the bayou.

WWTP Outfall (Treated Effuent Being Discharged)

What is wastewater treatment (WWT)?
The goal of wastewater operations is to collect and treat wastewater, while promoting public health and welfare and protecting water resources. Sewage or domestic wastewater treatment is the process of removing contaminants from wastewater after it is collected from homes and businesses throughout the Houston area. Wastewater treatment in a plant emulates what happens in nature, but the treatment plant works faster to handle larger volumes of wastewater in a shorter time period. Treatment includes physical, chemical and biological systems that remove more than 95% of the waste before water passes through disinfection prior to discharge into the bayou. The solid waste is further processed for beneficial use.


How can I be sure that the Wastewater Treatment facility is doing its job?
Your grandparents had to worry about typhoid, cholera and other infectious diseases that are carried in raw sewage. Wastewater treatment systems serve primarily to protect the health of the general population by insuring that water sources remain clean. In today's world, people live a lot longer and in higher concentrations resulting in increased volumes of raw sewage. Modern wastewater treatment systems are critical to a safer, cleaner environment by reducing the organic load, and controlling bacteria and waterborne diseases.

The City of Houston's Wastewater Treatment Facilities are regulated by the United States Environmental Protection Agency (USEPA) and the Texas Commission for Environmental Quality (TCEQ). These agencies perform random inspection and testing of the facilities' effluent. The USEPA, through the TCEQ, issues a Texas Pollutant Discharge Elimination System (TPDES) Permit. Included in the TPDES permit are specific guidelines concerning the testing of the facilities' effluent. The City of Houston performs lab analyses as required by the TPDES permits. The effluent from the wastewater treatment plants meets specific discharge criteria that is protective of Public Health and the Environment.

Where does the water go once it is treated at a Houston Wastewater Treatment Plant?  
Reclaimed water from all of Houston wastewater plants is discharged directly into a surface waterway, usually one of the area bayous.

How many Wastewater Treatment facilities are operated by the City of Houston and where are they located?
The City operates 39 Wastewater Treatment Plants. In addition, the City of Houston also operates three Wet Weather Facilities. The wet weather facilities are operated during storm events when either the treatment plant or collection system becomes overwhelmed with additional water generated by the storm event. Plants are located in various areas throughout the City.

What occurs during a WWTP tour?
Tours at the 69th Street Wastewater Treatment Plant begin in the Administration building by briefly giving an overview based on the scaled model of the facility. Here, participants receive detailed information regarding the treatment process and theory, plant capacity, discharge permit requirements, and a brief description of the sludge processing facility. Wastewater samples are shown to aid in the discussion and to showcase the treated wastewater effluent quality by comparing it to a sample of the City’s drinking water. The tour may proceed outside for a walkthrough of the various unit processes that were discussed during the scaled model segment. Small children are bused around the plant site for this portion of the tour for their safety. Tours may be tailored accordingly to meet specific requests.

How do I request a tour of a Wastewater Treatment facility?
Plant tours can be requested and are usually conducted at the 69th Street facility, mentioned above. Tours will be scheduled based on work load and availability of plant personnel. However, every attempt will be made to accommodate citizenry request. For more information or to schedule a tour, call 832-395-5463.

Requirements for security background checks:

  • Nationals sponsored by schools, clubs, etc. require no security background check.
  • Internationals (without sponsor) require a security background check. Requesters must fill out the COH Disclosure & Consent for Release of Information (Exhibit 1) form and provide proof of United States Passport. Exhibit 1 is located at the end of FAQ’s. 


  • Tours will be scheduled based on work load and availability of plant personnel. However, every attempt will be made to accommodate citizenry request.
  • All requests must be completed 2 weeks in advance.
  • Tours typically take 1-2 hours and are conducted between 9 am and 3 pm. 
  • Chaperone required at 10:1 for less than 14 years old (drive thru), 20:1 for 14 – 18 years old (walk), and none for older than 18 years old (walk).

Don’t Need:

  • Personal protective equipment (PPE)

Who do I call if I have an odor complaint about a Wastewater Treatment facility near my home or business?




Call City of Houston Information Line at 311.


Who do I call if I have a sewer backup, overflow, or odor complaint?




Call City of Houston Information Line at 311.


What is a Wastewater Collection System?
The Wastewater Collection System is a system of pipes that transport sewage (also called sanitary sewer) from a source, such as a residence, commercial business, or industrial plant, to a wastewater treatment plant. The wastewater treatment plant properly treats the sewage for safe discharge back to the environment.

What is a Private Lateral and Private Sewer?

 Private Lateral

A private lateral is that part of the collection system that connects the resident's house to the City's wastewater main line. It is located on the resident's property and it is the responsibility of the resident to service and maintain the private lateral.

Private sewers that cross multiple properties are typically known as “community sewers.” These private sewers are shared by neighbors and must be operated and maintained by private groups that may have formal or informal agreements. Historically, the “community sewer” was constructed without following or being inspected per the plumbing code. They also tend to be built under structures and without easements or right-of-way.



What is an easement? Why I should not encroach into a Sanitary Sewer Easement?
Easements are set aside for installation and maintenance by the Wastewater Collection System. Sanitary Sewer Easement is needed for the maintenance, repair or rehabilitation of the sanitary sewers. Encroachments limit the City's ability to maintain, repair or rehabilitate sanitary sewers.

What is a sanitary sewer clean-out? Where is it located? What does it look like?
A sanitary sewer (or wastewater) cleanout is a plumbing fixture that allows access to the resident's private lateral or the City's wastewater main line.

The cleanout is typically located on the resident's property outside of the house foundation on the sanitary sewer service line. It is in line with the City's sanitary sewer main line, which can be in front or in the back of the house.


What is Inflow/Infiltration?
Inflow/Infiltration source is excess water typically from rain (surface and falling) that should not be discharged into the Wastewater Collection System.

 Inflow and Infiltration Sources

How is the cleanout cap removed?
Unscrew the cap with a pipe wrench, channel-lock pliers, or a large crescent wrench.

What if I have a backup or overflow and the cleanout is dry?
If there is a backup or overflow in the resident's home and a clean-out on the private lateral at or near the property line is dry, the stoppage must be the plumbing inside the resident's home. It is the responsibility of the resident to fix the problem.

What if I have a backup or overflow and the cleanout is holding water or overflowing?             

  • If there is a backup or overflow at the residence and a City of Houston clean-out at or near the property line is holding water or overflowing, the stoppage may be in the public portion of the sanitary sewer service or in the City's main line.
  • Call the City of Houston at 311.
  • If the stoppage is determined not to be in the City's main line, then the stoppage will be in the resident's private service lateral. It is the responsibility of the resident to make repairs to their private service lateral.

How can I prevent sanitary sewer backups or overflows?
Most sanitary sewer backups or overflows are caused by FOG (fats, oils, or grease) being put into the sink. Residents can prevent backups and overflows by disposing of FOG in the garbage and avoiding the use of the garbage disposal to put foods down the drain. Vegetables, meat scraps, butter, cooking oils, and many other foods deposit grease and solids that can build up in pipes eventually creating blockages. The fats, oils, and grease harden when they go down the drain and clog pipes in the same manner that cholesterol clogs arteries in humans. Instead of putting food waste into a garbage disposal, scrape food waste from plates and pans into the garbage. Let melted oils used for cooking solidify in a container before placing them in the garbage. For more specific information on this, visit the City of Houston's Protect Our Pipes Program at www.ProtectOurPipes.org. Sanitary sewer backups and overflows are also caused by roots or collapsed service pipes. Know where your private lateral is located and avoid planting trees and shrubs near it. Roots can creep into the sewer pipe joints and eventually cause a blockage. The best way to remove roots is to call a professional sewer cleaning service. The service pipe may need to be replaced if the pipe is cracked or collapsed.

Why are sanitary sewer backups or overflows bad?
Sanitary sewer backups and overflows are harmful to humans and the environment because of the pathogens contained in it. When sanitary sewer overflows occur, contaminants are released into the environment. Untreated wastewater is harmful to humans because these contaminants can spread disease. They are harmful for the environment because they deplete oxygen in streams that fish and aquatic wildlife need to survive.

What do I do if I see sewer overflowing from a City of Houston manhole?
Call 311.

Who do I contact for questions about my wastewater bill?
Please contact Customer Account Service at 713-371-1400 or online at https://www.houstonwaterbills.houstontx.gov/

How does the City calculate my wastewater bill?
See Customer Account Service's website at https://www.houstonwaterbills.houstontx.gov/

If I plan on digging on my property, whom do I call?
If you are going to dig on your property, please call Texas One-Call at 1-800-245-4545. Private service lines are not included in this service, City of Houston does not have these records.

How do I apply for a Sewer Tap Permit?
You can apply for a Sewer Tap Permit by contacting Customer Account Services at 713-371-1400 or online at https://www.publicworks.houstontx.gov/customer-account

Who should I contact about Industrial Discharge Permits?
For an Industrial Discharge Permit, contact Industrial Wastewater Service at 832-395-5800.

When is a grease trap required?
Commercial establishments, such as restaurants, institutional cafeterias and other public kitchens, are regulated by City ordinance. They are required to install grease traps that must be cleaned periodically. Residents don't have grease traps under the City of Houston's current Code of Ordinances. The most practical way to reduce grease from residential kitchens is to prevent grease from entering the sewer pipes in the first place.

Where can I find standard wastewater construction drawings or specifications?
Standard wastewater construction drawings and specifications can be found at

How large is the City of Houston’s Wastewater Collection System?
The City of Houston's Wastewater Collection System includes over 6,100 miles of sewer pipelines and over 380 lift stations (pump to move wastewater from lower to higher elevation).

How do I contact the City of Houston’s Wastewater Collection System Operations?
You may contact the Collection System Operations at:

4545 Groveway
Houston, TX 77087
(832) 395-4956 (Phone)

How can I send comments about this website?
For comments about this web page, please send email to SADWWOps@houstontx.gov

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Regulatory Affairs/Pretreatment & Industrial Wastewater Service

Answers to Regulatory Affairs/Pretreatment & Industrial Wastewater FAQ's:
Do we need a permit?

Industrial facilities and certain commercial facilities, which plan to discharge industrial waste to the City's sanitary sewer system may be required to obtain an Industrial Waste Permit. For our purposes, Industrial Waste is defined as:

"Any waterborne solid, liquid or gaseous waste, resulting from any production, industrial, manufacturing or food processing operation or from the development, recovery or processing of any natural resource, including waste that is required to be pretreated by Chapter 47, Section V or the City's Plumbing Code."

Industrial waste also includes wastes subject to specific categorical pretreatment standards at 40 CFR Parts 405-471 or regulated by 40 CFR Part 403.

You do not need an Industrial Waste Permit if:

Your business is a self-service or commercial (not industrial) laundry.

Your business is a restaurant.

Your business is a car wash.

Additionally, the City of Houston is not currently requiring an Industrial Waste Permit for the following operations: hospitals, analytical and research laboratories, small photographic developing operations and printers.

However, any facility discharging industrial waste to the sanitary sewer system may be required to obtain an Industrial Waste Permit if the Industrial Wastewater Service makes that determination.

Steps to Obtaining a Permit

The first step in obtaining an Industrial Waste Permit is to contact the Industrial Wastewater Service at (832) 395-5800 to discuss your firm's operations and request an inspection of your facility.

Once the City performs an inspection, and it has been determined your firm will require an Industrial Waste Permit, the City will send written notification that will include a permit application. The Industrial Wastewater Service also offers a Pre-Application meeting to discuss the steps involved with obtaining a permit and assist new facilities with the requirements. 

After submitting your permit application to the City, the Industrial Wastewater Service will review it and, if the application is acceptable, an Industrial Waste Permit will be issued. All facilities required to obtain an Industrial Waste Permit must pay a Permit Application Fee and a Permit Administrative Fee as established in the City's fee schedule. Industrial Waste Permits are issued for two (2) years and are renewable after that period of time. The Application and Administrative Fees are subject to change each year. Each permitted industry will receive a permit renewal notification from the Industrial Wastewater Service at least one month before their permit expires and that notification will state the current permit renewal fees.

What is a Significant Industrial User (SIU)?

The term Significant Industrial User (SIU) applies to an industry that discharges to the sanitary sewer system if that industry meets the following criteria:

1. The industry is subject to federal regulations at 40 CFR Parts 405-471.
2. Any other industrial user that discharges an average of 25,000 gallons per day or more of process wastewater to the POTW (excluding sanitary, non-contact cooling and boiler blow down wastewater); contributes a process waste stream, which makes up 5 percent or more of the average dry weather hydraulic or organic capacity of the POTW treatment plant; or is designated as such by the control authority as defined in 40 CFR 403.12 (a) on the basis that the industrial user has a reasonable potential for adversely affecting the POTW operation or for violating any pretreatment standard or requirement.

SIUs are further classified as Categorical Industrial Users (CIU) if they are subject to federal discharge limitations developed by the EPA. CIUs are also subject to the City's local limits. All other SIUs are classified as Non-Categorical SIUs and are subject only to the City's local sanitary sewer discharge limits.

What are the Local Discharge Limits?

Houston enforces local limits, as mandated by the EPA and the Clean Water Act. The City also enforces guidelines set forth in City of Houston Ordinance Section V., City Code Sections 47-186 through 47-208, which gave the City enforcement authority over permit violations. Section 47-194 (Standard of Quality) establishes the discharge limits as listed below.

Grab Limit (mg/L)
Composite Limit (mg/L)
Cyanide (Amenable)
Oil and Grease

Other Prohibited Discharges

  • Acids with a pH value lower than 5.0 or alkalis with a pH higher than 11.0.
  • Sulfides in concentrations greater than five (5.0) milligrams per liter.
  • Any liquid or vapor with a temperature exceeding 45 degrees Celsius (113 degrees Fahrenheit).
  • Waste streams with a closed cup flash point of less than 140 degrees Fahrenheit or 60 degrees Celsius.
  • Any flammable or explosive liquid, solid or gas.
  • Any discharge that forms a discernable floating layer of oil and grease on the surface of the discharged water.
  • Solid or viscous substances capable of obstructing flow in sewers.
  • Any noxious substance that can form an objectionable or hazardous gas.
  • Petroleum oil, non-biodegradable cutting oil or products of mineral origin in amounts that cause interference with or passes through the sanitary sewer system.
  • Pollutants resulting in toxic vapors, gases or fumes that may cause acute utility worker health and safety problems.
  • Any trucked or hauled waste except where the utility official has permitted a designated discharge point.
  • Unusual concentrations of BOD, suspended solids or total dissolved solids such as sodium chloride or sodium sulfate.

What are the Prohibited Wastes?

There are certain prohibited wastes that may not be discharged under any circumstances, regardless of your pretreatment classification. They are:

  • Flammable, reactive, explosive, corrosive or radioactive substances.
  • Noxious or malodorous materials.
  • Medical or infectious wastes.
  • Solid or viscous materials, which could cause obstruction to the flow or operation of the treatment plants.
  • Toxic substances.
  • Non-biodegradable oils
  • Pollutants, which result in the emission of hazardous gases.

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What is a Sanitary Sewer Surcharge on High Strength Waste?

A sanitary sewer surcharge billing rate is imposed on an industrial user for discharges containing concentrations of Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS) exceeding values found in domestic discharge. The City will use a predetermined formula to calculate a sanitary sewer surcharge for wastewater billing. The Industrial Wastewater Service will perform an annual evaluation to determine what each permitted industry's sanitary sewer billing rate should be. The average concentrations for BOD and TSS from both City and industry self-monitoring are used to arrive at a sewer-billing rate. The increased sewer rates pay for the cost of the additional treatment at the City's wastewater treatment plant. Treatment and removal of "high-strength" waste requires extra operating expenses, such as the cost of additional chemicals, power, solid storage capacity and final disposal.

What are the Pretreatment Guidelines, and how are they enforced?

Industrial facilities, which do not comply with permit requirements are subject to enforcement action. Houston utilizes a progressive enforcement response plan with actions ranging from issuance of Notices of Violation (NOVs) and Administrative Orders to sewer or water service termination and administrative fines. The key to responding to a violation notice is communication with the Industrial Wastewater Service.

What are the Federally Regulated Industrial Categories?

The following is a list of the industrial categories at 40 CFR Parts 405-471 that establish effluent limits for industries that discharge industrial waste to the sanitary sewer system. If an industry performs a specific operation that is listed in one of the following categorical regulations, that industry is identified as a categorical industry. New categorical regulations are currently being developed by the EPA, and this list should not be used to determine if these are the only categorical regulations that have been promulgated.

  • Aluminum Forming (40 CFR 467)
  • Asbestos Manufacturing (40 CFR 427)
  • Battery Manufacturing (40 CFR 461)
  • Centralized Waste Treatment (40 CFR Part 437)
  • Coil Coating, Phase I (40 CFR 465)
  • Coil Coating, Phase II - Can Making Subcategory (40 CFR 465)
  • Copper Forming (40 CFR 468)
  • Electrical and Electronic Components, Phase I and Phase II (40 CFR 469)
  • Electroplating (40 CFR 413)
  • Fertilizer Manufacturing (40 CFR 418)
  • Glass Manufacturing (40 CFR 426)
  • Ink Formulating (40 CFR 447)
  • Iron and Steel (40 CFR 420)
  • Leather Tanning and Finishing (40 CFR 425)
  • Metal Finishing (40 CFR 433)
  • Metal Molding and Casting (40 CFR 464)
  • Nonferrous Metals Forming and Metal Powders (40 CFR 471)
  • Nonferrous Metals Manufacturing, Phase I and II (40 CFR 421)
  • Organic Chemicals, Plastics and Synthetic Fibers (40 CFR 414)
  • Paint Formulating (40 CFR 446)
  • Pesticide Chemical Manufacturing (40 CFR 455)
  • Petroleum Refining (40 CFR 419)
  • Pharmaceutical Manufacturing (40 CFR 439)
  • Porcelain Enameling (40 CFR 466)
  • Pulp, Paper and Paperboard and the Builder's Paper and Board Mills (40 CFR 430 and 431)
  • Rubber Manufacturing (40 CFR 428)
  • Soap and Detergent Manufacturing (40 CFR 417)
  • Steam Electric Power Generation (40 CFR 423)
  • Textile Mills (40 CFR 410)
  • Timber Products (40 CFR 429)
  • Transportation and Equipment Cleaning (40 CFR 442)

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Exhibit 1