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Wastewater from the Texas State University San Marcos campus and STAR Park flows into the sanitary sewer system and is treated by the City of San Marcos Wastewater Treatment Plant (WWTP). The treated water is then returned to the San Marcos River. Although the wastewater does receive treatment, we still need to be conscientious about what items are put down the indoor drains. Excessive pollutants in our wastewater can not only interfere with the treatment process, causing pollutants to enter the river, but it can also cause the university to violate our permit with the city. It is important to know what can and cannot go down the drain. 

Bathroom with two sinks and stalls

Campus Bathrooms

When you flush the toilet or turn on the sink in the bathroom, all that water gets directed to the sanitary sewer system.

What is Wastewater?

Wastewater, also called sewage, is any water that has been used for domestic, commercial, or industrial purposes, and contains waste produced from those processes. 

Wastewater generated inside campus buildings flows into a sanitary sewer via drains from bathrooms, laboratories, studios, laundry facilities, kitchens and dining halls, and mechanical rooms or utility plants. 

Prohibited Drain Disposal 

Federal, state, and local regulations prohibit chemicals and other hazardous materials from entering the drain. These items include:

  • Flammable, toxic, corrosive, or reactive chemicals and chemical solutions. Examples are chemicals and solvents used or generated in campus labs, solutions with heavy metals, solutions with a pH less than 6 or greater than 11, and strong cleaning agents.  
  • Solid or viscous materials such as rags, wax or paraffin, plastics, ashes, sand, feathers, glue, silicone, or caulk. These items can cause clogged pipes, sewage backups, and make wastewater difficult to treat.
  • Fats, oils, and grease (FOG).  Never pour old cooking oil or motor oil down a drain. FOG can clog pipes and cause sanitary sewer backups. 
    • For help disposing of used oils generated through work, research, or academic classes contact EHSREM
    • For help and tips on disposal of fats, oils, and grease generated as part of living on campus, please see the Dorm Drain Tips below. 
  • Pharmaceuticals and over the counter medications
    • Pharmaceutical and over-the counter medications should never be flushed down the toilet or drain. 

All chemical wastes are collected through the Hazardous Waste program for proper disposal by EHSREM. Waste disposal services for hazardous and non-hazardous chemical wastes generated on campus as a result of work, research, or academics are provided free of charge by EHSREM. 

Drain Tips for Working and Learning on Campus

  • Storage

    Keep areas in and around sinks clean. Don’t store chemicals adjacent to or above lab sinks, and certainly not IN sinks. 

    Do not leave contaminated glassware in the sink when you leave your laboratory.


    Most chemicals and chemical solutions generated in laboratories will be picked up by EHSREM for proper disposal through the EHSREM Hazardous Waste Program. This service is free of charge to all waste generators on campus. Examples of chemicals and chemical wastes which are widely generated in labs on campus and are prohibited from drain disposal include, but are not limited to:

    • Ethanol, acetone, methanol, isopropyl alcohol (IPA), trichloroethylene, dichloromethane
    • Specimen preservatives such as Formalin, Carosafe, and Wardsafe 
    • Aqueous solutions with metals such as aluminum, arsenic, cadmium, copper, chromium, lead, mercury, molybdenum, nickel, selenium, silver, or zinc.
    • Ethidium Bromide Gels and Solutions
    • Dyes and Stains such as Coomasie Blue, Bradford Reagent, Crystal Violet, and Safranin
    • Corrosive solutions used for glassware cleaning, such as base baths or Chromerge. EHSREM strongly recommends laboratories use alternative glass cleaning products such as Alconox, NoChromix, or simple soap and water. 

    Are any non-hazardous solutions ok to be drain disposed?

    In small volumes (no more than 500 mL per lab per day), certain non-hazardous solutions are permitted for drain disposal. The solutions permitted for drain disposal (shown below) must have a pH greater than 6 and less than 11 and must not contain metals.

    • Physiological saline and non-toxic salts, such as sodium chloride, magnesium chloride, calcium chloride, or potassium chloride, in dilute form
    • Inorganic buffers (phosphate or bicarbonate based)
    • Sugar solutions
    • Growth media solutions which have been rendered non-infectious

    If you have a solution you believe can be drain disposed that is not on the list above, please contact EHSREM. EHSREM may provide drain disposal authorization on a case-by-case basis. Do not assume that a solution can be drain disposed even if it was ok in a previous work location. Local restrictions are different everywhere.  

  • Art studios produce an array of chemical and non-chemical wastes that cannot be disposed of down the drain. These wastes are collected and disposed of through the EHSREM Hazardous Waste Program. Follow the tips below to help keep excessive pollutants out of our wastewater.

    • Latex, acrylic and other non-oil-based paint rinsewater and ink rinswewater may not meet the technical definition of hazardous wastes, however, they are considered high-strength wastewater. Therefore, these wastes should not be poured down the drain. In addition, latex paint can clog pipes and cause sewage backups.
    • Certain types of paints used in art studios may contain low levels of hazardous heavy metals, such as cadmium.  Avoid using paints and pigments containing heavy metals, such as cadmium, cobalt, and chromium.
    • Always follow the brush and equipment rinsing instructions posted in your studio. 
    • Some art studios, such as jewelry-making and photography, use chemical solutions in their processes. All chemical waste must be collected in a waste container and disposed of through the EHSREM Hazardous Waste Program.
  • Utility Pipe Cleaning and Maintenance Discharges

    Occasionally, it may be necessary to discharge non-routine wastewater to the sanitary sewer for maintenance or new construction activities. Utility piping projects use cleaning agents and the wastewater generated from them may be corrosive or contain toxic metals. Per TXST specifications, cleaning agents may not be nitrate/nitrite based. Contact EHSREM at 512-245-3616 at least 14 days ahead of the activity to discuss requirements for discharge, which may include sampling and city authorization prior to allowing the discharge. 

    Construction Wastewater

    Wastewater generated by construction contractors, such as paint rinsewater or equipment rinseate, may not be drain disposed. Paint brushes and other equipment cannot be washed onto the ground or vegetation. This waste must be collected by the contractor and taken back to their work location for proper disposal. 

    Super chlorinated water from domestic pipe cleaning may not be discharged to the ground or the sanitary sewer. This water must be dechlorinated to less than 1 part per million and tested prior to disposal in the sanitary sewer. EHSREM must be notified of all such discharges along with the estimated volume at least 14 days in advance.

    Swimming Pool Discharges

    Swimming pools must be dechlorinated to less than 1 part per million and the discharge must be monitored to ensure there is no hydraulic loading to the sanitary sewer. The department responsible for the discharge must notify EHSREM at least 14 days in advance of the planned discharge and provide the estimated volume and discuss other potential requirements.   

    Spills or Non-Compliant Discharges

    For chemical spills or discharges to the sanitary sewer which contain toxic or corrosive substances (also called Slug Discharges), contact EHSREM at 512-245-3616 immediately. To learn more about Slug Discharges, please review the Texas State Slug Control Plan.

Drain Tips for Campus Residents

  • Cooking food generates fats, oils, and grease (FOG). FOG poured down kitchen drains accumulates inside sewer pipes. As the FOG builds up, it restricts the flow in the pipe and can cause untreated wastewater to back up into homes and businesses, or causing manholes to overflow into parks, streets, and storm drains, polluting our creeks and river. 

    You can help prevent FOG problems by taking the following steps when you use your dorm kitchens:

    • Scrape all food from dishes, even salsa, marinades, salad dressing, and sour cream, into the trash. If your worried about making a mess in the trash, simply pour liquid food wastes into a sealable plastic bag, soda bottle, or jar before placing it in the trash.
    • Collect cooking oil and grease from pots and pans in a jar and dispose in the trash. 
    • Wipe residual oils and grease from pots and pans before washing the dish. Never use hot water and soap to wash FOG down the drain. FOG will solidify again once it cools down the line. 


  • With numerous dorms on campus and thousands of students living on campus, dorm laundry rooms are constantly in use, contributing large loads of wastewater to the sanitary sewer system. To minimize your impact: 

    • TXST dorms are equipped with high efficiency washers to help conserve water, so make sure you use high efficiency detergent (look for markings on the label).
    • Only use the amount that is called for. More is not better.  
    • Liquid laundry softeners add unnecessary chemicals to wastewater. Use dryer sheets instead.
    • Reduce your laundry loads – is that shirt really dirty if you only wore it for a few minutes?
  • We use many products in the bathroom, from soap and shampoo to toilet paper, wipes, and feminine products. All of the products we choose and the way we use them have an impact on wastewater. Minimize your impact by following these tips:

    • Choose products which are eco-friendly and don’t contain harsh chemicals.
    • Use products in a manner and volume only as directed on the product label. More is not always better.
    • Never flush wipes down the toilet, even the flushable ones.  Same goes for feminine products. These products do not biodegrade easily and often wrap around sewer pumps, damaging equipment or clogging pipes.
    • Never flush unused pharmaceuticals or over the counter medicines down the drain. These products generally pass through a wastewater treatment plant without breaking down, resulting in pollution. Unused pharmaceuticals and medications can be disposed properly at secure and anonymous drop boxes. To find a secure drop box near you, visit the Rx Drug Drop Box website.  
  • When hosting an event on the TXST campus, all wastewater produced form handwashing, cooking, dishware washing, paint rinsewater, or any other activity must be properly disposed of. Visit the TXST Event Permitting and Safety Page to learn more.