What happens to your water after it goes down the drain

When water leaves a sink, shower, toilet, or washing machine, its journey is just beginning. Used water, known as wastewater, travels through a network of private plumbing and public sewer mains before it reaches a treatment facility. The system is designed to protect public health, local waterways, and the community’s long-term infrastructure.

In Susanville, responsible wastewater management depends on both utility operations and everyday household choices. Fats, wipes, chemicals, medicines, and other unsuitable materials can damage pipes, interfere with treatment, or create hazards for workers. Residents can find municipal utility information, public works updates, and service resources through the City of Susanville Public Works Department.

The path is generally hidden from view, but it involves several carefully controlled steps. Each stage removes a different type of material, from large debris to dissolved pollutants and disease-causing organisms.

From household plumbing to the sewer main

Water first passes through a building’s drainpipes. Gravity usually carries it from fixtures into a private lateral, the pipe connecting a property to the public sewer system. The wastewater then enters larger sewer mains beneath streets, where gravity flow and, in some locations, lift stations move it toward treatment facilities.

The material in this flow is called sanitary sewage. It contains water mixed with human waste, food particles, soap, grease, cleaning products, and other substances washed down drains. Rainwater should generally follow a separate path. When stormwater enters sanitary sewers through damaged pipes or improper connections, it can overload the system during wet weather.

Sewer pipes, manholes, pumps, and treatment equipment require regular inspection and maintenance. Crews may use cameras, cleaning equipment, leak detection, and repair projects to keep wastewater moving safely and prevent overflows.

The first steps inside a treatment facility

At the treatment plant, incoming wastewater passes through screens that catch large objects such as rags, plastic items, wipes, and other debris. Even products marketed as flushable may fail to break down quickly and can cause blockages or equipment problems. The captured material is removed and handled as solid waste.

Next, grit removal separates dense particles such as sand, gravel, eggshell fragments, and small stones. These materials can wear down pumps and mechanical equipment if they remain in the wastewater stream. Removing them early helps protect the rest of the treatment process.

The wastewater then enters settling tanks. During this primary treatment stage, heavier organic solids sink to the bottom as sludge, while grease and lighter materials rise to the surface for removal. The clarified liquid continues to biological treatment.

How microorganisms clean the water

Biological treatment uses naturally occurring microorganisms to consume dissolved and suspended organic matter. Air may be added to treatment tanks so beneficial bacteria can thrive and break down pollutants that cannot be removed by screening or settling alone.

After biological treatment, another settling stage separates the microorganisms and remaining solids from the cleaner water. Some of the settled biological material may be returned to the treatment process, while excess solids are removed for additional handling.

Treatment standards determine how clean the discharged water must be and how the facility is operated. Testing can measure factors such as suspended solids, oxygen demand, nutrients, and bacteria. These controls help ensure that treated effluent meets applicable permits and environmental requirements.

Treatment stage	Main purpose	Materials removed
Screening	Protect equipment and prevent blockages	Wipes, rags, plastics, and large debris
Grit removal	Reduce wear on pumps and tanks	Sand, gravel, and dense particles
Primary settling	Separate materials by weight	Sludge, grease, and floating solids
Biological treatment	Break down dissolved organic matter	Organic pollutants and suspended matter
Final clarification and disinfection	Produce safer treated effluent	Remaining solids and harmful organisms

What happens to sludge and other solids

Wastewater treatment does not make pollutants disappear. It separates them from the water stream and concentrates many of them in sludge, screenings, grit, and grease. These materials must be collected, processed, transported, and disposed of according to health and environmental rules.

Solids may undergo stabilization, thickening, dewatering, or other treatment steps. The exact methods depend on the facility’s equipment, permits, operating conditions, and available disposal options. Proper handling reduces odors, pathogens, and the risk of contamination.

Household chemicals can complicate this work. Paint, solvents, pesticides, automotive fluids, and similar products should never be poured into sinks or toilets. Residents can review guidance on household hazardous waste to identify safer disposal options.

Where treated water goes next

After treatment, the resulting effluent may be discharged under a regulatory permit to an approved receiving water or managed through another authorized method. The receiving environment and permit conditions determine the required level of treatment, monitoring, and reporting.

Treated wastewater is not the same as drinking water. Even when it meets discharge requirements, it is managed for its permitted use and should not be treated as a household water source. Protecting rivers, groundwater, and soil depends on keeping untreated sewage and harmful materials out of the system in the first place.

Water conservation also supports wastewater operations. Using less water reduces the volume that must be pumped and treated, while fixing leaks can prevent unnecessary flows through private plumbing and public sewer infrastructure.

Stormwater follows a different route

Water from rain, snowmelt, streets, parking areas, and outdoor surfaces is stormwater. It can collect oil, sediment, litter, fertilizer, pet waste, and other pollutants as it moves across the ground. Unlike sanitary wastewater, stormwater may receive limited or no treatment before entering drainage channels or natural waterways.

That difference makes outdoor behavior important. Washing vehicles where soapy water flows into a storm drain, allowing soil to wash off a property, or leaving trash near a gutter can affect local water quality. Keeping leaves, sediment, and debris away from inlets helps maintain drainage capacity and reduce blockages.

Sanitary sewer and storm drainage systems can also be affected by inflow and infiltration. Cracked pipes, loose connections, and illegal cross-connections allow groundwater or rainwater to enter the sewer network, increasing treatment costs and reducing available capacity.

Simple habits that protect the system

• Flush human waste and toilet paper only; place wipes, paper towels, and hygiene products in the trash.
• Collect cooking grease and liquid fats in a container, let them cool, and dispose of them with household waste as appropriate.
• Keep paint, fuel, pesticides, solvents, medicines, and other chemicals out of drains.
• Use a drain screen to catch hair and food particles before they enter household plumbing.
• Report sewer odors, backups, overflowing manholes, or suspected leaks promptly through the appropriate city service channel.

Learning what belongs in a drain protects private plumbing, public sewer mains, treatment equipment, and the environment. Before disposing of an unusual material or reporting a wastewater concern, check the City of Susanville Public Works website for current contacts, service information, and local guidance. Small decisions at the household drain help keep the entire water cycle safer and more reliable.