Septic systems and connection to central sewer have the same goal: treat your wastewater. But, they function differently, and knowing your system is important.

With central sewer, waste is pumped through underground pipes to a sewage treatment plant, such as the Big Sky Water & Sewer District’s Wastewater Treatment Facility.

Septic systems treat waste on-site in a septic tank. The treated water then flows to a drainfield where it is filtered through the soil and into the groundwater. In our community, groundwater eventually becomes our drinking water, or flows into the Gallatin River.

Public water and sewer districts have the ability to filter and treat waste at a higher level and rate than septic systems, but there are still ways to make sure that your septic system is functioning properly and having minimal impact on the Gallatin River and our water supply.

If you’re unsure, you likely have a septic system if:

• You do not receive a monthly water and sewer bill from your water utility
• You have a well.
• There is a drainfield on your property.
• Still unsure? Contact Gallatin or Madison County Environmental Health services for your property’s permit history.

Wastewater eventually ends up in our groundwater and the Gallatin River. Let’s make sure it’s properly treated and clean. 

Wastewater is produced when you flush the toilet, take a shower, or wash the dishes. This water flows out of your house and through the main sewer line to be treated—either in your septic system or to a sewage treatment plant.

The septic tank stores raw waste long enough for the solids to settle out. Oil, grease, and soap suds float to the top (scum) while organic waste and other heavy solids settle to the bottom (sludge). Bacteria partially digest both scum and sludge. However, undigested solid waste must be regularly pumped from the septic tank to avoid overloading the system.

When separated, liquid waste flows to the drain field for treatment. Wastewater gradually seeps from the drain lines into the ground where soil will filter out the remaining solids and organic matter. Tiny microbes living in the soil break down harmful bacteria and pathogens.

Finally, the leftover treated wastewater percolates into the groundwater. From here, this water will flow back up through groundwater springs to recharge the Gallatin River aquifer, the source of our drinking water.

Malfunctioning septic systems are one the leading causes of excess nitrogen in our watershed. On its way to the Gallatin River, water from rain and snowmelt flows across and through the landscape.

This runoff picks up and carries natural and human-made pollutants, known as nonpoint source (NPS) pollution. NPS pollution in Big Sky includes (but is not limited to), oils from cars, industry/construction runoff, fertilizers from lawn care, pet waste, and older/faulty septic systems. This runoff contains pollutants that contribute excess nitrogen that seeps into our groundwater. Read more about NPS.

Excess nitrogen is the most pressing NPS pollution issue for the Gallatin River. In a healthy river system, nitrogen is occurs naturally and helps stimulate aquatic plant growth. However, it can also feed algal blooms, which, in excess, can cause a cascade of negative effects for aquatic ecosystems.

Wastewater from poorly functioning septic systems is one of the leading causes of elevated nutrients in Big Sky area streams. Contaminated groundwater may end up in your well as overloaded systems leak bacteria, nitrogen, and viruses into the groundwater, spreading diseases and other contaminants to your family or community.

Regular maintenance of your septic system can also save you money. Replacing a malfunctioning system can cost $8,000 to $20,000, while regular maintenance costs about $200 to $400 every three to five years. In addition, malfunctioning systems reduce property values, hamper the sale of your home, and may even pose a legal liability.

• Slow draining sinks and toilets
• Bacteria in well water
• Strong odors
• Bright-green grass over drain field
• Soft ground or excessive wastewater pooling on your lawn

• Perform regular maintenance by cleaning the effluent filter every six months and Get your system inspected annually.
• Pump the tank when indicated by inspections, generally every three to five years.
• Financially plan for when your septic system does become old enough that it needs to be replaced.
• Don’t park cars or drive over the drain field
• Don’t plant trees or deep-rooted plants near your system.
• Keep roof drains, sump pumps, and other stormwater drainage systems away from the drain field.

‘Flushable’ does not mean septic safe. Only human waste and toilet paper are flushable. Refrain from flushing bleach, chemicals, ‘flushable wipes’, tampons, condoms, prescriptions, or other disposables. Disposable means it belongs in the trash! Disposable products will not break down and can overload your septic system, making it more difficult to pump. Garbage disposals contribute additional solid waste that could overload your septic system, so be mindful of that, too.

Taking multiple showers, running multiple loads of laundry, and running the dishwasher all in one day can overload your system and flood your drainfield, which can degrade groundwater quality and back sewage up into your home, requiring costly repairs. Take advantage of our rebates and learn about other ways to save water

Gallatin County Environmental Health Services: For permit information, and applications for new or upgraded septic system installations.

Madison County Environmental Health Services: For permit information, and applications for new or upgraded septic system installations.

Septic Pumpers: State of Montana: List of septic pumpers and inspection professionals in the state of Montana.

Montana Homeowners Septic Guide: More information on homeowners septic system responsibility.

EPA Septic Smart: U.S. Environmental Protection Agency information and guides on septic systems, maintenance, etc.

EPA types of septic systems: U.S. Environmental Protection Agency information on the different types of septic systems.

Montana Well Educated: Montana State University Extension education resources and information on groundwater quality.