Septic System Safety

A septic system treats household wastewater underground. Properly maintained, it works quietly for decades. But the tank holds poisonous and explosive gases, collapsed lids and open tanks have killed people and children, and poor care can contaminate your well and yard.

• Homeowners
• Renters & Landlords
• Parents
• Septic Service Workers

How a system works

• Wastewater flows from the house into a septic tank, where solids settle and scum floats. Bacteria break down some waste.
• Liquid flows to the drainfield (leach field), where soil filters it. Some systems use pumps, alarms, filters or aerobic treatment.
• The tank has access lids or risers for pumping and inspection. See also Well Water for water supply near septic systems.

Hazards

• Toxic and explosive gases: hydrogen sulfide, methane and carbon dioxide in the tank can overcome a person in seconds. Never enter a septic tank, even to rescue someone. Tanks are confined spaces. See Wells, Cisterns & Septic Tanks: Hidden Dangers at Home and Confined Spaces.
• Falling in: rotted, cracked or unsecured lids can collapse under a person, child or mower. Keep lids secured.
• Pathogens in sewage and backups. See Sewage & Wastewater Exposure.
• Electrical hazards from pumps and alarm panels in wet places.
• Collapse of the soil over old tanks when driven on.
• Contaminated water if the system fails near wells, lakes or streams.

Safe care

• Keep lids on and locked or secured with screws, and keep children away. Replace damaged lids immediately. Mark the tank location so no one drives or builds on it.
• Hire a licensed septic professional to inspect and pump. Most households need pumping about every 3 to 5 years, depending on tank size and use. Keep records.
• Never open the tank yourself or lean over it. Do not smoke or use flames near it.
• Don't drive or park on the tank or drainfield, and keep trees and deep-rooted plants away. Direct roof drains and sump discharge away from the field.
• Conserve water: spread out laundry, fix leaks and use efficient fixtures to avoid overloading the system.
• Flush only toilet paper and human waste. Do not flush wipes (even "flushable"), feminine products, diapers, grease, medications or chemicals. See Medication Safety.
• Limit harsh chemicals, paint, solvents, bleach and drain cleaners that kill helpful bacteria. See Household Chemicals.
• Don't use additives that claim to eliminate pumping; they are not generally recommended.

Signs of trouble

• Slow drains, gurgling pipes or sewage backups in the house.
• Odors, wet or spongy areas, or unusually lush grass over the drainfield.
• A high-water alarm sounding.
• Contaminated well water tests. See Well Water.

Call a septic professional. Keep people and pets away from surface sewage, and clean up with proper PPE or hire a professional.

Septic safety checklist

• Lids are intact, secured and out of children's reach, and the tank location is marked
• Nobody enters or leans into the tank, ever
• The system is inspected and pumped on schedule by a licensed professional
• No vehicles or structures sit on the tank or drainfield
• Only toilet paper and human waste go down the toilet

Last updated: October 8, 2026