What Not to Flush or Put Down the Drain if You Have a Septic System

Most people living on city sewer can flush or drain almost anything without consequences. Septic system owners don't have that luxury. Your tank is a contained ecosystem — a living system of bacteria that breaks down waste. Introduce the wrong substances and you kill that ecosystem. Put in solid materials and you physically clog your drain field. Either failure leads to the same result: costly repairs or full system replacement.

The good news is that protecting your septic system requires only minor habit changes. Here's everything you need to know about what to keep out of your drains.

Items That Will Physically Clog Your System

These items don't break down in water or decompose in your tank. They accumulate in your pipes, your tank, and eventually your drain field — where they can cause irreversible damage:

• "Flushable" wipes — Despite the label, these do not disintegrate like toilet paper. They're one of the leading causes of septic clogs and pump-out service calls.
• Paper towels — Far thicker than toilet paper and designed not to fall apart when wet.
• Feminine hygiene products — Tampons, pads, and applicators do not decompose and will clog your system.
• Cotton balls and cotton swabs — These accumulate in the tank and eventually pass through to the drain field.
• Dental floss — Wraps around other debris and creates nets that trap solid material.
• Condoms — Non-biodegradable and will clog pipes and accumulate in the tank.
• Diapers — Never flush, regardless of whether they're labeled biodegradable.
• Cat litter — Even "flushable" versions clump in water and clog pipes.
• Cigarette butts — Contain toxic chemicals and don't break down.
• Medications and pills — Don't biodegrade properly and can disrupt bacterial balance.
• Hair — Accumulates over time and can form clogs in pipes leading to the tank.

Chemicals That Kill Your Septic Bacteria

Your septic tank works because of living bacteria. These microorganisms break down solid waste and keep your tank functioning. Introduce the wrong chemicals and you kill the bacteria — leaving solid waste to accumulate rapidly and overflow into your drain field.

• Chemical drain cleaners (Drano, Liquid-Plumr, etc.) — Designed to dissolve organic material, including the bacteria in your tank. Use a drain snake or enzyme-based cleaner instead.
• Bleach in large quantities — Small amounts of diluted bleach from laundry are generally fine, but pouring bleach directly down a drain or using highly concentrated bleach cleaners can kill tank bacteria.
• Antibacterial soaps and cleaners — Marketed as killing 99.9% of bacteria. In your septic system, that includes the bacteria keeping your tank functional. Opt for regular soap.
• Paint, paint thinner, and solvents — Highly toxic to tank bacteria and can contaminate groundwater.
• Motor oil and automotive fluids — Never pour these down any drain. Toxic and non-biodegradable.
• Photographic chemicals — Highly toxic and will disrupt bacterial balance.
• Pool chemicals — Chlorine and other pool treatments are designed to kill bacteria.
• Large amounts of disinfectant cleaners — Routine cleaning is generally fine; periodic deep cleans with heavy disinfectants are not.

Food Waste and Garbage Disposals

Garbage disposals are a controversial topic for septic owners. They don't directly damage your system, but they significantly increase the solid load entering your tank — often requiring you to pump 1–2 years sooner than you otherwise would.

• Grease and cooking oil — These solidify in your pipes and tank, creating stubborn blockages. Pour cooled grease into the trash.
• Coffee grounds — Accumulate in the tank and don't break down well. Compost them instead.
• Eggshells — Grind into fine particles that accumulate in the tank over time.
• Starchy foods (pasta, rice, bread) — Expand when wet, creating a thick paste that can coat pipes and drain field perforations.
• Fibrous vegetables (celery, asparagus, artichokes) — Can tangle and create blockages.
• Bones and hard food waste — Do not decompose in the tank.
• Fruit pits and seeds — Same issue: hard, slow to decompose.

Things That Are Safe to Use with a Septic System

Being septic-safe doesn't mean living without modern conveniences. Most normal household activities are completely fine:

• Regular toilet paper — Breaks down quickly in water; the standard single-ply and 2-ply options work well
• Regular soap and shampoo — Fine in normal quantities
• Dishwasher detergent — Use the recommended amount; avoid overloading
• Laundry detergent — Spread laundry loads throughout the week rather than doing multiple loads in one day
• Normal amounts of household cleaners — Periodic bathroom and kitchen cleaning is fine
• Enzyme-based drain cleaners — Safe for septic systems and effective for clearing minor clogs

Warning Signs You've Already Damaged Your System

If you've been unknowingly putting harmful items into your septic system, watch for these warning signs:

• Slow drains throughout the house — Not just one fixture, but multiple sinks and tubs draining slowly
• Gurgling sounds from drains or toilets — Air trapped by blockages
• Sewage smell inside the home or near the tank/drain field — Indicates gases backing up
• Wet, spongy, or unusually green grass over the drain field — Effluent surfacing
• Sewage backup in sinks, tubs, or toilets — Advanced stage of failure

Any of these symptoms warrants a call to a septic professional. Early intervention is always less expensive than waiting until the system backs up or the drain field fails completely.