What Not to Flush into Your Septic System
A properly functioning septic system is built to manage only human waste, toilet paper, and water. Anything beyond these basic materials risks compromising system performance and potentially leading to costly repairs. According to Penn State Extension, widely circulated products such as wet wipes—even those labeled "flushable"—facial tissues, paper towels, diapers, feminine hygiene products, condoms, dental floss, cotton swabs, cigarette butts, cat litter, and miscellaneous trash are not suitable for septic disposal because they do not biodegrade and can accumulate in pipes or tanks, clogging plumbing and overloading the system.
In addition, kitchen-related items—such as cooking oil, fats, grease, coffee grounds, eggshells, and food scraps—are problematic because they contribute to sludge buildup and may obstruct filters or damage leach fields. Harsh chemicals—including concentrated bleach, chemical drain cleaners, solvents, pesticides, antifreeze, and paint—can kill the essential anaerobic bacteria needed to digest waste inside the tank and destroy the biological balance required for proper operation; these substances may also corrode plumbing materials or contaminate surrounding groundwater. Pharmaceuticals and over-the-counter medications are likewise discouraged—while they may seem benign, they often pass through septic systems relatively unchanged and can harm the microbial ecosystem, posing an environmental risk if they reach soil or groundwater.
These findings are echoed by experienced homeowners and septic professionals on Reddit:
“NEVER flush anything except human waste and toilet paper. Flushable wipes are NOT flushable. Feminine hygiene products are NOT flushable.”
“Don’t pour grease down your drains … discard all food waste, paper products of ANY type … into a trash can.”
Together, these recommendations form a clear directive: only human waste, toilet paper, and water belong in your septic system. Everything else—from grease and food scraps to wipes, pharmaceuticals, and harsh cleaners—should be disposed of via the trash in order to maintain system health and longevity.
