Chemical drums found during a home inspectionSeptic Tank Maintenance: Other Chemicals That Should NOT Be Flushed into a Septic Tank

  • CHEMICALS, KEEP OUT OF SEPTICS-2 - CONTENTS: List of other chemicals & substances that we have seen dumped into septic systems and in one case, into a well - don't do this!Do not use septic tanks, wells, even abandoned wells and septic tanks to dispose of chemicals
  • POST a QUESTION or READ FAQs about septic system chemicals and about using septic systems to dispose of certain chemicals and substances that may harm the drainfield or contaminate the environment

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What items and chemicals are NOT safe to flush down the toilet and into a private septic system besides normal household cleaners and household chemicals?

This document explains how to extend the life of the septic system by being careful about what goes into it.

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OTHER CHEMICALS TO KEEP OUT OF SEPTIC TANKS- Effects of Other Chemicals Flushed Into a Septic Systems

Used motor oil stored for recycling - Canyon Auto Tucson (C) Daniel FriedmanAlso see CHEMICAL CONTAMINANTS in WATER for a discussion of chemical contaminants in drinking water and see WATER TESTS, CONTAMINANTS, TREATMENT.

  • Chemicals, Oils, Paints: Do not flush these chemicals into the septic system in any quantity:
    • Furniture polish
    • Oils such as used motor oil or unwanted cooking oil - photo at left, courtesy Canyon Auto, Tucson AZ.
    • Paints of any kind, latex, oil, alkyd, acrylic, water-based
    • Pesticides
    • Photo chemicals
    • Thinners (such as paint thinner)
    • Varnishes
  • Antibiotics and Septic Systems: Normal use of antibiotics by occupants in a one or two family residence with a septic system will not harm the septic tank or fields.

    High levels of discharge of antibiotics in urine and body waste from many building occupants using such drugs, such as at a nursing home with 50 residents and an onsite septic system, can kill bacteria in the septic tank and leach field and thus may indeed be a problem for such facilities. See DRUGS INTO the SEPTIC TANK? for details.
  • Dishwasher detergents: see Dishwasher & Laundry Detergents Containing Phosphates & Surfactants for a discussion of the effects of phosphates & detergents on the environment.
  • Hydrochloric acid HCL poured into a well: a reader explained that his plumber poured several gallons of pure HCL into the well to attempt to free a pump that seemed to be stuck in the well casing. The plumber eventually got the pump free - we're not sure the hydrochloric acid was what did the trick - the pump may have been stuck at the pitless adapter which protrudes into the well casing.

    In any case the plumber has contaminated the well and worse, probably s/he has contaminated the local aquifer with a toxic chemical. We were left with no advice but to hope that dilution will eventually reduce the effect of this stupid move, and that the owner should test his well water for HCL.

    Since the owner and plumber ran lots of water to "flush out" the well, they've moved at least some of the acid into the owner's septic system and local groundwater where it contaminates the area further. Our opinion was that it was probably better to move the HCL as much as possible out of the well by any means rather than contaminate the aquifer for this well and perhaps for the neighbors.
  • Illegal Drug Manufacturing and Septic Systems: Anecdotally we report on a septic system in New York near the Taconic State Parkway was connected to house in which was operated an illegal drug manufacturing operation - perhaps a "meth lab". So much drug-production-related contaminant was flushed down house drains that the workers contaminated their own well and poisoned themselves.
  • Laundry detergents & soaps used in washing machines & dishwashers are discussed separately at WASHING MACHINES & SEPTIC SYSTEMS
  • Motor oil poured into a drinking well: at a home inspection we discovered two well casings near a driveway. One was a well that was in-use providing water to the home.

    We noticed that the other casing was un-capped and asked the property owner what was up. He explained that he did a lot of work on his own cars and trucks, and that when he changed the oil, he figured that a great way to dispose of unwanted motor oil was to dump it into the old un-used well.

    Do not dump motor oil into your well. You'll contaminate the local aquifer. Used motor oils contain a number of highly toxic substances such as heavy metals. Take used motor oil to almost any garage or gas station where they are required to dispose of it legally and safely. (They may charge you a small fee.)

    This is a great example of why unused water wells should be abandoned properly, including sealing the well against surface- generated contaminants.
  • Pesticides and Septic Systems: people who need to dispose of un-used pesticides should not put them in building drains or toilets. In the U.S. contact your state department of environment or local health department to find the nearest local hazardous waste disposal station where you can usually drop off unwanted chemicals, paint, etc., often at no charge.
  • Subtle phthalates contamination of groundwater and wells from phthalates: in a compelling article in the New York Times in July 2009 Nicholas D. Kristof reported on the possible hazards of phthalates, chemicals that can leach into their contents and thence into the environment from some plastic food or water containers, or even toys.

    While we have not found any research whatsoever that tests for the appearance of pthalates in septic systems and the ground water into which septic effluent ultimately appears, we recommend prudent avoidance of phthalate containing plastics for foods or beverages.

    Mr. Kristof pointed out that "These are ubiquitous in modern life ... -- and many scientists have linked them to everything from sexual deformities in babies to obesity and diabetes."

    Readers interested in the subtle but powerful effects of hormone mimicking chemicals and endocrine disruptors that appear in the environment, their sources, effects, and risks, should also see Our Stolen Future, Theo Colborn, Dianne Dumanoski, and John Peterson Myers.


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