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Q. At our current house we are on a public sewer and have a garbage disposal in the kitchen sink. We're moving to a house with a septic tank and are anticipating a tough transition away from the disposal, as we've been advised against using one with a septic tank. I know that there are disposals on the market that are designed specifically for use with septic tanks. What are your thoughts on them? Are they worthwhile or should we get used to throwing our food waste in the garbage can?
A. Most areas where septic systems are installed have plumbing codes against the installation of garbage disposals. What I frequently see, especially in high end houses, is the builder will have an electrical junction box roughed in under the kitchen sink that can power an instant hot water disposer and/or garbage disposal. When the municipal code inspectors have all gone away and the occupancy permit has been granted, the garbage disposal gets installed.
Garbage disposal manufacturers say that their product installed on a properly sized septic system will work fine. They offer special models of disposals that inject a chemical-- one company call theirs “Bio-Charge”-- that ostensibly aids the system. It’s sort of septic pixie dust and is about as useless as it gets. However it does no harm. The main problem with a garbage disposal on a septic system is the additional raw organic matter that it contributes to the system. That will impact cleaning frequency. A septic system is nothing more than a private sewage treatment plant designed and installed to serve a dwelling or building of a certain size or use. Even restaurants can be on septic systems if they are designed for it. The real killer of residential septic systems with garbage disposals is the amount of animal fats that get into the system. Then fat gets into the dispersal field and seals it from the ground, ruining the ability of the system to percolate gray water into the ground. The septic system is basically a tank, usually about a thousand gallons, buried in the ground near the house, where step one of the treatment takes place and the leach fields, or drywells, where step two, the dispersal of the effluent, takes place. Drawings of modern systems are kept on file by address at the health department for reference. When they work it’s great and no trouble. Periodically, the settled solids in the stage one tank need to be pumped out and carried off site and disposed elsewhere. There is a lot of mystery about septic systems and the greatest mythology surrounds what, when and how they can go bad as a failing septic system can be a life-altering event. The history of septic system installations in this area over the past 40 years or so goes something like this. For a long time-- and a long time ago-- septic systems were installed in a very haphazard manner. The builders or installers would design them virtually any way they wanted and they might work for a few years, or less, then quit. Homeowners were stuck and sometimes systems would end up being little more than holding tanks that required bi-weekly pumping. That’s expensive. And unhealthy. I have personally seen septic systems with nothing more than a 55-gallon drum full of oyster shells stuck in the ground for a dispersal system. Then in the mid-1970’s our local government got tough and now one must have enough capacity on the lot for a second back-up system. They design the systems and watch them be installed. The pendulum swung. There are companies now that specialize in septic inspections known as “pick and shovel” septic tests and those folks know how to locate and expose septic systems. Usually the septic tank is about ten feet or more out from the house, perpendicular to where the main waste line exits the basement or crawl space. The location is usually signaled by the four inch pipe that sticks up out of the ground. But not always. You’ll hear some preach annual septic tank cleaning or every couple of years or so but I say that all depends upon use. If you have a full house ‘round the clock for years on end with a garbage disposer at the kitchen sink that you really shouldn’t have plus family members who hurl things down plumbing fixtures that they didn’t eat first then that system will need careful attention. Whether you add a disposal or adjust to the garbage can will be up to you.