Understanding Septic Systems

Basic maintenance will help your septic system last longer and perform better.

| September 11, 2008

septic pump-out

Under most conditions, a septic tank will need to be pumped out by a professional every two to five years.


A septic system is the most common way to treat household wastewater if connections to a municipal sewer aren’t available where you live. But few people who rely on septic systems understand how they actually work. And without correct knowledge, you’re open to misinformation or accidental mismanagement that could cost you lots of money.

The word septic means “absence of oxygen” and that's the state of affairs in the first part of every septic system — the tank. This is where raw sewage is broken down by anaerobic bacteria, liquefying most of the solids. Indigestible bits settle out into the bottom of the tank, a bacterial scum develops on the surface of the sewage, and excess liquid flows out of the tank into a network of perforated pipes buried underground. This area is large, and extends beyond the tank. It's called a leaching bed, or weeping bed, and it's the place where 90 percent of sewage purification occurs as nutrient-rich wastewater dribbles out of holes in the pipes. After this happens, soil microbes, insects and roots of grass purify the water. (Don’t plant vegetables in this area.)

Keep Things Flowing Smoothly

Septic systems can function for decades, as long as the soil around the perforated pipes remains porous enough to allow wastewater to drain away. But after the soil loses this porosity, sewage backs up and you’ll have a major problem.

Routine maintenance of your septic system is aimed at retaining the all-important porosity of the leaching bed, and this is the reason septic tanks need to be pumped out every two to five years by a professional (gases produced by a septic system can be deadly). Because the septic digestion of incoming waste is never complete, an indigestible sludge slowly builds up in the bottom of the tank. And while this is normal, it means the effective size of the tank is constantly getting smaller. If tank capacity is reduced enough, solids are forced out into the leaching pipes where they'll clog the soil and ruin your system.

Few people realize how bad washing machine lint is for septic systems. The small particle size of lint means that it doesn't settle to the bottom of the tank. If you're washing machine filter allows enough lint to slip past, it'll clog your leaching bed prematurely.

When the Water is Rising

The first thing to look at if your septic system goes bad is sewage loading immediately before the problem occurred. Did you have a lot of house guests? Have you been doing a lot of laundry? Backed up main drains or a swampy back yard might be caused by temporary overloading of the system. Limit water use for a few days and see what happens. If the problem remains, you could have a congested leaching bed, though not necessarily.

8/6/2014 3:07:03 PM

There are 2 different opinions on this page about the merits of aerobic vs anaerobic bacteria in septics. Which is best for soil? For de-clogging failing systems?

leeann coleman
8/8/2011 1:54:28 PM

My septic system has been in continuous use since 1969. I have a small house, and a small leaching field. Luckily, the original owner/builder had the foresight to build a separate gray water system out back (which today cannot be built under current code). I credit that for the long life of my system. Our septic guy, who I see once every couple of years for pump-outs has only one time had to do anything else, and it was to remove toilet paper that had clogged a line after a large barbeque - easy, easy fix! The trick is to make sure nothing goes down the toilet except human waste. Septics are completely natural systems, so it goes without saying that anything unnatural that goes in there will disturb the process. Think simple.

jan steinman
8/3/2011 12:35:37 PM

Why did this article not mention humanure? Septic systems are simply wasting valuable nutrients that should be put back onto the land, NOT fed to bacteria in a tank!

7/5/2011 8:35:58 AM

It amazes me how these forums can be used as marketing forums for things like "Flow" and "Sledgehammer". The purpose of septic systems is to protect the groundwater from contamination; that includes non-sewage additives such as solvents, paints, etc. Products claiming to break down the sludge in septic tanks might so that, but also allow the micro-particles (solids) to be flushed out into the leach-lines eventually clogging the pours in the soiland failing the systems. I have yet to see any health department or contractor suggest the usage of these products. Be sure to check with your local health department to see if the "miracle remedy" you have been you have been duped into is either reccomended or approved. BTW, the assertion that graywater systems are not regulated is an untruth

3/24/2009 2:14:37 PM

The word, "septic," means "full of bacteria," not, "without oxygen," as claimed in the article, but in a septic tank, there's not a lot of chance for oxygen to get in and that's why there's a build up of poisonous gases, which can be fatal if inhaled. Because it is the bacteria that purify the water, be sure not to harm them. In addition to the other commenters' suggestions, be aware of what you are using to clean your tubs, sinks and toilets. Bleach and bleach-containing products kill bacteria. Don't use anti-bacterial soaps. Anti-bacterial soaps, by the way don't kill the bacteria on your hands, unless you soak your hands in them for at least 15 minutes, so the addition of antiseptics in soap is a marketing gimmick. You can extend the time period between pumping the system by only using the septic for urine and feces. Don't use the toilet for a trash can. If you blow your nose, even on tp, put that in the trash can. Some food will make it down the kitchen sink, but use a strainer and toss as much as you can into the composter. You already know about laundry. Never, ever, drain grease or oil down the sink. I dump especially dirty, greasy dish water in the yard. Oh and, sorry fellas, contrary to the claim, peeing outside may be more convenient and save cleaning, but it doesn't save the septic, unless you pass a lot of stones.

12/9/2008 9:52:13 PM

I've just bought a home that's on septic and want to build a vegetable garden in raised beds in the yard. There won't be any digging involved but the wooden beds will be located above the septic system. Does anyone know if this can cause problems to the system? Thanks a lot for any info.

clint marchbanks_1
9/19/2008 8:50:36 AM

the bleach used in the washing machine can kill the bacteria in the septic tank and the detergent doesn't help either. this is grey water and doesn't have to be connected to the septic system. it is best to run this grey water in a different holding tank. grey water is not regulated by the local county environmental department, so you can drain this grey water in a 50 gallon drum or the pasture, yard or whatever. Add yeast to your septic system to keep the bacteria active.

dave larson
9/19/2008 7:35:37 AM

Responding to the comment on water from clothes washers clogging a system with lint, I might suggest that a grey water system channeling the drain from the clothes washer to a garden or orchard might be a positive alternative. Here in the Chihuahuan desert, we try to use water twice. Of course, this choice will necessitate care in soap selection and avoidance of bleach. Our trees love the extra water.

9/18/2008 6:46:18 AM

Interesting. This article reads as if my local Chamber of Commerce wrote it for the only septic cleaning company within 200 miles. I have been using an organic liquid called FLOW which I have ordered from Gardens Alive for years. When I rebuilt a few years ago, I called the local company to check and clean out my system. Ther4e was maybe 12 inches for them to clean out. Of course the septic cleaner tried to get me to sign up for regular cleanings and told me that FLOW was useless. Interesting. I have no standing water, the tank was not even half full after over 10-15 years of having been cleaned, and there is never any smell from the exhaust pipe! No thanks! I do not care to fall for the "big vaccum cleaner service" with FLOW around!

winter star
9/17/2008 3:51:33 PM

There many more simple, gravity model septic systems, that still function decades later, because owners use them properly---avoid clay-based cleaning agents, avoid putting in any antibacterials, etc. It is a shame that technology-laden models, far more expensive, have only shown that the added technology helps them fail faster, pollute more. The industry has been working on strangle-holding to keep the inefficient models going--they make big money. It takes lots of concerted efforts to get rules changed to allow more sensible alternatives.

winter star
9/17/2008 3:47:01 PM

Septic systems as commonly used,are guaranteed to fail, eventually. They are also guaranteed to eventually pollute ground and water sources nearby. Anything that can help keep the system aerobic, helps break things down, helps keep system clear longer. Many products allowed to go into a septic system also help clog it. Using biodegradable products; liquid soaps and detergents, help keep the system going far longer than the dry powdered Disinfectants kill bacteria in the system, as they do on your skin--so these will harm the septic system. Small amounts monthly do little damage, while daily or weekly use more rapidly damages bacteria counts in the system. Aerobic bacteria need oxygen, break down solids faster, have less disease-causing capability. These will only grow where oxygen is--that is, they will stay within the waste system if oxygen is supplied there, and only within the top few inches of soils in the leach field. These cultures are far less likely to contaminate deep soil or water. Anaerobic bacteria do not need oxygen, can break down solids, but are more often also disease-causing. These will not grow if oxygen is present. These cultures WILL migrate though deeper soil and into water, where oxygen is bound by hydrogen. These are the ones that cause septic systems to eventually contaminate far-reaching swaths of ground and water tables. There is a septic system additional component to fix this: The Sludgehammer, http://www.sludgehammer.net/ That aerates the tank continually, uses specific aerobic bacteria to insure through breakdown of solids. This system has proven to rehabilitate totally clogged leach fields and the tanks. These cannot undo decades of clay deposits in septics though. But most cloggage is due to biological solids--for these, Sludgehammer excels! But, you will have to either lobby your health department and legislators to get rules changed to allow these, or, do it under the table, in some areas [WA

9/15/2008 9:06:10 PM

In the mid 1980's in Royal Oak MI a house was discovered still on a never maintained septic system. Unfortunately the occupants had been billed for city sewer service since 1923.It took over two weeks to calculate the refund and compund interest due to the resident for this error. The city did not charge them for the sewer hook up either!

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