Frequently Asked Questions

hese symptoms tell you that you have a serious problem:

  • Sewage backup in your drains or toilets. This is often a black liquid with a disagreeable odor.
  • Slow flushing of your toilets. Many of the drains in your house will drain much slower than usual, despite the use of plungers or drain cleaning products.
  • Surface flow of wastewater. Sometimes you will notice liquid seeping along the surface of the ground near your septic system. It may or may not have an odor associated with it.
  • Lush green grass over the absorption field, even during dry weather. Often, this indicates that an excessive amount of liquid from your system is moving up through the soil, instead of downward, as it should. While some upward movement of liquid from the absorption field is good, too much could indicate major problems.
  • The presence of nitrates or bacteria in your drinking water well. This indicates that liquid from the system may be flowing into the well through the ground or over the surface. Water tests available from your local health department will indicate if you have this problem.
  • Buildup of aquatic weeds or algae in lakes or ponds adjacent to your home. This may indicate that nutrient-rich septic system waste is leaching into the surface water. This may lead to both inconvenience and possible health problems.
  • Unpleasant odors around your house. Often, an improperly vented plumbing system or a failing septic system causes a buildup of disagreeable odors around the house. sep h it.system? A number of products are marketed with the pledge that they can keep septic systems operating smoothly, correct system upsets, or do away with the need to pump the tank periodically. Chemical additives are strong acids or alkalis, or organic solvents. Biological additives are cultures of harmless bacteria, plus waste-digesting enzymes. These sometimes contain yeast cultures.

lthough some manufacturers of additives have test data showing how their products perform, there has been almost no independent testing of these products in full-sized septic systems. The information that exists does not show improved long-term performance in systems where additives have been used. If a system is not being misused by the homeowner, these products are unlikely to pose a benefit. The amount of material added with each dose of product is very small compared to the biological material already present and working in the tank.

ccasionally a system suffers an upset, when the septic tank bacteria are harmed or destroyed. This can happen if the home is vacant for a long period and the tank receives no fresh wastewater, or if strong cleaning agents are flushed down the drain. After a few days of normal use, the biological system in the tank will re-establish itself. In this situation the biological additives may help speed the recovery of the septic tank.

very septic tank needs to be pumped periodically, because all wastewater contains inert matter that cannot be degraded in the tank. No additive can do away with this need.

  • Check your system annually for leaks and sludge.
  • Have your septic tank pumped by a licensed pumping contractor.
  • Practice water conservation. Repair leaky faucets and toilets. Spread clothes washing over the entire week, and operate only with a full load of laundry.
  • Learn the location of your septic systems. Make a map and keep it handy.
  • Keep a maintenance record.
  • As you use your septic system, sludge will accumulate in the tank. Properly designed tanks have enough space for up to three years of safe accumulation. Once the sludge has reached this level, the separation of solids and scum no longer takes place, and sewage may overflow into the absorption area causing leach field failure. Leach Fields cannot be repaired. They must be replaced and this is very costly. This can be prevented by periodically pumping the accumulated sludge.
  • Do not put substances such as motor oil, gasoline, paints, thinners, and pesticides in drains. These materials may pollute the groundwater and are toxic to the microorganisms that maintain an active septic system. Moderate use of household cleaners, disinfectants, detergents, or bleaches will do little harm to the system, but remember that where there is a high density of septic systems there may be a cumulative impact on groundwater from household cleaners. Fats, grease, coffee grounds, paper towels, sanitary napkins, disposable diapers, and other such items will clog your septic system.
  • Keep automobiles and heavy equipment off the absorption field. Grass cover and shallow-rooted plants are beneficial over the absorption field, but the deep roots of trees and shrubs stress and may plug nearby drain tiles. Do not fertilize the soil above the drain field. Grass on the surface of an absorption field should be mowed regularly to promote evaporation and removal of water through the leaves. This helps prevent water from unnecessarily infiltrating the soil above the absorption field.
  • Remember to consider the capacity of your septic system when installing new appliances or plumbing. Limit the water entering the tank. Use water-saving fixtures. Repair toilet float valves, leaks, and dripping faucets.
  • Yeasts, bacteria, enzymes, and chemicals are sold with the claim of helping septic systems work better; however, there is no scientific evidence that additives are effective. In fact, some cleaners allow the solids in an overloaded tank to be re-suspended and clog the drainage lines. Additives are not an alternative to proper maintenance and do not eliminate the need for routine pumping of a septic tank. Commercial biological additives are not necessary for restarting decomposition after pumping because the sludge residue contains active microorganisms.
  • Learn how to recognize problems with septic systems. For example, unusually lush and green grass over your drain field may indicate trouble. Also, pay attention to slow-draining toilets or drains, sewage odors, or sewage backing up into the house or over the drain field.

The invention of the septic tank is credited to Frenchman John Louis Mouras, who, during the 1860s constructed a masonry tank into which was directed various household detritus from a small dwelling in Vesoul, France, subsequently overflowing to an ordinary cesspool. After a dozen years, the tank was opened and found, contrary to all expectations, to be almost free from solids. Subsequent to collaborations with one Abbe Moigno, a priest-cum-scientist of the period, Mouras was able to patent his invention on 2 September, 1881. It is believed that the septic tank was first introduced to the USA in 1883, to England in 1895 and to South Africa (by the British military) in 1898.

Even now, a century plus later, septic tank systems represent a major household wastewater treatment option. Fully 1/4 to 1/3 of the homes in the US utilize such a system.


septic tank system includes an underground tank and leach field A well designed and maintained concrete, fiberglass or plastic tank should last about 50 years. Because of corrosion problems, steel tanks may only last a decade or less. Most typical is a two compartment septic tank.

The size of the tank will vary depending upon local codes, but a typical tank for a family of four would have a liquid capacity of 1,500 gallons.

'Drawing of a Typical Septic Tank''Drawing of a Typical Septic Tank'

On the left is the input pipe from the dwelling, on the far right is the output pipe to the leach field. The tank itself is water tight and divided into two semi-compartments. This division allows for improved digestion of the waste materials. When the waste flows into the tank, the heavy solids (primarily feces) sink to -the bottom to form a layer of 'sludge'. Lighter materials (grease, fats, small food particles ' etc.) float on the surface forming a layer of "scum'. Between these two layers is a soup of suspended materials and water soluble chemicals (urea from urine and many household chemicals). The division into two chambers increases the efficiency of the system at removing suspended solids. The second compartment receives its "load", or liquid mixture, already substantially clarified (much of the solid material has settled out of the liquid). There is little turbulence in the second chamber either, because the load enters more slowly. Both of these factors allow settling of finer suspended solids than can occur in the first chamber where incoming material acts to churn up the chamber contents.

he process of digestion in the tank is carried out primarily by microbes excreted from our, gastrointestinal tracts (E. coli, for instance). Digestion is an anaerobic process, meaning -that oxygen is not required. Gases (hydrogen sulfide and methane) are produced and must be vented. Basically the same -thing that happens in a septic tank also occurs in our guts and in centralized waste water treatment plants, however a properly operating septic system is probably the most efficient of the three. In the septic system, the gases help to stir the sludge, scum and liquid layers which promotes further digestion of the solids. A properly functioning tank will convert the bulk of solids into liquid waste through the processes of digestion and hence, decomposition.

septic system is well suited to breakdown human excrement, and a well designed, properly used and maintained system is one of the best choices for waste disposal in certain areas of the country. However, there are many potential problems with septic tanks. One of which is that people put a lot more than human waste down their drains. Even simple food items such as too much grease, cooking oil or fat may greatly reduce the efficiency of the system. Household cleaners, paints and other toxics are also toxic to the bacteria which make the system operate properly. Excesses of these chemicals may cause a severe disruption in the system.

utting an excess load on the system when more people are in the house (flushing the toilet, taking showers and otherwise running more water into the system) then the system is designed for can result in materials moving through the system too quickly to be decomposed and contamination problems may result.

here are many considerations to be made before installing a septic tank system. In order- for it to function properly, it is important for the surrounding soil to have certain characteristics, the most important of which has to do with permeability. The water carrying capacity of the soil must be measured before a system can be approved for building and must be known before a proper system can be designed. Usually a percolation test is performed to determine the adequacy of the soil to support a septic system.

nother critical design consideration has to do with the height of the water table. The leach field must have a certain separation from the water table to prevent contamination from occurring. Likewise layers of impermeable "soil' must be a certain depth below the leach field.

here is an engineering modification known as the Wisconsin mound system which may allow the use of septic tank systems in areas previously considered to be unsuitable due to slowly permeable soils (percolation rates slower than 60 minutes per inch), thin soils over permeable bedrock, and permanent or periodically high groundwater tables. Basically the only differences are the addition of a pumping station to pump the tank effluent up to a leach field constructed in a mound on top of the natural soil surface. This system is definitely much more expensive than a traditional septic tank system, but offers a viable solution in regions where the soil characteristics preclude the use of a traditional system.

ecause the proper functioning of the system is so heavily dependent upon the user, there is a tremendous problem particularly back East, with groundwater contamination as a result of inadequate design, use, and/or maintenance. This contamination is predominately microbiological. Microbes, both bacteria and viruses may remain viable much longer underground then when they are exposed to the elements. They are small enough that they may travel with the plume of percolating water from the leach field and contaminate drinking water sources, either groundwater or wells.

he average household of 3 uses 150,000 gallons of water per year, a family of five may use as much as an acre foot, or 325,900 gallons per year. Of this, approximately 1/2 is used indoors and thus goes down the drain into the septic system (the other- 1/2 is used out-of-doors). In other- words, between 200-400 gallons of water (plus wastes) goes into a family's septic tank DAILY. If the system is not properly designed to accommodate these flows, then the sewage will not be properly treated before flowing into the leach field. Problems will also arise if the leach field is in soils which can not absorb the level of flow generated, or- if the soil does not retain the liquid long enough for additional decomposition to occur.




he typical sources of waste water entering a septic system are toilets (approximately 38%), laundry (25%), showers/baths (22%) and sinks/other (15%). Therefore, the potential contaminants must all be introduced into the system from one of these sources. The principal contaminant-type of concern is microbiological (pathogenic bacteria and viruses).

oils which are very permeable (have a rapid percolation rate),

also have a very small capacity to absorb effluent from the leach field and this capacity may be quickly exceeded if the system is not designed to take this into account. Not allowing for soils with little capacity to absorb moisture is a prime reason groundwater contamination occurs, because pollutants tend to move rapidly through the soil with little chance for decomposition.



he typical leach field will be perpetually wet (remember that several hundred gallons of liquid a day enter the tank and thus the field). This moisture encourages the growth of a "slime mat" composed of a variety of microscopic plants (algae) and animals (bacteria, etc.). This slime mat is the final clarifier of the waste water, pulling out left-over nutrients for their own use. They will also decompose, to varying degrees, certain synthetic organic chemicals such as some pesticides and solvents.

any environmental factors (rainfall, soil moisture, temperature and pH, and availability of organic material in the soil) influence the movement and fate of microbes from the septic system through the soil to groundwater. Once out of the French drains in the leach field, pathogenic bacteria will have to compete for food with soil microbes and the microbes in the slime mat underlying the leach field.

hosphorous, a contaminant introduced from many laundry detergents, typically is not a groundwater contamination problem because it is readily taken up by iron, aluminum and calcium naturally occurring in the soil. Urea is converted by the septic system flora into nitrite, nitrate and ammonium. Nitrate may be a groundwater contaminant particularly in soils which are very permeable. Nitrate moves readily through most soils dissolved in water.

etals pose interesting problems. Possible contaminants include lead (from lead water pipes or lead solder- on water pipes), arsenic (found as a contaminant in phosphate detergents), iron, tin, zinc, copper and cadmium. They are not typically a concern in septic systems.

ovement of many organic contaminants such as solvents, cleaners, degreasers and pesticides, through soils is not well understood. There is certainly the possibility for organics, such as solvents, to move with water through the soil to groundwater. Also possible are adsorption onto soil, decomposition by soil microbes or uptake by microbes or plants. The environmental fate of most pesticides has been closely examined, but not from the prospective of subsurface introduction via a septic system.


This depends on the following:

  • Capacity of septic tank
  • Flow of wastewater
  • Volume of solids in wastewater

Volume of wastewater flow is determined by the type and frequency of common household activities. Water conservation practices in the home will help to limit the flow into the system. Use of an in-sink garbage disposal will increase the volume of solids and is best avoided. Care should be given to the type and amount of solids disposed of through a garbage disposal. Please note that biological and chemical septic tank additives are not necessary and do not eliminate the need for pumping.


The table below will give you a general idea of how often you should have your Septic Tank pumped.


Septic Tank Pumping Frequency in Years
Number of Occupants
  1 2 3 4 5 6 7 8 9 10
Tank-Gallons Pumping Frequency in Years
500 5.8 2.6 1.5 1.0 0.7 0.4 0.3 0.2 0.1 --
750 9.1 4.2 2.6 1.8 1.3 1.0 0.7 0.6 0.4 0.3
900 11.0 5.2 3.3 2.3 1.7 1.3 1.0 0.8 0.7 0.5
1000 12.4 5.9 3.7 2.6 2.0 1.5 1.2 1.0 0.8 0.7
1250 15.6 7.5 4.8 3.4 2.6 2.0 1.7 1.4 1.2 1.0
1500 18.9 9.1 5.9 4.2 3.3 2.6 2.1 1.8 1.5 1.3
1750 22.1 10.7 6.9 5.0 3.9 3.1 2.6 2.2 1.9 1.6
2000 25.4 12.4 8.0 5.9 4.5 3.7 3.1 2.6 2.2 2.0
2250 28.6 14.0 9.1 6.7 5.2 4.2 3.5 3.0 2.6 2.3
2500 30.9 15.6 10.2 7.5 5.9 4.8 4.0 3.5 3.0 2.6


Keep in mind that these are average numbers. You may need to have your tank pumped more or less frequently depending on how you use your system. The more solid matter you put in the more often you'll need to pump. It's better to err on the side of caution and pump too often than it is to wait too long and risk a fouled leach field. Having to replace your leach field is many times the cost of pumping.

The following opinions were submitted by septic professionals to Pumper Discussion, an e-mail based forum forum for industry professionals sponsored by Cole Publishing. They also appeared in the February 2005 isuue of Pumper magazine.


Question: We're pretty new to the business. Can anybody tell me how to deal with additives? We've recently had request for them. Is there one additive that's better than another?


I believe that use of additives in the septic tank is detrimental, as they can tend to agitate the scum and sludge layers, creating a "soup" which then flows into the drain field, causing irreparable and permanent damage. I am also starting to think that enzyme-type additives may be of some use when placed straight into a sluggish drainfield, never into the septic tank.

I have a slightly different view than most on this subject. I know that the use of some additives, especially any with surficants or emulsifiers in them, can cause much more harm than good. I also know that many people are going to buy an additive of some sort. I would rather have them buy an additive from me that is not going to harm their system then buy from one of the telemarketing companies at astronomical prices, or buy some miracle cure that claims they will never need to pump thier tank again.

Using an additive on a regular basis keeps them aware that their system requires periodic maintenance and proper care. If they are more aware of how their system operates, they are much less likely to flush items that will clog the system or kill off the beneficial bacteria. Many customers call me once per year when they run out of bacteria. It keeps me in touch with the customer without making annoying marketing calls. In my opinion, this is enough of a benefit in itself to warrant using an additive.

Also, there was an article in a recent issue of Small Flows Quarterly describing a study done by students at a university. Their blind study did show that the septic systems of homeowners using an additive had fewer problems than those who didn't use additives. The margin was small, but significant enough to warrant further research. The author concluded that using a quality bacteria additive may increase the performance of septic systems.

Many studies have been done regarding septic tank additives. I have yet to see one showing any positive effects, other than the sellers profits. Yet I have seen some additives that cause harm. I tell folks not to use additives, but (there's always an exception) only in the case where a household member is on chemotherapy or long-term antibiotics. These would be killing the naturally occuring bacteria, and that is the only time the bacteria would need to be replaced or supplemented.

If someone out there has a solid, unbiased scientific study showing positive effects of septic system additives, please post the details here. All the university-related studied I've seen show no difference between systems with and systems without additives.

Any reputable distributer will acknowledge that use of the product does not take the place of regular system maintenance. Those who support this industry also often times will help the septic pumper develope marketing, sales and suggested use plans for the additives they manufacture. I am not aware of any manufacturer who advertises in Pumper or exibits at the Expo that would recomend against regular pumping.

I think the question is: "How much do I need to makea system work?" What I've been doing here on Long Island is that I deliverit and add a liquid bacteria. This does two things. First, I am with the client every three month, so I get to check the system out, make recommendations on it, and keep on top of any problems.. I do pick up a ton of repeat business, and I get to meet the neighbors, and the whole street knows me and my company. And then I can spend a day on a single block doing work or just soft-marketing my services. Bacteria is a door opener.

Many homeowners want to be involved in maintenance and are absolutely convinces that they should add a suppliment to their septic system. By providing a quality product that will do no harm, we as pumpers can make sure homeowners don't use a product that makes the wild claims we have all heard.

If they are involved enough to keep track of the additive usage, they are more likely to be aware of just what they try to flush into their systems in the first place. It also puts them back in touch with you, the pumper, when they need to order more product.

I have seen what can happen if the wrong chemicals are added to septic systems. There is a local farm store that sold a wetting agent intended for improved spray patterns and coverage when using large agricultural spray equipment. You could actually take a gallon of this stuff and walk out to a pond of standing water in a farm field, pour it into the water, and almost watch the water soak away into the soil.

Someone got the bright idea that this stuff could be added to sluggish septic systems to make them perc better. It worked for about six months, and then the system totally clogged because the wetting agent didn't let the the solids settle out in the septic tank.

New layer...

When dealing with a clogged septic tank that needed pumped asap, Dan arrived sooner than expected and did the job professionally and quickly. He was excellent at getting back to us soon after we called, and always returned subsequent phone calls. He took the time to explain how everything works and provided useful advice. Highly recommended!

— rob b., Los Gatos, CA


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