Septic System Brochure


A properly operating septic system is a vital part of many homes located in rural areas. However, the septic system is often the last thing on the mind of a homeowner until there is a problem with the system. When a home is purchased, the big question is, Will I have trouble with the system after I move into the home?

Unfortunately, there is no absolute way to predict how long a septic system will last or if it will be able to handle an increased load. A septic inspection, however, can yield useful information on the condition of the system as it exists when the system is inspected. While predicting the future with regard to the septic system is not part of any septic inspection, the inspection often uncovers defects in the system which can save the purchaser unexpected expense. There are many different types of septic systems ranging from what are called conventional in-ground systems to sand mounds and from spray irrigation systems to stream discharge systems. There are also seepage pits, cesspools, and homemade systems. This booklet is not intended to cover every situation, but is intended to give the homeowner an understanding of the concept of how a septic system works and a better understanding of a septic inspection.


Let’s see how a typical septic system is designed. In the most basic terms, a typical septic system usually consists of a means of separating the liquid material from the solid material and an area where the liquid material can be disposed.

The solid-liquid separation is usually accomplished in what is called a treatment tank. The treatment tank is a relatively large structure typically made of concrete. The approximate size for a residence is 1000 to 1500 gallons. The solid material and liquid material enter the treatment tank by means of the drain pipe from the house. In addition to separating the liquid material from the solid material, the treatment tank also provides partial treatment of the septic waste through biological action within the tank. The solid-liquid separation is accomplished by the use of baffles within the tank. The inlet pipe is usually located at one end of the treatment tank and the outlet pipe at the other end. The normal liquid level in the treatment tank is at the level of the outlet pipe. The solid material that is heavier than water sinks to the bottom of the tank where biological breakdown occurs. Any solid matter that floats is prevented from going out the outlet pipe by means of an outlet baffle which extends just below the surface of the water.

In a standard septic treatment tank the biological action is from anaerobic bacteria, that is bacteria that multiply under conditions where little or no oxygen is present. Not all of the solid material in a treatment tank can be broken down by microbiological action. So over time, these solids build up inside the treatment tank. Regular pumping of the treatment tank removes these solids and allows room for additional solids to enter the tank. When a septic tank is not cleaned frequently enough, the solids from the treatment tank begin to flow out of the treatment tank and into the area where the liquid is disposed. Solids in this area have no place to go and cause plugging of the pores of the absorption area. This lack of proper maintenance can greatly reduce the capacity of the septic system to dispose of waste and will cause eventual failure of the system.

The old adage “If it ain’t broke don’t fix it” DOES NOT apply in this case. It would be much better to apply the saying “An ounce of prevention is worth a pound of cure.”

How often should a septic tank be cleaned or pumped? The frequency for pumping a septic system depends on a number of factors; the average frequency is between two and four years. You can, in some cases, abuse a septic system and neglect to pump it for 10 or 20 years without any apparent problem. This would be like driving your automobile for 50,000 miles without changing the oil. You might get away with it, but you would certainly cause undue wear and tear on the engine. The same is true with a septic system. You may get away with not pumping the system for many years, but you will pay for it in the end by having to replace the absorption area.

Absorption Area

Let’s move out of the septic tank and follow the liquid to the absorption area. While the treatment tank provides some treatment of the septic waste, it does not get rid of harmful bacteria and viruses, so further treatment of the waste is necessary. If soil conditions are adequate, this further treatment of the septic waste can be accomplished in the absorption area by biological action which takes place in the presence of air. Such microorganisms are known as aerobic.

There are many types of absorption areas, drain fields, seepage beds, and sand mounds. As stated earlier, this booklet is not intended to cover every situation, but is intended to give the homeowner an understanding of the concept of how a basic septic system works.

The in-ground type of system uses a series of perforated pipes located below the ground surface. These pipes are placed in a bed of crushed stone or aggregate. The sewage flows over the crushed stone or aggregate into the underlying soil. The condition of this soil determines how well your septic system will operate and how large the absorption area needs to be. If the absorption area is too small and the soil is too tight as with clay soils, the liquid cannot soak into the soil fast enough causing the waste to either back up into the home or emerge at the ground surface. An early sign of waste emerging at the surface is “lush growth.” The saying “that the grass is always greener over the septic tank” isn’t true when it comes to a properly operating septic system.

In areas where the soil is too loose, the waste will quickly flow through the soil not allowing time for the complete biological treatment of the septic waste. This untreated septic waste may eventually contaminate underground water sources.

When the soil conditions are right, an area of active microorganisms is formed where the waste enters the soil. As the waste slowly percolates through the soil the microorganisms continue to grow and feed on the harmful bacteria and viruses in the septic waste. The underlying soil continues to absorb and filter the waste. Four feet of soil is all that is needed to treat the septic waste in good soil conditions.

What happens when the soil around a septic system is saturated with water from other sources? When the septic waste encounters soil saturated with water, the biological action which destroys the harmful bacteria and viruses is inhibited and the saturated soil along with the surrounding water becomes contaminated. This contaminated water keeps moving and spreading until it comes into contact with the underground, water bearing aquifers that may be used for drinking water supplies. Contaminated water eventually results.

Soils that drain too fast or have evidence of seasonally high water table can be helped in their treatment of septic waste by the construction of elevated sand mounds. In an elevated sand mound the waste is treated inside of a constructed bed of sand and stone prior to contacting the natural ground surface. Pump tanks or dosing tanks are usually used with sand mounds to control the flow of liquid waste into the sand mound. In many cases the sand mound is also uphill so the use of a pump becomes mandatory.

Can septic waste ever be discharged into a stream? Some recent advances in household septic systems employ additional filtration and chemical treatment of the septic waste. These systems then are able to dispose of the septic waste above ground or into a stream since the harmful bacteria and viruses are destroyed by chemical means. Special permits are generally required for such systems.

What about cesspools?

Older systems often employ a variety of approaches to dispose of septic waste, some more effective than others. Cesspools, seepage pits, and leach pits are just a few of these types of systems. Most of these older systems were installed prior to permits being required. They generally consist of some kind of masonry structure located beneath the ground. The masonry is often concrete blocks or bricks that have been assembled with spaces between them, the bottom of the pit is generally soil. Crushed stone absorption areas are sometimes added to these systems but are not always included with the system.

Since these older systems were installed before septic regulations were in place, they were often constructed without regard to soil conditions or percolation rate. When they were installed in suitable soil they may work effectively for a long time. On the other hand, systems that were installed in unsuitable soils may contaminate ground water or fail in other ways. When such systems require renovation, they usually will need to be replaced with a properly permitted system, due to local regulations.


From this brief description you can see that most of the components and working parts of a septic system are underground and are not naturally visible. Inspecting a typical septic system then presents a challenge.

A choice needs to be made as to how far one wants to go to investigate a system. In nearly all cases it is impossible to check all of the septic system components as this would require unearthing the tank, absorption area, distribution system, etc. If this is done, there is a risk of damaging the system and ruining the landscaping of the property. In addition, the soil conditions change over time due to both natural and man made alterations. Soil suitability testing which is discussed later could be performed, but is usually impractical in a typical real estate transaction.

Considering the past history of a septic system is useful, but it should be noted that a system which has worked fine for years may over time fail with little or no warning. All septic systems have a finite life span, and inmost cases it is impossible to predict if the system will last 3 or 300 years.

A non-invasive inspection of a septic system is often a good starting point for helping to determine the condition of an existing septic system. The following procedure is used by Suburban Property Inspections. Other companies may or may not follow this same procedure, and since there are many variations in septic system design and function, each inspection is likely to be unique in its own way. Non-invasive inspections leave the soil virtually undisturbed and do not alter the system in any appreciable way. Any available, readily accessible access caps are removed and the liquid level inside is observed. The water inside the home is run for a minimum of thirty minutes. During this time the liquid levels in the access pipes (if any) are observed and the absorption area is examined for seepage or lush growth. The technician relies on visual signs for detecting any defects in the system. Since the soil is undisturbed this kind of inspection can be performed without damaging the lawn or risking the damage caused by digging up parts of the system. Some relocation companies require that a non-invasive inspection be performed.

While the water is running inside the home the toilets are each flushed and are observed for proper operation. The drain lines that are visible inside the home are followed to determine if there is more than one system at the property. Some older systems separate the gray water drains from the black water drains. The gray water drains may at times discharge to daylight. This is likely a violation of local ordinances. In some localities, gray water daylight drains are so common they are largely ignored; other areas may not be so lenient. Septic waste by most definitions includes waste water that may contain any kind of bodily fluid or waste; this would include wash water, bath water, or toilet water. On the other hand, water that enters the basement due to naturally saturated soils is not considered septic waste. Such water can be piped to daylight or pumped to the surface by means of a sump pump. Bear in mind each locality is able to set their own standards. Therefore, to be sure what is allowed in your area, you will need to check with your township, city, or county authorities.

If the absorption area is located and if the soil conditions merit it, a probe bar is used to check the amount of moisture in the soil and absorption area. Saturated soil in or around the absorption area usually indicates a problem. Such wetness may be accompanied by a distinct septic smell or lush growth; however, this is not always the case.

A liquid level that is above the stone is generally considered a defect in a system, though it should be realized that such systems may “work” for the current owner.

Why the dilemma?

There are several reasons why an absorption area may have liquid above the stone. One is that the absorption area has served its useful life span and is no longer able to allow waste to enter the surrounding soil. This may be due to organic material plugging the soil pores which underlie and surround the stone of the absorption area. In such cases, liquid above the stone in the absorption area is an early sign of system failure and breakthrough to the surface will eventually follow. A second reason can be overload of the system. This may be due to leaks in the plumbing of the home, an excessive amount of water usage in the home, or an undersized system. Since on-site septic is often accompanied by on-site water with no means of metering the water, it is often difficult to determine if overload is the reason for the flooded condition of the absorption area. A third reason is high water table. While high water table with no septic breakthrough at the surface might seem to be acceptable at first, such is not the case. When the septic waste does not have the four feet of arable soil for renovation of the waste, ground water contamination usually occurs. Once the bacteria and viruses are in the water table they can survive with little renovation occurring in the soil. Such contamination can travel a considerable distance to water supplies or streams.

When one portion of an absorption area is flooded while the rest is dry, the problem may be less severe and may be a matter of re-leveling the distribution box. In other cases, such as what is known as a serial distribution system, the design is intended to cause the first portion of an absorption area to flood prior to going into the next portion. Such designs are not common in most areas of the country.


How does weather affect a septic system? Since homes are sold in all seasons of the year, septic inspections need to be performed in all kinds of weather. Frozen ground and snow cover may considerably limit the amount of information obtained by a septic inspection. Heavy rainfall contributes to water in the soil and, depending on the grading around the absorption area, can cause additional water in the absorption area. Ideally, the grading should be such that rain water is diverted away from the absorption area. Inspections performed in less than ideal weather will provide less useful information than those done under ideal conditions. The septic inspection is limited to visual observations made the day of the inspection. Inspections performed on other days may yield different results. The septic system, however, should be able to work properly under all normal weather conditions. Severe weather conditions such as flooding may make a system temporarily unusable and can cause damage to the system. Inspections performed at such times would not represent the normal condition of the system. The inspector, however, is limited to what he can observe while he is at the property and is not there to attempt to predict how the system will perform at other times.


How is the soil tested for suitability? Soil suitability is rarely a part of an on-site septic inspection. However, should the system be failing, the soil suitability testing would need to be done in order to install a replacement system. Each area has their own standards for testing soil suitability; most areas employ a procedure similarity the following. Usually a “deep probe” is performed by digging a seven foot deep trench with a backhoe. A soil specialist then looks at the soil layers for telltale signs of seasonally high water table as well as to assess the visual suitability of the soil for drainage characteristics. Fractured rock may allow drainage that is too fast for proper renovation of the waste, while a seasonally high water table that is too close to the surface may indicate that ground water contamination will result from a septic system being placed below the surface of the ground in that area. Obviously it may be necessary to dig and examine many “deep probes” prior to finding suitable soil.

Once a suitable “deep probe” has been performed the next step is to have a “perc test” done. Here a series of holes are dug and after proper conditioning of the soil the holes are filled with water and the rate of drainage into the soil is measured. Soils that drain too slow may not be able to handle the needed quantity of liquid waste, while soils that drain too fast may not allow enough time for the waste to be renovated and ground water contamination will result.

The data obtained from the “deep probe” and “perc test” are compared to state or local regulations. These regulations usually dictate what type of system if any can be installed at a property.

Can a property have totally unsuitable soil? Yes, in some cases there may be no place to install a system on a property. Where this is the case and a house already exists on the property, connection to public sewer or the installation of holding tanks may be the only option short of vacating the home.

What are holding tanks? Holding tanks are, as the name implies, used to hold the waste until it can be removed from the site. Removal is typically done by pumping the waste into a truck and hauling it to a disposal facility. The cost of using a holding tank system can be excessive.

The Buyer’s Point of View

As a buyer where might you run into a problem even after a satisfactory septic inspection? All septic systems have a limited capacity to handle waste. Problems with septic systems that show no defects during an inspection most often occur when an increased load is put on a septic system by the new owner. For instance, an older person may occupy a large home for many years with no septic problems. A family of three or four may purchase the home and use three or four times the amount of water. The septic system may not be able to handle this increased load and subsequent failure of the system occurs.

The age of the system should also be considered. If the system has been in use for 20 years or more without major renovations, such renovations should be anticipated. Questions you might consider: Is public sewer available if I need to connect to it? Do I have sufficient, suitable land to put a replacement system if it is needed?

What if the property is vacant when it is inspected?

Vacant properties further limit the inspection of the system since the water usage is nil. For best results we recommend that the realtor, seller, or buyer run the water for one hour per day for a period of one week or more prior to the inspection to help duplicate an occupied condition. Additional running of the water is available during or prior to our inspection for an additional fee. We must be notified that this service is desired when the order is placed.

Can you have a more thorough inspection beyond the standard non-invasive inspection? Yes, for an additional fee and with the permission of the property owner, we will unearth various parts of the septic system. Dye testing is available as well as testing of soils for fecal matter. Hydraulic Load TestsĀ are also available. Contact our office for pricing.

Owning your own septic system has advantages and disadvantages. Public systems, of course, have fees associated with their use; private systems avoid these fees but are not without operating cost. When a public system needs renovation, the cost often is divided among a large number of people. When a private system fails, it’s usually the owner’s problem alone.

If you are buying or selling a home, a septic inspection is a good investment. While a favorable inspection does not guarantee that you will not have trouble with the septic system, it can often detect defects that would go unnoticed to the untrained eye. It could save the buyer a major expense.

Why Choose Suburban Property Inspections?

If you are looking for an unbiased opinion and an experienced team of inspectors to do the best non-invasive inspection possible, then you are looking for Suburban Property Inspections.

No conflict of interest. Would you like to see your septic inspector arrive with a backhoe to do your inspection? Are they planning on a failure, and see dollar signs for the repair work? At SPI, all we do is inspect so there is no conflict of interest.

Experience. At SPI, our PSMA trained inspectors do literally hundreds of septic inspections each year and have been doing so since 1988. We are accustomed to the tricks some play to hide a system that is not working properly. We also are familiar with systems that are unusual or older in their configuration, even though they work just fine.

Additional Services. Suburban Property Inspections offers additional unbiased inspections and testing services, such as Home and Termite inspections and Water and Radon testing. Our knowledgeable office personnel are available to answer your questions and schedule your inspections.

Multi-service discounts available.