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About Septic Systems

Contents:

+ What is a Septic System?
+ Should I have the system inspected?
+ Care and feeding of your Septic Tank?
+ How often should I have my system pumped?

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What is a Septic System?

A septic system is a highly efficient, self-contained, underground wastewater treatment system. Because septic systems treat and dispose of household wastewater onsite, they are often more economical than centralized sewer systems in rural areas where lot sizes are larger and houses are spaced widely apart. Septic systems are also simple in design, which make them generally less expensive to install and maintain. And by using natural processes to treat the wastewater onsite, usually in a homeowner's backyard, septic systems don't require the installation of miles of sewer lines, making them less disruptive to the environment.

A septic system consists of two main parts: a septic tank and a drainfield. The septic tank is a watertight box, usually made of concrete or fiberglass, with an inlet and outlet pipe. Wastewater flows from the home to the septic tank through the sewer pipe. The septic tank treats the wastewater naturally by holding it in the tank long enough for solids and liquids to separate. The wastewater forms three layers inside the tank. Solids lighter than water (such as greases and oils) float to the top forming a layer of scum. Solids heavier than water settle at the bottom of the tank forming a layer of sludge. This leaves a middle layer of partially clarified wastewater.

Wastewater comes into the septic tank from the sewer pipes in the house, as shown here:

A septic tank naturally produces gases (caused by bacteria breaking down the organic material in the wastewater), and these gases don't smell good. Sinks therefore have loops of pipe called P-traps that hold water in the lower loop and block the gases from flowing back into the house. The gases flow up a vent pipe instead -- if you look at the roof of any house, you will see one or more vent pipes poking through.

As new water enters the tank, it displaces the water that's already there. This water flows out of the septic tank and into a drain field. A drain field is made of perforated pipes buried in trenches filled with gravel.

A typical drain field pipe is 4 inches (10 centimeters) in diameter and is buried in a trench that is 4 to 6 feet (about 1.5 m) deep and 2 feet (0.6 m) wide. The gravel fills the bottom 2 to 3 feet of the trench and dirt covers the gravel.

The water is slowly absorbed and filtered by the ground in the drain field. The size of the drain field is determined by how well the ground absorbs water. In places where the ground is hard clay that absorbs water very slowly, the drain field has to be much bigger. A septic system is normally powered by nothing but gravity. Water flows down from the house to the tank, and down from the tank to the drain field. It is a completely passive system.

You may have heard the expression, "The grass is always greener over the septic tank." Actually, it's the drain field, and the grass really is greener -- it takes advantage of the moisture and nutrients in the drain field.

Should I have the system inspected?

The purpose of an inspection is to evaluate the present and future performance of an existing onsite sewage treatment system. It is likely that an inspection cannot show the true present condition of all parts of the system. The inspection certificate might state that the onsite sewage treatment system has been inspected and found to be in "satisfactory working condition" and apparently not in violation of any local sanitary codes. The definition of "satisfactory working condition" must be clearly defined and understood by all concerned parties. The provisions of the local sanitary code must be thoroughly known by the inspector. The toilets may flush, all the drains may work with no back up, but the inside-the-house conditions say little about the condition of the onsite sewage treatment system. There may be no evidence of sewage surfacing in the area of the drainfield, but this doesn't mean that the drainfield is not full and at maximum capacity. A greater daily water use may cause a sewage back up or surfacing on the lawn.

The fact that the septic system appears to be in working condition at the present time is definitely not a warranty or guarantee that the system will continue to function properly for any given period of time in the future. This point must be carefully and fully explained to all interested parties. The average daily capacity of the system has been established by previous construction procedures and previous maintenance of the septic system. The average daily water use and future maintenance cannot be controlled by the person who inspects and issues a certificate of inspection of the system.

Inspection is for whom?

There are a number of parties vitally interested in the results of an inspection of the onsite sewage treatment system. They are the buyer, the seller, the real estate agent, the lending agency, and the local unit of government. They all have slightly different interests. The seller wants a clean bill of health for the sewage treatment system since "We never had a problem with it!" The prospective buyer wants the house but "Never wants to have a problem with the sewage system!" The lender wants the deal to go through as quickly and as smoothly as possible with no future problems. The real estate agent is interested in a commission as soon as possible. The local unit of government wants to know if the onsite system is up to the current standards and is not a public nuisance or health hazard. The inspector must prepare a report that will provide some answer to all the questions that might be raised.

An educational program about the operation of an onsite sewage treatment system along with inspection procedures and results is clearly needed. Some of the interested parties likely are not familiar with the operation and maintenance of an onsite sewage treatment system. The prospective owner certainly should be. And if the system doesn't work, that education will begin in a hurry.

"Bury it and forget it" is unfortunately too common a practice with onsite sewage treatment systems. The onsite professional should know that without frequent cleaning of the septic tank, solids will wash out of the tank into the drainfield. The amount of solids in the drainfield may range from negligible to nearly full. Certainly a drainfield with only a few solids will perform better and longer than a drainfield that is nearly full of solids. "The toilet still flushes good!" is a common evaluation of the onsite sewage treatment system. But, the prospective buyer wants to know for how long and the inspector is expected to provide that information.Can any drainfield handle any amount of waste water that may be discharged into it? Absolutely not! Every soil absorption system has a maximum capacity, which when exceeded will result in a probl em. Sewage will either back up in the basement or surface at the soil absorption unit. Which one happens depends on the relative elevation of the house and the drainfield.

What was the estimated water use of the present owners? What is the estimated water use of the prospective purchasers? What will happen to the system if the water use increases by double or more? Seller, buyer, lender, and agent had all better be well informed on what the amount of waste water means to the operation of an onsite sewage treatment system. It is the inspector's duty to clearly inform them, preferably in writing, so there is less chance of a misunderstanding.

Some questions that may need answers are:

• How thoroughly can the system be inspected without doing harm?
• What time of the year is the inspection being conducted?
• Has it been dry or has there been a prolonged wet spell?
• What would a new onsite sewage treatment system cost?
• Is there room on the lot for a new system?
• If the seller is sure that the present onsite system is adequate, would they be willing to put dollars in escrow as a guarantee?
• What will happen to the onsite system if the buyer moves in and uses extra large volumes of water?
• Could a water meter be installed for a period of time before the seller moves out?

The projected performance of the onsite system could be related to this water use. If the buyer is not willing to be restricted to such use, other provisions will need to be made.

As an example, let's say that two people have occupied the house now up for sale for 15 years. The onsite system is likely treating at least 150 gallons per day. The septic tank has been cleaned regularly and the present occupants have never had any sewage back up or surfacing. The buyers are a family of six &emdash; mom and dad, and four teenagers. The odds are very good that this family will use considerably more water than 150 gallons per day. Will the existing system handle more than 150 gallons per day? If so, how much more? How can one predict? If the system backs up or surfaces soon after the new family moves in, whose fault is it? Does the seller have the responsibility to provide an onsite system large enough for the water use of any buyer?

Serious questions that need to be answered to predict the capacity and life of an onsite sewage treatment system are:

1. How old is the onsite system? What month and year was it installed? (The month would tell something about possible soil moisture conditions and smearing during installation of the system.)
2. Is the sewage tank a septic tank or an aerobic tank? If aerobic, determine the name of the manufacturer.
3. What is the liquid volume of the septic tank?
4. How frequently have the solids been removed from the septic tank? What has been the cleaning schedule since the tank was new?
5. What type of tank cleaning procedure was used?
6. What was the average sewage flow in gallons per day?
   1. Water meter readings or;
   2. An estimate based on number and age of occupants, and number and type of water-using appliances
7. What is the construction and layout of the drainfield?
   1. Seepage pit or pits
   2. Seepage bed
   3. Sewage treatment mound
   4. Drainfield trenches with distribution box
   5. Drainfield trenches with drop boxes
8. Has the drainfield ever been repaired or added to?
9. What is the size of the drainfield; i.e., area of drainfield rock?
10. Are there inspection pipes to measure the liquid level in the drainfield or parts of the drainfield?
11. What is the liquid level in the drainfield?
12. How much of the drainfield has liquid ponded in it?
13. How much sludge from the septic tank has washed out of the septic tank into the drainfield?
14. What is the predicted average capacity of the drainfield to treat septic tank effluent, measured in gallons per day, for the next 10 years or longer?
15. What assurances can the inspector give that the answers are correct and the predictions of future performance accurate?
16. Does the inspector have liability insurance in the remote event that the predictions are incorrect or misinterpreted?

General information needed:

• Date that the system was installed; age of the system.
• Permit issued by local unit of government; get a copy.
• As-built plans available? Get a copy.
• How many people used the system; ages. (This is important for predicting water use.)
• Was a garbage disposal used? Is one installed in the house?
• Estimate the average daily sewage flow by the residents.
• Was the laundry done in town at the laundromat?
• Water using appliances; water softener; iron filter; automatic washer; dishwasher; whirlpool bath; spa; etc.
• Septic tank cleaning frequency?
• Who did it?
• Are they reputable and do a good job?
• Is the house currently occupied?
• Do all the toilets flush and all the drains work? What information does this give?

Care of your Septic Tank

Since the septic tank is such an essential part of a sewage system, here are some points to remember about the "care and feeding" of that part of the onsite sewage treatment system.

A "starter" is not needed for bacterial action to begin in a septic tank. Many bacteria are present in the materials deposited into the tank and will thrive under the growth conditions present.

If you feel that an additive is needed, be aware that some may do great harm. Additives that advertise to "eliminate" tank cleaning may cause the sludge layer to fluff up and be washed out into the drainfield, plugging soil pores. Some additives, particularly degreasers, may contain carcinogens (cancer-causing) or suspected carcinogens that will flow into the ground water along with the water from the soil treatment unit. Send all sewage into the septic tank. Don't run laundry wastes directly into the drainfield, since soap or detergent scum will plug the soil pores, causing failure. Normal amounts of household detergents, bleaches, drain cleaners, and other household chemicals can be used and won't stop the bacterial action in the septic tank. But don't use excessive amounts of any household chemicals. Do not dump cleaning water for latex paint brushes and cans into the house sewer.

Don't deposit coffee grounds, cooking fats, wet-strength towels, disposable diapers, facial tissues, cigarette butts, and other non-decomposable materials into the house sewer. These materials won't decompose and will fill the septic tank and plug the system. To use a 5-gallon toilet flush to get rid of a cigarette butt is also very wasteful of water. Keep an ash tray in the bathroom, if necessary.

Avoid dumping grease down the drain. It may plug sewer pipes or build up in the septic tank and plug the inlet. Keep a separate container for waste grease and throw it out with the garbage.

If you must use a garbage disposal, you will likely need to remove septic tank solids every year or more often. Ground garbage will likely find its way out of the septic tank and plug up the drainfield. It is better to compost, incinerate, or deposit the materials in the garbage that will be hauled away. As one ad says, "You can pay me now, or pay me later." Use a good quality toilet tissue that breaks up easily when wet. One way to find out is to put a hand full of toilet tissue in a fruit jar half full of water. Shake the jar and if the tissue breaks up easily, the product is suitable for the septic tank. High wet-strength tissues are not suitable. As long as the tissue breaks up easily, color has no effect on the septic tank. Many scented toilet tissues have high wet strength.

 

Clean your septic tank every one to three years. How often depends on the size of the tank and how many solids go into it. A rule of thumb is once every 3 years for a 1,000 gallon tank serving a 3-bedroom home with 4 occupants (and with no garbage disposal). Here is a word of caution: Never go down into a septic tank. The gases present may poison or asphyxiate you. Only trained professionals should enter a septic tank or any other confined space. To properly clean a septic tank, the manhole cover or the tank cover must be removed. This is the only way to be sure that all the solids have been pumped out. A septic tank cannot be cleaned adequately by pumping out liquids through a 4-inch inspection pipe. Doing so often results in some of the scum layer plugging the outlet baffle when the tank refills with sewage. Be sure that the tank is opened when it is cleaned. At this time the baffles should be inspected and replaced if necessary. Recharge wastes from a properly operating water softener will not harm septic tank action, but the additional water must be treated and disposed of by the drainfield. If the softener recharge overloads the sewage system, this waste water can be discharged to the ground surface since it contains no pathogens. But it must be discharged in a location where it will not be a nuisance or damage valuable grass or plants.

Using too much soap or detergent can cause problems with the septic system. It is difficult to estimate how dirty a load of laundry is, and most people use far more cleaning power than is needed. If there are lots of suds in your laundry tub when the washer discharges, cut back on the amount of detergent for the next similar load. It's generally best not to use inexpensive detergents which may contain excessive amounts of filler or carrier. Some of these fillers are montmorillonite clay, which is used to seal soils! The best solution may be to use a liquid laundry detergent, since they are less likely to have carriers or fillers that may harm the septic system.

Each septic system has a certain capacity. When this capacity is reached or exceeded, there will likely be problems because the system won't take as much sewage as you want to discharge into it. When the onsite sewage treatment system reaches its daily capacity, be conservative with your use of water. Each gallon of water that flows into the drain must go through the septic tank and into the soil absorption unit. Following are some ways to conserve water that should cause little hardship in anyone's standard of living:

Be sure that there are no leaking faucets or other plumbing fixtures. Routinely check the float valve on all toilets to be sure it isn't sticking and the water isn't running continuously. It doesn't take long for the water from a leaking toilet or a faucet to add up. A cup of water leaking out of a toilet every minute doesn't seem like much but that's 90 gallons a day! So be sure that there is no water flowing into the sewer when all water-using appliances are supposed to be off.

Installing a water meter is a sure way to know how much water you are using and how much the water use will be reduced by doing certain things. A water meter for a home should cost from $50 to $100 plus installation.

The most effective way to reduce the sewage flow from a house is to reduce the toilet wastes, which usually account for about 40 percent of the sewage flow. Many toilets use five to six gallons per flush. Some of the so-called low water use toilets are advertised to use only 3.5 gallons per flush. Usually the design of the bowl hasn't been changed, however, and often two flushes are needed to remove all solids. That's seven gallons! Toilets are available which have been redesigned and will do a good job with one gallon or less per flush. Using a one-gallon toilet rather than a five gallon toilet will reduce sewage flows from a home by about a third. This reduction may be more than enough to make the sewage system function again. While prices may vary, one-gallon toilets can usually be purchased in the $200 range, far less than the cost of a new sewage treatment system.

With a water meter you can determine how much water your automatic washer uses per cycle. Many washers now have settings to reduce the amount of water used for small loads. Front loading washers and suds savers use less water than top loading machines. If your sewage treatment system is reaching its maximum capacity, try to spread the washing out during the week to avoid overloading the sewage system on a single day. Baths and showers can use lots of water. "Setting up camp" in the shower with a shower head flow of 5 gallons per minute will require 100 gallons in 20 minutes. Shower heads that limit the flow to 1.5 or 2 gallons per minute are available and should be used. Filling the tub not quite so full and limiting the length of showers will result in appreciable water savings. Is the water from the faucet cold enough to drink? How long do you let it run to cool down? Keep a container of drinking water in the refrigerator. Then it won't be necessary to run water from your faucets in order to get a cool drink. There may be other ways to conserve water that you can think of in your home. The main idea is to consider water as a valuable resource and not to waste it.

Following a few simple rules like not using too much water and not depositing materials in the septic tank that bacteria can't decompose should help to make a septic system trouble-free for many years. But don't forget the septic tank does need to be cleaned out when too many solids build up. Septic tanks need tender, loving care, too

How often should I have my system pumped?

The frequency of pumping depends on several factors:
capacity of the septic tank
volume of wastewater
amount of solids in wastewater

The following table lists estimated pumping frequency according to septic tank capacity and household size. The frequencies were calculated to provide a minimum of 24 hours of wastewater retention assuming 50 percent digestion of the retained solids. These numbers are for estimation purposes only - every system and situation is different and pumping may be required more or less often than indicated. If you are in doubt, contact your local septic system professional.

Estimated septic tank pumping frequencies in years for full-time residences:

Household size (number of people)

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