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Bulletin #7084, What to know About Septic Systems When You Buy or Sell a House

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Water Quality

What to know About Septic Systems When You Buy or Sell a House

Reviewed and updated by John M. Jemison, Jr., Extension water quality and soil specialist

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Decisions about purchasing a new home are based on the looks of the house, size, location and price, but not the septic system. Since the septic system is half of the home’s life support system, it warrants attention. Just imagine what would happen if you moved in, feeling financially strapped, then you discovered you needed to install a new septic system. Or you found a buyer, closed the deal and discovered the new owner was suing you because the septic system failed. This fact sheet lists major points to consider when you buy or sell a house. It is not a substitute for professional inspection, which is recommended. Use these tips in conjunction with Your Septic System, water quality bulletin #7080.

Function of the System

Since the septic system is usually not visible, it is easy to forget that it is a vital part of the home. The septic system accepts and treats waste water (sewage) from your house to prevent biological and/or nutrient pollutants from contaminating your well or nearby lakes and streams. When functioning properly, a septic system has an average life expectancy of 15 to 25 years.

Age of the System

The age of the house may indicate the condition and type of septic system. Houses built in Maine before 1974 may use the original waste disposal system. Some older houses may have had the original system replaced. Just because the system is over 10 years old does not mean you will need to replace it soon. If the tank has been pumped regularly and the drain field treated properly, the septic system may function for many years. As most homeowners learn, parts of the house wear out, so a replacement fund is a good idea.

Another way to determine the age of the septic system is to check a copy of the construction permit and the certificate of occupancy. They will indicate when the system was installed. If these documents are lost or misplaced, your town office or state Department of Health Engineering should have them on file and be able to give you copies. Check for any discrepancies between the location of the system and the placement in the sketch. When a considerable difference is found, an inadequate replacement system may have been installed without obtaining a permit.

If these forms are not available from the town, the system may be very old and need replacement. Wastes from the home may just be discharged into a dry well or cesspool, a roadside ditch or a  lake or stream; or the system may have been installed without the health department’s knowledge or approval. A site evaluator can evaluate your existing system and advise you on any necessary actions.

Size of the System

Septic systems in Maine usually are designed to adequately treat sewage based on 90 gallons per day per bedroom. This estimate assumes that two people will occupy each bedroom. Both buyer and seller benefit in knowing this.

Buyers need to know if the functioning system is large enough to adequately handle the new family’s wastes. A family of six moving into a two-bedroom house may soon overload the tank and eventually clog the absorption field. A potential homeowner who is aware of an undersized system can plan to expand or replace the system or buy a different house.

If the seller is aware of the size of the system, the real estate agent and the potential buyer should be informed. A buyer cannot sue after the sale on the basis of a defective system if he or she has been informed that the system is not adequate for the new family.

Evaluating the System

A well and septic system evaluation should be conducted as soon as the property is placed on the market so that any necessary repairs can be made. The evaluation definitely needs to be done before the sale is completed.

At a minimum, an evaluation should include:

  • The location, age, size and original design of both the water and septic systems. The type of septic tank: concrete, plastic or steel. The accuracy and availability of the construction permit and the certificate of occupancy.
  • The soil conditions, drainage, seasonal high water table level and flooding possibilities where the system is.
  • The condition of the plumbing fixtures and their layout, which determine whether structural changes have been made to the plumbing to increase flow to the septic system above capacity. Identify system components that could affect the system—water softeners draining to the septic tank or footing drains.
  • The date that the septic tank was last pumped and a record of previous pumping.
  • The sludge (solid material) level in the septic tank (if it has not been recently pumped) and baffle conditions.
  • The state of the absorption field. Look for evidence of waste water reaching the soil surface, soggy areas and/or standing water. The possibility of biological contaminants in the water.

Since considerable skill is needed to evaluate well water quality and a septic system, the inspection should be done by a professional engineer, building inspector, or septic system inspector. There will be a charge for this service, but it is worth the expense if it avoids lawsuits or a lost sale.

Even a professional inspection may fail to identify septic system deficiencies or problems if the house is vacant during inspection. As buyer, make certain the evaluation is done when the system is being used normally for 30 to 60 days. If the house is vacant, or the seller’s family was small, the buyer may want to negotiate that final acceptance of the house is conditional upon 30 to 60 days of normal use.


A Checklist*

  1. Find and mark the location of the well and septic system. (You may want to map this information in the space provided in Your Septic System, water quality bulletin #7080.)
  2. When was the septic tank last pumped? ___________________
  3. Is there any standing water, soggy ground or smelly liquid near the absorption field? __YES  __NO
  4. Are there any areas over the drain field that appear highly compacted (i.e., roads or evidence of continued vehicle travel)? __YES  __NO
  5. Have any major additions been made to the house since the present septic system was installed? __YES  __NO
  6. Does the ground slope toward the septic tank or absorption field? __YES  __NO
  7. Do neighbors have frequent problems with their systems or have they noticed problems with this one? __YES  __NO
  8. Does the grass over the drain field appear much greener than the surrounding area, even during dry weather? __YES  __NO
  9. Do toilets flush slowly? Does water drain slowly from sinks and tubs? Do either “gurgle?” __YES  __NO
  10. Does a water test indicate biological contamination of the well water? __YES  __NO
  11. Is the septic system (tank and absorption field) less than 100 feet from the well or 100 feet from a lake, stream or pond, or not meet local codes, which may be stricter? __YES  __NO

If you answered YES to any question, the system may not be functioning properly. Consult a health department representative or professional for help.

*This checklist will help you make some preliminary judgments about the system you are evaluating. However, it is not as good as an on-site professional evaluation.

For more information on this subject, contact your Cooperative Extension county office.

Adapted from “Maintaining Your Septic System,” a set of Cornell Cooperative Extension fact sheets. Original authors include D. Solomon, E. Dersch, J. Saumier, A. Meyer, M. Keith, J. Saumier, and M. Shortlidge.


Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 2002, 2010

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