SKETCH of a typical aerobic treatment unit tank, aerator, chamberHome Buyer's Basic Guide to Septic Systems
Easy Guide to Inspection & Testing When Buying a Home With a Septic Tank

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Advice for Home Buyers who are buying a property with a private septic system. In order to help buyers obtain Information that addresses these concerns. We have put together this guide to help in making informed decisions regarding the potential problems and costs associated with a property's septic system. This document gives a simple overview of the questions to ask and tests and inspections to order if you are buying a property with a septic system.

If you don't really want to know much about septic systems but you want to know how to inspect and test this costly and buried system when you're buying a property with a septic system, septic tank, septic fields, then read this document.

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Basic Advice on Buying a House with a Septic System

Illustration of a conventional septic system including tank, D-box, and distribution field.Frequently prospective buyers of a single family home have many questions regarding the septic system serving the dwelling:

If you prefer a complete, detailed guide to how to determine the condition of a septic tank, drainfield, leach field, soakaway bed, piping, etc. before buying or selling a home, see our buyer's guide to septic systems beginning at HOME BUYERS GUIDE to SEPTIC SYSTEMS.

If you need to know still more about septic system components, septic system maintenance (such as tank pumping and septic additives), or details about septic system inspection, diagnosis, repair, and alternative septic designs, Our main septic website page provides in-depth articles about these topics.

Components of a Septic System

In simplest terms, a septic system consists of a holding tank which retains solid waste and grease from household waste water, and an absorption system or "leach field" which disposes of liquid wastewater or "effluent" which leaves the septic tank for absorption below ground into soils at the property.

How to Inspect and Test a Septic System When Buying A Home

Why inspect and test a septic system before buying a home?

The septic system is a relatively expensive and buried system which does not have an infinite life. Eventually drain fields fail and sometimes septic tanks, especially steel ones, rust out and need replacement. Also, old septic tanks, cesspools, and drywells, especially site-built or "home made" systems and systems in certain soils, can collapse, forming a very dangerous site hazard.

While no septic inspection and test can guarantee 100% that all septic defects have been found, properly conducted, these procedures can reduce the chances of a dangerous or costly surprise at your new home.

Septic Inspection and Testing for Home Buyers, Step-by-Step

You can do steps 1 and 2 yourself. If you hire an expert to inspect and test the system (some home inspectors can provide this service), the inspector will also perform step 2 and 3.

  1. Basic Questions:Ask the seller the following questions. Don't worry if the seller says they don't know the answers. "Not knowing" is also important information. These questions are deliberately a bit vague in order to allow people to tell you whatever they know rather than cutting off or suggesting answers. Convey the answers to these questions to your septic test consultant.
    • How old is the property?
    • Is the property occupied or vacant? If occupied, for how long and by how many occupants? If vacant, for how long?
    • How long has the seller owned the property?
    • Where is the septic system?
    • What is installed?
    • What is the service or repair history of the septic system?
    • When was the tank last pumped? [Warning: if the seller offers to "have the tank pumped for you" ask them not to do you that favor before your inspection as pumping the tank prevents testing the drain field.]
  2. Visual Inspection: Make a visual inspection of the property. Look for wet areas, smelly areas, rocky areas, areas of recent excavation. Also make note of the location of and distance to nearby streams, private wells, ponds, buildings, property lines, and rocky areas, and areas of trees and shrubbery.

    [Warning: be very alert for evidence of sink holes or subsidence. Do not walk over anything suspicious as you might step into or fall into a collapsing system.]
  3. Septic Loading & Dye Test: Hire a septic test consultant to perform a septic loading and dye test. This procedure puts a test volume of water into the system to look for evidence of a blocked pipe or for breakout of septic effluent at the yard surface - indications of the need for repair. If you are looking at a completely new home and septic system you might omit this test but don't assume that new systems are immune to failures.

    Pipes settle and break or systems can be improperly installed. If the tank was pumped immediately before your inspection you should be suspicious, and you might defer the loading and dye test as it may be unable to put enough water into the system to test the drain fields. The dye itself is just a coloring agent to identify water that may appear at the yard surface. It's the test volume of water that's important.
  4. Pump and inspect the septic tank: this step may or may not be necessary, depending on the age and service history of the system and the results of the visual inspection and loading and dye test. Important additional information, available when the tank is pumped, can tell you if it was past-due for pumping (risking damaging the drain fields) and if it is damaged. You'll also know exactly where the tank is, if it's concrete, steel, fiberglass or home made, if it has been damaged, and if it has a save cover.

Additional steps which are not normally done but which may be performed if there is evidence of system damage or failure are listed next. These steps would ordinarily be performed by a septic contractor who installs or repairs septic systems. Some septic pumping companies also perform septic repairs and field investigations. A septic engineer may be needed if you are expanding a system or if you require design to repair a system on a difficult site.

More Reading about Septic System Inspection and Testing

More basic information about how septic systems work is in this document after this section. More in-depth information about the steps in the procedure outlined above can be read at the following online articles:

For a leaching system to function properly it must:

  1. Provide enough application area. The application area is the amount of surface area of soil within the leaching system where sewage effluent is applied (referred to as "wetted" area). The amount of application area needed for a given house depends on the characteristics of the soils on the property and the daily flows (in gallons) generated from the house.
  2. Be surrounded by natural soil conditions which will be able to dissipate and disperse the discharge without becoming over saturated.
  3. Provide enough capacity to store effluent during periods of unusually heavy use or when rainfall or subsurface flooding reduces the ability of the system to disperse the liquid. Note: Curtain drains or ground water interceptor drains are sometimes installed upgrade of the leaching system to minimize high ground water conditions.

It is important to realize that, once a septic system has been installed, only one of the above factors can be controlled by the homeowner. The homeowner can control how much water is actually being discharged to the system. Since each system has a set maximum capacity, it behooves the homeowner not to exceed that amount.

Signs of Trouble With the Septic System

If a system starts to experience difficulties, what are some of the common symptoms?

  1. Plumbing fixtures may exhibit difficulty in releasing their contents (slow draining, bubbling, backups, etc.). This condition may be system-related but it could also indicate just a clog in the interior piping or sewer line.

    You should have the interior piping checked before proceeding with an investigation of the sewage disposal system. [DJF added: See CLOGGED DRAIN DIAGNOSIS & REPAIR]
  2. Large volume discharges (such as, washing machines, dishwashers and bathtubs) cause either a backup, as noted above, or, an overflow of sewage above the septic tank or leaching field. If this condition is usually at its worst during and/or directly following a heavy rain event, then the septic system is indeed suspect.

    If backup alone occurs independent of wet weather, you might first check for a partial blockage of the main drain that has occurred some distance from the house. In such cases a small discharge will simply be held by the main waste pipe, draining slowly past the blockage, while a large discharge will cause a backup.
  3. Foul septic odors in storm drainage piping, catch basins, footing drain piping or curtain drain discharges may indicate that sewage from your property or an adjacent one is entering these ground water systems.

Sources of Information about your particular septic system

What can a prospective purchaser of a home do to gather as much information as possible relative to the present condition of a system and about possible future expenses associated with the septic system? Here are a few suggestions:

Obtain Information about the septic system from the present property owner

Make a Visual Site Inspection of Septic System Condition at the Property

Go to Town Health Department to Review the Property's Septic System Information File

Obtain Additional Information from Outside Sources

Home Buyers' Guide to Septic Systems - A Final Overview

It is our opinion that when buying a home, especially one that is old and does not have a sewage disposal system that meets today's standards, the fundamental questions that should be answered are:

  1. Is the septic system currently working properly or is there evidence of a failure?
  2. Even if it's working, are there signs suggesting short remaining life of the septic system?
  3. When the existing system fails, how will we repair it and how much will repairs cost?

If accurate soil test data is not available through the local health department the only sure way of answering the question is to actually perform all the deep hole testing and percolation tests required by code.

As you can understand, most sellers would take a dim view of prospective buyers wanting to tear up their property to perform then tests. Therefore the more information a buyer can obtain, the better able he or she will be able to judge the adequacy of the existing system and what will most likely be required to repair the system, when needed. In that way, the buyer will not be caught unaware when that day arrives, since it was part of the financial assessment establishing the value of the property at the time of purchase.

Key Septic Testing Articles


Continue reading at HOME BUYERS GUIDE to SEPTIC SYSTEMS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

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SEPTIC SYSTEM TEST BASICS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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