Septic tank schematic (C) Carson Dunlop Associates Complete Home Buyer's Guide to Septic Systems
Instructions for Buying a Home With a Septic Tank

  • HOME BUYERS GUIDE to SEPTIC SYSTEMS - home - CONTENTS: what a home buyer needs to know about buying a home with a septic tank & leachfield, how to maintain the septic system, what goes wrong with septic systems, & how to diagnos & repair septic system & drain line failures or backups.
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How to check out the septic system when buying a home.

This article series answers just about any question you might have about buying or owning a house with a septic system. The article gives critical advice to people buying a home with a septic tank and drainfield or similar septic systems.

We explain what a septic system is, we identify its basic parts, and we explain the basics of how private or onsite septic systems work.

This home buyer's guide to septic systems tells what inspection, testing, and maintenance are recommended when buying a home with a private septic system.Here we explain how to reduce the risk of a costly surprise by asking questions, visually inspecting the septic system, and by testing the septic system before buying a home. The drawing of a conventional two-compartment septic tank at page top and discussed in this article was provided courtesy of Carson Dunlop Associates.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

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Advice for People Buying a Home with a Septic Tank

Illustration of a conventional septic system including tank, D-box, and distribution field.

Article Contents

The articles in this series explain what a septic system is and outline step by step septic inspection and testing for home buyers. Learning a little about how septic systems work (described here) and about septic cleaning (removing septic waste), and testing a septic system before buying a new home can help you avoid installing a septic system or replacing the septic system as a big surprise.

Because the septic tank and drainfield at a property are buried, thus hidden from view, because these components are expensive to replace, and because a costly problem can be present but not obvious, it is important to understand the septic system and to inspect and test it when buying a property served by its own private septic tank.

Septic systems include buried septic tanks (sewage tanks) and drainfields - expensive and hidden from view such as in the photo at left. This document provides advice for home buyers who are buying a home with a private septic system: homes using a septic tank and drainfield or similar soil absorption system.

Other chapters of this guide explain what goes wrong with septic systems, 5-recommends and describes septic inspection and test methods in more detail, explains how to be sure your septic inspection and septic test are conducted properly, tells you where to get more septic system information about a given property, and warns of unsanitary or dangerous site conditions.

If you need to know how to install a septic system, or if you find that you have a sewage pit (cesspool) this website provides articles explaining those topics too. If you prefer to read a basic guide to septic system inspection and testing for home buyers all in one brief article,

Our schematic of a conventional two-compartment septic tank (below) illustrates the first of two major septic system parts: the septic treatment tank. The image is provided courtesy of Carson Dunlop Associates.

What is a Septic Tank and How do Septic Systems Work: Nine Basic Questions & Answers

Septic tank schematic (C) Carson Dunlop AssociatesHome buyers frequently ask us these questions about septic systems:

  1. "What is a Septic Tank?
  2. What is a Leach Field?
  3. How does a septic system work?
  4. What does the existing septic system consist of at my new home?
  5. Do I have a Cesspool or Drywell?
  6. How do I know if the septic system is working properly?
  7. What septic inspections and tests should I have performed when I am buying a home?
  8. How long will a septic system last?
  9. Is septic system maintenance necessary?"

To help buyers obtain the necessary information to address these questions, we have put together this document to guide them in making informed decisions regarding the potential problems and costs associated with a property's septic system.

What You Need to Know, Find-out, & Do when buying a home with a septic system

How Septic Systems Work. Here is the minimum you need to know and what you need to do (or have done) when buying a property with a septic system

Our sketch below shows the second major portion of a septic system: the effluent disposal or drainfield or soakaway bed that disposes of clarified effluent liquid waste that leaves the septic tank.

Illustration of a conventional septic system drain field

So how does a septic system work? A private onsite septic system means that the waste from your building drains (sinks, showers, toilets) goes into a septic tank which retains the solids and lets the effluent flow into the soils on the property.

To avoid contaminating the environment, including nearby wells and waterways, septic system wastewater must be treated to reduce its pathogenicity. Luckily naturally-occurring bacteria found in the septic tank and drainfield soils accomplish this task - as long as the septic system is working properly.

In a standard septic tank and drainfield system, about 40% of the treatment of sewage wastewater occurs in the septic tank, and the remaining 60% occurs in the drainfield trenches and surrounding soils.

Properly designed and installed private septic tank and drainfield or soakaway bed systems are functional and sanitary. Private septic systems serve more homes in the U.S. and many other countries than any other waste disposal method. But the components are costly and do not have an indefinite life.

Below in more detail we provide a LIST of the MAJOR COMPONENTSof Residential Septic Systems: Septic Tank, Drainfield, & a Description of How Septic Systems Work

Steps to Take When Buying a Home With a Septic Tank

Because of the potential repair/replacement costs involved, and because the system is buried and cannot be exhaustively inspected and tested, you want to do what you can to evaluate the condition of the septic system before you complete the purchase of the property.

Here's what to do: If you are buying a home with a septic tank and drain field, here's what you need to do, as succinctly as possible. Each of these steps is described in more detail below, and in even more detail in linked-to documents.

Steps 1 and 2 are essential. Step 3 is usually a good idea. Step 4 depends on the results of steps 1,2,3 but is usually a good idea. Step 5 is not usually done but might be necessary. Step 6 is what you do if you're being really thorough.

Synonyms for "septic system" used by the general public include septic waste system, sewage systems, and water sewage systems, even Roman sewage systems. All of these refer to onsite systems which hold and separate sewage waste from its liquid effluent which is treated further and then disposed-of by any of a variety of means which we will discuss.

At this site we also discuss special considerations for handling septic waste such as garbage disposal septic tank waste volume and what to do about it. Perform these steps in the order we list them. (For example, don't pump the tank before a loading and dye test.)

See HOME BUYER'S SEPTIC TEST for more details about steps 1, 2, 3 in this list.

  1. Ask About the Septic System - where is it, what's installed, what's the service and repair history. If the owners don't know where the septic system is, ask how long they've lived in the home: that will be informative.
  2. Make a Visual Site Inspection for signs of trouble. Here's a great clue: if nobody knows where the septic tank is, then you can be sure nobody has been maintaining the septic system as regular pumpouts are an important part of septic system maintenance and septic system life preservation.

    To find the septic tank see SEPTIC TANK, HOW TO FIND. If you can find the tank, for safety, be sure that there is no evidence of collapse or subsidence on the property, and be sure that the septic tank (or cesspool, or drywell) has a safe cover so that no one can fall into the tank.

    See SEPTIC TANK COVERS for details.
  3. Perform a Septic Loading & Dye Test to see if it produces evidence of a failure. Hire a home inspector who knows how to perform and will include this test.
    and also
    See SEPTIC DYE TEST WARNINGS for warnings about what can go wrong during septic testing or what can give false test results.

    Or SEPTIC SYSTEM INSPECTION & TEST GUIDE for complete details of how a septic system test is performed.
  4. Pump the Septic Tank and inspect for additional clues, depending on what you learned at 1,2,3. Abnormal sewage levels in the septic tank can be a strong indicator of a problem with the septic system.

    See SEPTIC TANK PUMPOUT TIMING ERRORS for pumpout timing details

    Watch out: don't pump a septic tank before the septic test: doing so will prevent a valid septic loading & dye test.

    At SEPTIC TANK LEVELS of SEWAGE we explain how to interpret the meaning of high or low sewage levels in the septic tank as well as thick or thin scum or sludge levels. For general septic tank maintenance

  5. Additional Septic System Physical Investigation might be needed if during the visual site inspection, the septic loading and dye test, or the septic tank open inspection and pumpout disclose abnormal conditions.
  6. Get Outside Information about the septic system: There are some independnt sources of information about the septic system at your property that you can check in order to be thorough.
  7. Check neighboring properties and their nearby septic systems both for advice for dealing with a neighboring septic system producing odors or seepage and to look for encroachment onto the property you are buying

The six home buying steps listed above are explained in detail at HOME BUYER'S SEPTIC TEST but first you might want to review the basics about septic systems at
and also
with septic systems.

Conflicts of Interest at Septic System Inspections & Home Inspections

Watch out for conflicts of interest when hiring a home inspector or a septic system inspector to examine a property before purchase. Choose an inspector who is qualified, experienced, and who will protect your interest.

Because sale of homes is a low volume high stakes deal, everyone involved feels a lot of pressure. That pressure explains why a home seller and real estate agents are very nervous about any inspector who they thinks may "rock the boat" and jeopardize their sale, though that's no excuse for putting the new home owner and occupants at risk of financial injury or worse, personal injury.

Real estate is very much a "caveat-emptor" buyer beware transaction, and the buyer is expected to perform her own due diligence. In fact, in our OPINION some of the pertinent real estate laws, while reasonable on the face of it, such as excusing an agent from liability regarding any representation of property condition, may at times encourage ... well how should we put it ... not the most honest behavior.

The concerns felt by the real estate profession may have contributed to the recent elimination of the NYS Home Inspection Advisory Board who tried monitored and advised on legislation regulating home inspectors in New York State. That news, reported by NYSAHI[5], was a sad step in a bad direction.

But more encouraging, in April 2012, the Code of Ethics for Home Inspectors for the State of New York, Title 19 NYCRR[3], now includes this text:

197-4.7 Conflicts of Interest

e) Home inspectors shall not directly or indirectly compensate, in any way, real estate brokers, real estate salespersons, real estate brokerage companies, lending institutions or any other party or parties that expect to have a financial interest in closing the transaction, for future referrals of inspections or for inclusion on a list of recommended inspectors or preferred providers or any similar arrangement.

That provision means that inspectors can't pay realtors for referrals. The fly in the ointment of that salve is that nothing prevents a realtor from "steering" a home buyer to inspectors whom the agent knows will soft-soap or under-report concerns at a property. All it takes is a list or a wink and a nod when naming names.

That is why we have long held that folks buying a home should obtain inspection services from experts who have absolutely no relationship with others in the transaction and who are referred by independent sources such as professional home inspector associations[4] or friends or neighbors.  In our OPINION real estate agents and even lawyers for whom real estate closings are a significant part of their business should only refer their clients to independently-maintained lists of inspectors and never to their own lists or friends.

The New York State Association of Home Inspectors (NYSAHI) considers placement by a realtor (or attorney) on a list of "preferred providers" constitutes a referral, as do oral or un-written referrals as well.

Conflicts of interest are not just unethical, they invite a lawsuit for fraud.

Watch out: septic system inspections are not included in typical state home inspector regulations and laws, even if the inspector was also performing a home inspection at the time. In essence, as of 2012, ancillary property inspection and testing services such as septic inspection and testing and environmental inspections and testing are not covered by home inspection regulations.

A home inspector or a septic system inspector cannot tell you whether or not you should buy a property. But s/he is expected to tell you about conditions that are dangerous, things that need near-term expensive repair or replacement (like a septic tank or drainfield if that inspection is performed), and about things you need that just don't work at an acceptable level of safety and reliability. An inspector who skips those items didn't do such a great job.

It would be unusual for the cost of repairs to be such a big portion of purchase price that a buyer should not proceed with the purchase. But a buyer needs to know what repairs are needed now and in the near future, what condtions are unsafe, and what conditions are causing rapid costly damage to the property - that's how the buyer can make a financially responsible financial plan, know how much money is needed, and know the priority of how to spend repair dollars.

Perhaps if enough cases of deception, manipulation, soft-soaping, or ms-representation by inspectors who are plagued by conflicts of interest reach the courts, those who are not moved by ethics will be moved by the law, and by the cost of failing to protect their putative clients.

List of Major the Major Components of Residential Septic Systems: Septic Tank, Drainfield, & More

SEPTIC SYSTEM COMPONENTS - the Basic Parts of a Conventional Septic Tank and Leachfield

Our sketch of a typical septic tank and drainfield (below) illustrates how waste moves from the building to the septic tank and how liquid waste is ultimately treated and disposed-of in the leachfield or drainfield.

Top View Sketch of Septic Septic System Components

The purpose of a septic system is to retain solid waste in the tank and to dispose of effluent waste water into the ground without contaminating the environment.

To accomplish this a septic system consists of the elements shown in the sketch above. 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.

Let's just outline these main septic system parts in a little more detail:

  1. The main waste line or "sewer line" connects the home's plumbing to the septic tank.
  2. The septic tank which is often buried just a few feet from the house foundation wall, receives all waste (solid and liquid) and has the main job of retaining solids and grease. Solids settle to the bottom of the tank as sludge. A floating scum and grease layer forms at the top of the tank.

    Baffles at the tank inlet and outlet reduce the velocity of liquid moving through the tank and prevent solids and floating scum from leaving.

    Clarified effluent is allowed to flow out of the tank into a soil absorption system. In some states (Connecticut since January 1991) septic tanks now consist of two compartments in order to do a more effective job, and increasingly other jurisdictions (Alaska, Pennsylvania) require that new and up-graded onsite wastewater disposal systems use two-compartment septic tanks.
  3. A effluent distribution pipe direct the flow of effluent from the septic tank to the leaching system, often connecting first to one or more distribution boxes which in turn distribute flow of effluent evenly into the leaching system.
  4. A leaching system, or soil absorption system, also called "drainfield", a soakaway system, leachfield, or seepage bed disperses the sewage effluent into the surrounding natural soils. There are many types of leaching systems but the most common is a network of perforated pipes buried in gravel-filled trenches. The specific type utilized on a particular property depends on the soil conditions and the amount of space available.

    Galleries or "septic galleys", seepage pits and sand beds have historically been used.

    Most distribution piping and leaching systems are "gravity" systems, meaning the flow runs through piping and distribution boxes without the assistance of any mechanical device, such as a pump or siphon, but some homes pump their effluent uphill into a mound system.

    Advanced wastewater treatment systems are also available to handle difficult sites.


Continue reading at HOME BUYER'S SEPTIC TEST or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.



Or see HOME SELLERS GUIDE TO SEPTIC INSPECT - what advice do we give to sellers of a home with a private septic system?


Or see these

Home Buyers & Home Owenrs Septic System Care Articles

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