LARGER VIEW of septic dye breakout at a basement entry from a failed septic system buried below a driveway during conduct of a septic loading and dye test
- an expert can find clues and perform tests that reduce risk of a costly surpriseWhat to Ask & How to Test a Home With a Septic Tank

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Guide to buying a property with a septic tank:

This document provides detailed step by step inspection and testing advice for home buyers who are buying a property with a private septic system, that is, a septic tank and a leach field or drainfield or similar soil absorption system.

We list detailed questions to ask about the septic system, how to perform the visual septic inspection, ordering the loading and septic dye test (the too-obvious results of a dye test at a problem site are in the photo at left), pumping the septic tank, and finding additional information about the septic system.

We explain how to be sure your septic inspection and septic test are conducted properly. We tell you where to get more septic system information about a given property, and we warn of unsanitary or dangerous site conditions.

Green links show where you are. © Copyright 2017, All Rights Reserved.

When, Where, Why, and How to Inspect and Test a Septic System When Buying a Home

While no septic inspection and test can guarantee 100% that all septic defects have been found, properly conducted, septic inspection and testing procedures can reduce the chances of a dangerous or costly surprise at a property served by an onsite waste disposal system.

When buying a home with a private septic system, septic tank and leachfield, at a minimum you should always should do steps

Some home inspectors can provide this service as can independent septic engineers and a few septic contractors. Below we tell you how to get the inspection and testing done properly. Other articles at this website give great detail about how to perform an effective and valid septic system inspection and test.

In case you missed it before, 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. Below we discuss each of these steps in more detail.

5-1. ASK ABOUT THE SYSTEM What to Ask the Property Owners About the Septic System

Basic Questions: (An essential step) 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.>

Other useful but less reliable sources of information about your septic system include:

5-2. VISUAL INSPECTION: Make a Visual Site Inspection for Signs of Septic Trouble or Site Limitations

LARGER VIEW yard with a wet area, digging begun by new home owner.

Visual Inspection of the septic system & the property: (An essential step) 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.]

Once the locations of the septic tank and leaching fields are known, walk over the entire area and observe whether there is any evidence of a sewage overflow condition. Greener grass in the leaching area may not necessarily indicate a system problem. If, however the area is completely saturated and odorous you should be very concerned. It most likely indicates an active failure.

Try to get a sense of how natural conditions are effecting the capacity of the property to disperse water.

All of the above factors could indicate that the existing system will experience difficulty or, that there may not be much additional area suitable for sewage disposal on the lot if needed in the future.

More Reading:
Table of Required Septic Clearances: Distances Between Septic System & Wells, Streams, Trees, etc.

Table of Required Well Clearances: Distances Between Drinking Water Wells and Septic Systems, Treated Soils, Farm buildings, & Other Site Features

5-3. LOADING & DYE TEST How to Perform a Home Buyer's Septic Loading & Dye Test

LARGER VIEW septic dye leaking at a main house drain wye.

This document section is maintained in a separate web page 5-3. LOADING & DYE TEST.

Text is repeated below for people who scroll down instead of using the left-side links to navigate the HOME BUYERs GUIDE to Septic Systems.

Most home sales are contingent upon a home Inspection. But home inspections do not usually include a test of the existing septic system. Septic Tests are beyond the scope of a professional home inspection but these septic tests are offered as an additional for-fee service by many home inspectors who serve areas where private systems are common. The photo at above left shows septic dye leaking out of a main house drain just after it was flushed down a toilet above.

Hire your own septic test consultant who has experience with and is familiar with septic loading and dye testing standards, a licensed septic inspector (in states which license this specialty such as MA), or a licensed septic system installer, who performs a great deal of work in the particular town. They can give you advise as to the condition of the soils and septic systems In the area and what might be expected (especially pertaining to costs) if/when you find problems with the existing system.

This photo shows a small property bordering on a river. We were told that a "new septic system" was installed but I could not see where a conventional tank and drainfield could possibly fit except below the driveway.

Because of the nearly overwhelming temptation at such sites to pipe septic effluent directly into the river, we performed a septic loading and dye test to see if the river would turn red. The river did not quickly turn red but after less than 100 gallons of water had been run into the septic system our red septic dye appeared at the basement entry platform at the edge of the driveway, as shown in the photo used at the top of this page.

Warning:: Unfortunately many of the people performing these tests perform only a perfunctory test such as a low-water volume test (50 gallons is meaningless) or use an insufficient amount of tracer septic dye. Therefore, the conclusions reached from these tests are often misleading. Be sure your test is performed by an expert and that an adequate volume of water is used. We specify no less than 50 gallons per bedroom or 250 gallons, whichever is greater.

Warning: if you hire a separate consultant to just perform the septic inspection and dye test you're at risk of getting a bad deal. It takes time to get enough water into the system to perform a reasonably aggressive test. It's economical to do this test if overlapped with other work at the site (like a home inspection). But someone coming to the site just to do the septic test is not going to wait around for 2+ hours for water to run into the system - you're likely to get an inadequate test. If you must use a third party just for this test be sure to review the test parameters and agree on them ahead of time.

Warning: Do not pump the septic tank before the loading and dye test. Depending on its size an empty septic tank could require 2-3 days' worth of water to re-fill the tank. An empty tank means that the "loading water" run into the system during the dye test procedure is simply filling the tank rather than testing the ability of the drain field to absorb effluent.

5-3a What is a Septic 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.

If the dye appears on the ground or appears in a brook or catch basin the system is in failure. We have seen dye breakout in 15-30 minutes in many instances where there was no pre-existing wet spot but where subsequent excavation confirmed that the system was either damaged or in failure.

More Reading:

SEPTIC LOADING & DYE TEST PROCEDURE, complete details of the septic loading and dye test procedure, test data forms, septic loading test water volumes, septic tracer dye quantities, critical observations.

5-3b TEST LIMITATIONS Septic Dye Test Limitations

Warning: if dyed effluent or water does not break out on the property surface, this does not necessarily mean the system is functioning or will function properly in the future. There are certainly cases in which effluent does not appear at the surface for some time, possibly up to five days, and there are other defects which predict upcoming expensive repair or replacement of the system but which are not detected by loading the drain field.

National data collected among professional home inspectors between 1985 and 1995 indicated that a significant number of inspectors performing dye tests discovered total failure of the septic system within 20 to 30 minutes of beginning testing.

We agree that a dye test is by no means a complete test of a system, that the other measures suggested here are extremely valuable, and that the volume of water used is critical: too little or too much can both be serious mistakes.

If a wet area or soggy area is present, dye has been found to appear in the short time indicated. However beware: NYS DEC has found dye appearing in nearby streams as late as five days following a septic dye test in cases where effluent migrates through considerable ground area before entering a stream.

5-3c FLOODING TESTS What Are Septic "Flooding Tests"?

Some authors describe an attempt to "flood" the septic system with 1000 gallons of water to attempt to force a sign of system failure to manifest itself. A typical home with a private well and pressure tank should be able to deliver 5 gallons per minute. If this test were performed overlapped with a home inspection (a 2 1/2 to 4 hour procedure) one could obtain this test volume.

Warning this test should not normally be attempted. Placing 1000 gallons of water into a septic system in two hours is likely to exceed its design parameters, and in the case of certain systems, it could actually damage the system. While all inspections and tests should aggressively seek to protect the interests of the parties involved by being thorough, a test which exceeds system design parameters would be improper.

5-3d PROBE TESTS of Septic Fields & Locating Septic Components

Probing is a procedure whereby the Inspector attempts to locate the "key" elements of the system (septic tanks and leach fields) and determine if they are experiencing hydraulic distress (meaning the septic tank and fields are flooded).

If a probe in a leach field produces a hole which fills rapidly with water this test indeed indicates a problem with the system. But if a probe does not produce this condition, the test has been unreliable since it may be during a time of dry soils or a day when very little water was used by the homeowner or the home in fact may have been vacant. This test, if performed, must be done by an expert, with caution, and is inconclusive if it does not detect a problem.

WARNING: probing can damage buried equipment such as fiberglass septic tanks or tank covers or plastic septic drain lines. Further, there is little assurance that the probing is done in the area where a problem is present.

More Reading:

5-4. PUMP THE TANK When and How to Pump the Septic Tank When Buying a Home

LARGER VIEW septic tank pumping contractor
pumping a tank.

After performing the septic loading and dye test and obtaining whatever historical maintenance and repair information you can obtain from the prior owner, you may want a septic contractor to located, open, pump, and inspect the septic tank.

The decision to include this next and more invasive step depends on what you have already learned about the age, history, and probable condition of the system. The pumping decision should be advised by the visual inspection, site history, and loading/dye test results.

Warning: [Repeated from the Dye Test discussion] Do not pump the septic tank before the loading and dye test. Depending on its size an empty septic tank could require 2-3 days' worth of water to re-fill the tank. An empty tank means that the "loading water" run into the system during the dye test procedure is simply filling the tank rather than testing the ability of the drain field to absorb effluent.

Pumping a septic tank prior to purchasing a home 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. For example, if a tank is less than two years old or was pumped in the last year, and if there are no other signs of septic problems at the site, we might defer the pumpout. In this case we would strongly recommend calling the pumper to ask about the condition of the system at the time they last cleaned it.

But pumping the tank for diagnostic reasons can be helpful in any case. 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, if the baffles are broken, if the tank has been flooded (indicating a blocked drainfield), and if the tank has a safe cover.

Even if there are no signs of trouble from the inspection and dye test, if nothing is known about the system history, or if it is known that the system has not been opened and pumped in 3 years or longer, this step is strongly advised. If the septic tank has been pumped quite recently, you should call the pumping contractor to ask if, at the time of pumping, the contractor observed any indications of system problems or upcoming system repairs.

5-5. ADDED INVESTIGATIONS Additional Septic System Physical Investigation Measures

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.

5-6. ASK OUTSIDERS Other Information Sources About Septic Systems

  1. Talk to neighbors about the general performance of septic systems In the area and specifically the system on the property you're Interested In. However, this is suggested only for those comfortable approaching this subject with strangers and with the realization that the information gathered may not be totally factual for various reasons (devaluation of their own property; not wanting to spoil the sale of a friendly neighbor, etc.)
  2. Soil Maps: Use of Soil Conservation Service County Soil Maps (through the town sanitarian), try to identify the type of soil most likely present on the site in order to predict the feasibility of future repairs to the existing leaching system.
  3. Water Meter Readings: Obtain water meter readings (if the home is serviced by a municipal water supply) to determine what the present occupants of the home are utilizing. Then compare those results with what your family is presently using. If your family Is using significantly more water than the former occupants you may be asking for trouble if the sewage system is undersized by today's standards.
  4. Septic Tank Pumper Records: Additional useful information which may be available from the service company who has pumped the tank recently includes the following:
    • Type of tank material - old steel tank may be at or end useful life
    • Tank size - along with usage determines appropriate pumping frequency and system capacity
    • Evidence of damage to tank components - broken baffles mean the leach fields are probably ruined
    • Evidence of backflow into the tank during start of pumping - indicates flooded leach field, probably failed
    • High sludge level and/or excessive floating scum level - indicate high risk of having pushed solids out into the leach field, destroying it

If the system has not been cleaned in several years and if the seller will permit, have the tank pumped to obtain this additional information. Typical pumpout fees are around $100. if excavation is not necessary. If the tank location is unknown extra costs will be involved to locate and excavate it - steps to which a seller is likely to object.

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

Septic Inspection & Testing Articles


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