Warnings When Performing a Septic Loading & Dye Test InspectAPedia® -
Warnings to inspectors and others who perform septic tests
What can go wrong with a septic loading & dye test?
How to perform a septic loading & dye test, step by step
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This chapter provides warnings and pitfalls facing people performing a Septic Loading and Dye Test. Although this test can often find a costly failure
it does not find all possible problems. So by itself a dye test is not indicative of complete condition of the system.
On the other hand, I've found so many failed systems with
this procedure that it's well worth performing.
Also see The Septic Information Website -
and see Septic Systems Inspection, Testing, & Maintenance online book on inspecting and maintaining septic systems,
of which the document is a chapter.
Technical review by industry experts has been performed and is ongoing - reviewers are listed at "References."
Comments and suggestions for content are welcome.
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Weak Septic Dye or Inadequate Amount: Some septic dye tablets, such as "Trace-A-Leak Tablets" may have
limited capacity.
These tablets are used by some inspectors for septic loading & dye tests.
However it is unlikely that they are a reliable indicator of surface
breakout or seepage.
While individual tablets will dissolve in 1-3 minutes,
they produce a yellow-green dye which may be difficult to see in grassy
areas. Worse, individual tablets produce dye in concentrations of
1 ppm/50 gallons of water. In order to stain a 1000-gallon septic
tank to produce visible output in the fields, at least 200 such tablets
would be required. Tablets are packaged in bottles of 100. A few
tablets, therefore, would in my opinion produce an unreliable test.
Beware of Bleach: we've encountered a number of instances in which the seller or real estate agent
was attempting to assure a satisfactory water coliform test by shocking the well just before a home inspection - in some
cases just minutes before arrival of the inspector.
Not only is such an act likely to be a commission of actionable
fraud, but it may do more than "hide" a well sanitation issue. If a large amount of bleach has been placed into the
septic tank it is possible for dye entering the system to be bleached colorless. If there is ready access to the
septic tank entry port, observe the septic dye entering the tank and confirm that it's not becoming colorless
at the instant of entry there.
A simple HACH test can also check for the presence of bleach in the
water supply or in suspected bleached-effluent.
This problem is discussed in more detail at Testing Water for Real Estate Transactions - Water Test Cheating Warnings for Home Buyers and Home Inspectors.
Four grams of 12% bleach will remove the coloration of one gram of septic dye in solution according to Tramfloc Inc.
Flush the toilet once BEFORE you put in the dye: this dye stains carpeting
and hands; if you put in the dye and the toilet overflows rather than draining
it's a terrible mess.
Certification: WARNING: in some jurisdictions, there are existing septic system inspection
procedures and in some cases inspector training/certification are required.
In some jurisdictions the inspection procedure does *NOT* include the
introduction of dye nor system loading with extra water volume.
Cesspools can obscure or prevent effective septic loading and dye testing::
If a cesspool is in use at a property a septic dye test would not be a reliable indication of good system condition
since the test could simply be trying to fill a large near-empty hole in the ground;
yet such a system may fail soon after being returned to active or heavier regular use.
Cesspool SAFETY WARNING: watch out for cave-ins, keep away: cesspools, particularly older site-built
cesspools present a very high risk of collapse from an unsafe cover or following some types of service involving
pumping, aeration, or hydro-jetting. Adults or children should not walk over or even near cesspools because of
the risk of falling-in followed by collapse, a virtually certain cause of death. If the presence of a cesspool
is known or suspected at a property its location should be roped off to prevent access and it should be investigated by a professional.
Drywells can obscure or prevent effective septic loading and dye testing: If a drywell system is installed, running water at the fixtures draining into this system
(as may be done by some septic tests) are likely to fail to perform a loading test on the septic system even if such a test was attempted.
First, the fixtures where water was run in attempt to test the septic system (tank and leach field) may not even be delivering
water to those components if instead the fixtures drain to a separate drywell. It is critical to trace building drains as part of
a septic test or to otherwise try to determine if the test water is actually entering the septic system.
Failed Septic System - Additional Warnings:
The onsite waste disposal system at a property with a failing or failed system is unsanitary and risks contamination of local ground water or wells.
According to the United States Environmental Protection Agency, failed septic systems are the most frequently reported cause of groundwater contamination.
Once a septic system stops treating the raw sewage it not only begins to contaminate the groundwater supplies, it also begins to contaminate
the surrounding soil as well.
High groundwater or deep septic effluent release:
Systems which release septage effluent at deeper levels in the soil (below 24"), such as cesspools and seepage pits,
may successfully "dispose" of the effluent (in that it is not visible to the property occupants) but are unlikely to
successfully "treat" the effluent to make it sanitary. While such systems may appear to be "working" and may remain unregulated by
local health officials, they are likely to be contaminating nearby ground water, streams, and possibly the drinking water supply.
Mound Systems and Dosing Systems WARNING: mound system using a pumping station are often designed to use
pressure dosing, pumping water to the mound at intervals, usually once per day.
Timed application allows the mound to rest and prevents unnecessary clogging
in the distribution system by maintaining aerobic conditions. Overloading of
these systems during testing could damage the septic system.
Maximum sewage loading rate to trench and bed in gallons per square foot per
day varies depending on soil percolation rate but ranges from .025 to 1.75
GPFD, with the lower numbers for beds than for trenches. (Ref. 14.)
Pumping tank working capacity is (typically) 25% of the daily sewage volume; actual tank
capacity should be much larger than this, at least one day's sewage volume.
Vehicle traffic:
Driving heavy vehicles over the mound can damage or destroy it. Typical mound
life is 20 years.
During testing watch closely for seepage at the perimeter or "toe" of the
mound.
We recommend limiting the test volume on mound systems to the pumping tank
working capacity. This might be as small as 125-150 gallons.
Trees and stumps may have been disposed-of below the area to be filled as a septic mound. This
"disposal" helps the builder by adding volume and saving on trucked-in fill to form the absorption system.
If you see tree trunks extending out from the base of a septic mound this condition is likely - and improper.
Pumping a Septic Tank Before Testing:
Do not permit the septic tank to be pumped before the septic loading and dye test - that
will prevent a valid test of the system and in particular, prevents loading of the drainfield.
More details about the problem of septic tank pumpouts as a cover-up of a septic problem or failure
are at Don't Pump Before Testing Septic Systems:
warnings for home buyers about septic tank pumping.
Replaced Septic Tanks: When a septic tank has been replaced but connected to an older existing leach field there is increased risk that
problems with the previous (failed) tank may have pushed solid waste into the leach field before the tank problem was discovered.
If this is the case, which would be common, one should expect that even if the leach field did not fail during a loading and dye test,
its future life will be more limited than otherwise.
Steel septic tank warnings: older septic systems often used steel tanks which eventually rust out and have to be replaced.
A damaged tank can also result in costly damage to the leach field or seepage pits.
Opinions of steel tank life range from 15-30 years. If a property is served by an old steel tank it could require replacement at any time.
SAFETY: Child or Adult Safety Hazard: If an older steel tank (or a home-made system) is found or suspected to be present the owner should immediately
protect the area over the tank from access: rotted or rusted covers can collapse and a child or adult can fall into the tank -
an event which can be fatal. Also, watch for and investigate any areas of soil subsidence quickly.
Other Septic Dye Test Limitations: Dye can identify certain kinds of septic failures, but not others.
By itself a dye test is not indicative of overall condition of the system. The
probable locations of tank and absorption system are inspected before, during,
and after a loading or dye test if these were ordered.
Ground conditions such
as snow, ice, leaf cover, can make it impossible for the inspector to see
dye-colored water even if it is leaking to the surface. Reasonable care was
used in determining the location of the components. However because these
components are buried, no guarantee can be made regarding the location nor
condition of private waste system components unless specific additional tests,
involving opening tank, pumping, and possibly excavation, are ordered. These
tests are not usually part of a home inspection unless preliminary examination
shows an apparent problem.
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Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Pollard Water source of septic system testing tracer dyes
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