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How to Perform a Septic Loading & Dye Test: Septic Testing Procedure Details
- a chapter of "Inspecting, Testing, & Maintaining Residential Septic Systems"
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• How to perform a septic loading & dye test, step by step
• What to do before, during, and after the test
• How much septic dye to use
• How to report septic test results
• Septic Test warnings and pitfalls

This chapter provides details of the Septic Loading and Dye Test procedure for testing the function of septic systems, focused on condition of the effluent disposal section, also known as a leach field, seepage pits, drainfield or drainage field. Septic System Loading and Dye Tests often requested by certain lenders, involve flushing a special dye down a toilet or other drain combined with a known quantity of water sufficient to put a working load on the absorption system. If waste water leaks to the ground surface (an unsanitary condition indicating serious septic failure) one may find dye in that water provided the septic system is flowing at common rates.

Dyed effluent usually appears in 20-30 minutes on a failed system but can take up to five days to show up. If at a building inspection suspect wet areas are observed I recommend a dye test even if one was not previously requested. When wet areas are not found (or created by running water into the septic system) on the property being inspected, dye tests may still be performed to meet requirements of some lenders.

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.

Use of this information at other websites is prohibited; reproduction in electronic or printed form is prohibited. © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website.

HOW TO PERFORM a SEPTIC DYE TEST - How to Properly Conduct a Septic Loading and Dye Test

Septic dye tests involve flushing a special florescent dye down a toilet or other drain. The dye itself does not make anything happen. It is simply a colored indicator that can identify water found outside as having come from the fixture where the dye was introduced.

It's the volume of water introduced into the system that forms the actual "test". If waste water is coming to the surface (an unsanitary condition indicating serious septic failure) one may see dye in that water, provided the septic system is flowing at common rates.

When suspect wet areas are observed, if the system has no maintenance history, if the area is known to have problem soils, or if other historic or site conditions raise question about the condition of the system we recommend that the inspector perform a dye test.

A septic loading and dye test will by no means find every septic failure, but this methods finds many failures that otherwise are unnoticed by a home buyer until shortly after moving-in. Septic loading and dye tests are complimentary to and should precede any further inspection steps taken such as pumping the septic tank.

WHAT TO DO BEFORE - the Septic Inspection and Test

• Septic Inspection Safety: Review Safety Warnings to Septic System Inspectors in our main text: "Inspecting, Testing, & Maintaining Residential Septic Systems.
• Questions To Ask the Property Owner About the Septic System
• Where are the septic tank and other system components located? (For help locating septic tanks see Tank Location - How to Find the Septic Tank)
• What is installed? (Steel tank, concrete tank, drain field, seepage pits, drywells, galleys, etc.)?
• What is the maintenance and repair history of the system? (Last pumped, what repairs have been done, pumping history and frequency, backups, etc.)

These questions are deliberately a bit vague and open ended to permit a property owner to volunteer what information they may have about the condition of the septic system. Because an owner may not recall the septic system maintenance history or may not be familiar with onsite waste disposal terminology, the inspector and client should obtain and consider but should not blindly rely on simple oral statements about the type of equipment installed.

These questions can be given to the inspector's client well before the site inspection, to permit the client or real estate agent to present them to the property owner, particularly if the owner is not going to be at the site at the time of the inspection.

• Obtain Permission: by informing the real estate agent and through agent an owner, or if owner is present, ask the owner's permission before performing this test.
  
  
• Do Not Pump the Septic Tank Before the Test - an owner who offers to provide this service for a prospective buyer may be (inadvertently) preventing a valid septic loading and dye test. We want the system to be in-use or at least the septic tank to be at its normal level of liquid and waste (its normal condition) at the time of testing. 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.
  
  
• Confirm that the septic tank has not just been pumped before starting a loading and dye test, by visual inspection and by asking the septic system maintenance history. If the inspector sees fresh excavation in a likely septic tank location it is possible that the tank was pumped recently. If the system has not been used sufficiently since pumping the septic loading and dye test should be postponed until the tank has first been filled. Otherwise the "loading test" is simply filling the tank rather than pushing any liquid test volume into the drain field.
  
  
• Septic system records: Are there written records of septic system installation, repair, or maintenance? Home inspectors performing a septic loading and dye test are not required to review written records nor to perform offsite research at a health or building department facility. Some inspectors may elect to offer that service for an additional fee.

Navigating in the Septic Dye Test Procedure Text

If you are reading by scrolling down in this document instead of using the links at left, be sure to read OUTSIDE INSPECTION - Simple Visual Site Inspection Gives Key Information About Septic System Condition Use the links at the left of our pages to continue to navigate this DOCUMENT and Our Website.

STEP BY STEP - Septic Loading & Dye Test Procedure

INSIDE STEPS - What to Do Inside the Building

• Locate and inspect key inside septic system components:
• Location of the main house waste line exit point and cleanout.
• Location of any other drain lines leaving the building, possibly suggesting more than one septic tank or drywell
• Location, type, number of plumbing fixtures. Are there fixtures that are unlikely to be draining into the septic system because of their distance or elevation?
• Location and types of septic system pumps and alarms
• Report components that appear to be installed but which were not readily accessible for inspection.
  
  
• Run bathtub or sink water (cold faucet only) or similar fixture closest to where dye will be introduced (typically at a toilet in the next step).
  
  
• Confirm water flow into septic: Inspect DWV lines, particularly in the basement or crawl space, to assure that the water being run is entering the septic system (as opposed to sinks and tubs being routed to a drywell while the toilet (and dye source) is routed to a septic system. Check that the drains are in fact connected and not spilling into the building. (E.g. where traps were removed for winterizing.) Confirm that water flow from fixtures being run is going into the septic system or document that such confirmation was not possible. Often by running a test fixture the inspector can find and listen to the main waste line, confirming that the fixture is flowing into that drain. An access port at a septic tank may also permit this verification.
  
  
• Flush the toilet with clean water where dye will (later) be introduced, assure it flushes normally so that you won't spill dye from an overflowing toilet into the building. Do not put dye into a toilet or other fixture before you have confirmed that the fixture will drain rather than backup and overflow into the building!
  
  
• Introduce dye into the toilet.(MUST use enough dye to stain no less than the volume of the septic tank. Typically this is 10 pellets or more and 2-3 tablespoons of dye. See the specs on the dye you buy and see DYE WARNINGS below. Some tablets are so weak you'd need 200 to stain the tank!)
  
  
• Record start time and estimated flow or measured GPM. Record all other pertinent descriptive factors as listed below.
  
  
• Run additional plumbing fixtures to obtain your total flow in GPM into the system and document which fixtures were run and the total GPM estimated or measured flow rate. Note that if the building is served by a private pump and well, the flow rate is not constant. The flow rate will vary as the pump on-off pressure cycle varies.
  
  
• Occupancy/Usage recording: note occupancy or time since last occupancy; note number of occupants, number of bedrooms, number of bathrooms. Observe and record separate handling of gray water and assure it's being discharged to an approved location (not surface nor storm drains) if it's not flowing into the septic system.

  If the system has been recently pumped, or if a cesspool is installed, this test may be invalid: it may not be possible to run enough water during the test period to fill an empty or partly empty tank or cesspool.

WATCH FOR INSIDE - What to Watch For Inside the Building

• Check for in-building drain leaks: At the start of your septic dye test, inspect the fixture drain and (if a basement or crawl space expose the drain piping) check for other leaks in the building. Once, with permission of the owner, we began a dye test from the second floor of a building only to hear screams of horror from the occupants of the floor below as red dye erupted from their ceiling. Always be sure that there are no leaky traps or drains before you leave water running in a building.
  
  
• Watch for sewer line backup in the building - indicating system blockage. Check all fixture drains before leaving water on. Check floors below running fixtures for signs of current or previous leaks. Don't risk flooding or damaging the building by leaking or overflowing fixtures. If leaks prevent testing, document this information. Check fixtures periodically during the test period, to assure no leaks or overflows.
  
  
• Find the waste line: If you didn't do this before, locate the sewer pipe exit point in the building. Confirm that the tub/sink drain for the fixture being used to load the system is in fact draining into the sewer line. It is important to take this step early in the test cycle, and to check all building areas to be sure that you are not inadvertently spilling water (and dye) anywhere inside.
  
  
• Confirm test water runs in septic drain line: Feel and listen to sewer pipes to assure that water is running through them to the sewer system.
  
  
• If this cannot be established or if only toilets drain into the septic system it may be necessary to use a garden hose to provide water into the toilet to test the system, or to warn the owner/client that the test is inconclusive for this reason as well as other limitations. (Beware of unsanitary cross connections; don't leave the hose in place when finished.)
  
  
• Trace all sewer piping (note visible components, report areas where there was no view or no access). Note locations of kitchen, laundry, bathrooms. If there is more than one exiting sewer pipe, introduce a different colored dye, and begin an additional test of measured flow at the appropriate fixtures. Record bathrooms that may have been added since original construction (permit may have been required.)
  
  
• Check lowest plumbing fixtures for backup: Check for bathroom fixtures at house level lower than exit point of main sewer line. Confirm presence and operation of appropriate sewage ejector pump or other permitted destination for such waste lines. Watch for septic backup and overflow from fixtures low in the building - during your test if the main waste line is blocked, or perhaps you will see evidence of prior backups and overflows.

OUTSIDE STEPS - What to Do Outside the Building

• Record weather conditions (heavy rain, snow cover, frozen snow, flooding, drought, etc.).
  
  
• Trace the sewer pipe, if possible, from the point of apparent exit from building to locations of apparent or plausible septic tank and absorption system. Clues such as depressions, rectangular or circular tank outlines, mature trees crowded together and larger open areas may indicate where components could possibly have been installed. (Excavating equipment may not fit among large old trees; very rocky areas may not hold septic components.)
  
  
• Examine the absorption area for signs of trenches, such as sunken parallel lines. Do this before starting the test, during the test, after the test, and up to five days after the site inspection (an added service or an admonition to the client) since it is possible in odd cases for effluent to appear on a property days after the initial test. Fortunately, in cases of a failed or marginal system this procedure often shows breakout in 20-30 minutes
  
  
• Note the locations of and distance to well, trees, pools, additions to the building, driveways, etc. that might infringe on the tank or absorption area.
  
  
• Examine all site areas including property boundaries that could reasonably be reached by drainfield extensions, nearby streams, ponds, storm drains, edges of mound systems, edges of banks, rocky areas, steep slopes near the septic fields
  
  
• Do not probe the soil over suspected septic tank locations by using methods that could damage the equipment. Heavy wrecking bars, for example, can puncture a steel or fiberglass tank cover or break a plastic drainfield line.

Navigating in the Septic Dye Test Procedure Text

If you are reading by scrolling down in this document instead of using the links at left, be sure to read FAILURE SPOTS - Where Septic System Trouble is Likely to Show Up Regardless of Dye Testing Use the links at the left of our pages to continue to navigate this DOCUMENT and Our Website.

After reading FAILURE SPOTS be sure to read SPOTTING BREAKOUTS - Spotting Dyed Septic Effluent Breakout Outside - Where Septic Dye is Likely to Show Up During a Septic Dye Test Use the links at the left of our pages to continue to navigate this DOCUMENT and Our Website.

The SEPTIC DYE TEST PROCEDURE continues below with information about the amount of septic dye to be used during a septic loading and dye test.

VOLUMES & DYE AMOUNTS - Table of Septic Dye Test Volumes and Septic Dye Requirements

CAUTION: appropriate test volumes may vary depending on the type of equipment installed. Some designs, such as dosing systems, may be approved by local officials but may be capable of only very limited fluid handling capacity per hour. Information provided by seller, realtor, visual inspection, or neighborhood history may indicate if special limited-capacity systems are installed. The following guidelines pertain to conventional tank and absorptions systems such as tank and trench-line drainfields.

The following table is a general guide to selecting the volume of test water and the amount of septic tracer dye needed to perform a septic loading and dye test. If you're asking "how much septic dye" or "how many septic dye tablets" should I use, look here and also look at the instructions from the manufacturer of your septic dye.

Notes to the Table of Septic Dye Test Volumes and Dye Amount

DETERMINING TEST VOLUMES - Recommended Septic Loading: How to Determine Dye Test Water Volume, and Amount of Septic Dye

FIXTURE FLOW RATE - Estimate the test fixture flow rate during a septic test

Based on field experience, actual test measurements at 25 residences served by private well systems and observations of typical flow and pressure at residences served by municipal water supply systems, we find that 3 gpm is a reasonable estimate of flow from a single tub or un-screened sink fixture. Most private systems can deliver this volume.

Actual quantitative flow rate measurements taken at a single fixture at a single time are dangerously misleading since variations in pump pressure, pipe obstructions, valve settings, can affect flow.

If accurate quantitative measurement of flow rate is needed, and remembering that you're measuring the flow provided by the pump, pipes, valves, and fixtures, not the well flow capacity, a simple procedure is the use of a 5-gallon bucket under the test fixture, and a stopwatch. However multiple measurements may be needed to evaluate the variation in flow rate during the pump on-off cycle.

SET THE TEST VOLUME - determine the septic loading test water volume

Some authorities commonly test by loading the system with 50 gallons/bedroom over an hour - the likely maximum load for a typical residential system. A typical trench-type absorption field would contain this volume of water even if there were no percolation during the test period. Therefore breakout or failure at these volumes is a reasonable sign of system failure or inadequacy.

Typical septic system design handles 150 gallons/bedroom/day. [Ref. 30, Oberg, citing "Private Water Systems Handbook," produced by the US Dept. of Agriculture Cooperative Extension.]

Lockwood in our own article Septic Systems - An Engineer's View uses this same figure of 150 gallons/bedroom/day to estimate water usage in a typical residential building. Also see Home & Outdoor Living Water Requirements for more detail.

Keith Oberg (ASHI, Binghamton NY) computes that a standard leach line for soils in central NY range from 90 lineal feet with a 3 foot wide trench and a percolation rate of 1" in 5 minutes, to 375 lineal feet of 3 foot trench with a perc rate of 60 minutes.

The gravel in a standard trench leaves approximately 38% of total volume available to contain effluent. Therefore, assuming no percolation during the test period, the water level will rise 2.35" in a 90' trench and .56" in a 375' trench. (Double these depths for more narrow gravel trenches.) These are not excessive increases in a leaching field which is typically set at least 12" below the surface with 18" depth of gravel as standard practice. It is therefore apparent that an adequate septic system should not break out when subject to this test.

Oberg applies this same test to all septic systems of all types, including sand mounds, sand filters, aeration ponds, jet aerators, drywells, cesspools, etc. If there are multiple systems the water load is split on each system and a 33% extra water load is added to account for errors in estimation of the percentage of total use.

Navigating in the Septic Dye Test Procedure Text

If you are reading by scrolling down in this document from VOLUMES & DYE AMOUNTS then if you missed STEP BY STEP you skipped text which explains how to conduct a septic dye test and you missed reading how to spot septic dye breakout outside. Use the links at the left of our pages to continue to navigate this DOCUMENT and Our Website.

REPORTING TEST RESULTS - & Test Conditions - What is the Minimum That A a Septic Test Report Include

A septic loading and dye test does not guarantee detection of all failing conditions. However it can make a meaningful reduction in the risk of an imminent costly septic failure, if the test is performed and documented properly. For a test to be meaningful, it is critical that reasonable test procedures be followed, such as described above, and that the procedures are documented.

A professional inspector is expected to provide sufficient documentation of the procedure followed and results obtained that an experienced third party could review that information and agree that the test provided was acceptable, regardless of the outcome. Finally, proper documentation at the site and during the test makes writing the septic report much easier.

The meaning and reliability of any test procedure is obscure unless the consultant records the test parameters and conditions. For example, a "dye test" was performed by an inspector who placed a single dye tablet into a washing machine drain line, followed by running 50 gallons of water at an upstairs plumbing fixture.

The lack of aggressiveness of the test, inadequate dye amount, minimal volume of water run, and failure to confirm that the fixture operated actually placed water into the septic tank all would have been more obvious to both the inspector and the client had this date been reported. Instead, the inspector wrote that he had "performed a septic dye test" and that there was "no evidence of a problem."

In an often-occurring anecdote, the morning after the new building owner moved into the home, sewage effluent had flooded the yard behind the home. When the septic contractor opened the tank it was evident that the tank was totally packed with solids. Litigation followed. This sounds like an extreme example, but it's all too common.

Essential documentation of septic loading and dye test procedure and conditions includes at least the following:

• Administrative details: Inspector's name and contact information, client name, property address, inspection date, time, and pertinent weather conditions
• Safety: Observations of visually obviously unsafe conditions at the property such as the presence of cesspools, bad tank covers, open pits, subsidence or collapsing equipment.
• Test Limitations: Observations of conditions which limited the test or which added risk of the septic test having been subverted: recent application of bleach, damaged tank (low liquid levels), or reported maintenance history of the system
• Pre Test Conditions: Observations before attempting the test: odors, wet conditions, grass color, rocky site, etc.
• Plumbing Fixtures Operated: Location and identity of plumbing fixtures operated during the test, for placement of dye and for placement of the test volume of water into the system.
• Septic System Components: Observation of or reported type of septic system components: tank (concrete, steel, reported size), reported absorption system type (drainfield, mound system, pump up system), presence of pumps (single vs. duplex), alarms.
• Components not tested: such as drywells or other components which are known to be present or for which there is strong suggestion of their presence (such as graywater lines leaving building locations at points remote from or below the elevation of the main drain.)
• Septic Test Parameters: Estimated total test volume of water used. Details may include fixture flow rates and flow duration. This information should include confirmation, or inability to confirm, that the test water entered the septic system.
• Indications of septic system failure:
• Presence of effluent or dye surfacing or breakout at the yard surface during and after the test.
• Marked change in the wetness or softness of ground over the suspected leach area (as compared with that observed at the start of the test)
• Septic odors
• Discharge of septic effluent or graywater to the surface or to a nearby pond, lake, stream, drainage ditch, etc.
• History: Information regarding the system history and maintenance if such were reported to the inspector by the seller or realtor or another party
• If there was historical, visual, or test results that indicate or strongly suggest that the system is in-failure or that it is in very questionable condition, the report should include an explanation of these site observations, system history, and test results such that the client has an opportunity to understand the significance of the findings and reasonably probable need for repair.
• Conclusions: there was or was not visual or historical evidence of the need for septic system repair or replacement. Other recommendations for maintenance or further investigation (such as tank pumping and inspection, D-box exploration, etc.)

An example field data recording sheet which includes a section on Dye Test Procedure Used (fixtures operated, total volume run, confirmation of flow into septic) and pre and post-test Observations such as and evidence of dye breakout is provided at Level 0 - Basic Septic Inspection Worksheet

PUMP THE SEPTIC TANK - After, not Before Testing

After a loading and dye test (which primarily tests the absorption system, leach field, or drain field), unless the septic tank has been pumped very recently, we recommend that this additional step be taken.

Before completing the purchase of a property with a septic tank and absorption system, limited but important additional information regarding the condition of the system tank and also the leach field may be obtained by having a septic contractor open, clean, and inspect the septic tank itself.

Particularly in the case of older systems that have not been serviced, if the property owner will permit this step we recommend it. When the tank is pumped, ask the pumping contractor to describe the size, type, and condition of the tank and its components, and also to tell you if s/he saw any indications that the system needs repair or that the tank or leach system are at or near the end of their life.

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.

DYE TEST WARNINGS - Septic Inspection & Loading/Dye Test Warnings

• Septic Inspection Safety: Review Safety Warnings to Septic System Inspectors in our main text: "Inspecting, Testing, & Maintaining Residential Septic Systems.
  
  
• 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.

The Septic Systems Online Book - Where Are We?

More Information About Septic Systems - Onsite Waste Disposal Design, Maintenance, Repair

• Return to the septic system textbook: Inspecting, Testing, & Maintaining Residential Septic Systems
• The Septic Information Website
  
  
• Safety Warnings to Septic System Inspectors
• Testing Water for Real Estate Transactions - Water Test Cheating Warnings for Home Buyers and Home Inspectors.
• Home & Outdoor Living Water Requirements
• Septic Tank Capacity vs Usage in Daily Gallons of Wastewater Flow calculating septic tank volume and septic tank size required
• How Big Should the Leach Field Be? - table of soil percolation rate vs. field size
• The Home Buyer's Guide to Septic Systems
• Material Safety Data Sheet MSDS for Red Septic Dye from Tramfloc.
• MSDS for Septic Dye Tablets from Tramfloc.
• MSDS for Septic Dye Liquid from Tramfloc.
• Septic Dye Technical Data Bulletin from Tramfloc.
• Tramfloc, Inc. source of septic system testing tracer dyes
• Bright Dyes Inc. source of septic system testing tracer dyes
• Pollard Water source of septic system testing tracer dyes

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