Building Inspection, Diagnosis & Repair Info

A septic dye breakout over a septic leach field indicates field failure in this case - an expert can find clues and perform tests that reduce risk of a costly surprise Home Buyer's & Seller's Guide to Septic Drainfield Failures

  • POST a QUESTION or COMMENT about discovering a failed septic leach field or soakaway bed during the purchase of a home - what should a home buyer or home seller do about a failed drainfield?

Septic drainfield failure detection & actions when buying a home:

This article series discusses how to diagnose and repair Septic Drain Field Failures. We describe common causes of leachfield failures, and we give advice for home buyers or home sellers for the case when a septic failure is discovered during the home sale process.

This article series outlines what goes wrong with septic systems and their various components and describes septic inspection and test methods in 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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?


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Drainfield or Soakaway Bed Failures: Septic Leach Field Failures that Occur When Buying or Selling a Home

sketch of cross section of a drainfield trenchSome septic system repairs are comparatively modest, such as replacing covers or baffles.

Replacing septic tanks or leach fields is costly. No leach field has an infinite life, but proper septic system maintenance can defer this cost. Because costly septic system repairs may be upcoming, buyers of properties with a septic system are advised to inspect and test the system before purchase.

Clogged drainfield soils

[Click to enlarge any image]

The most common and normal drainfield end-of-life failure is clogging of the soils around the drainfield trench.

As we elaborate below, with time and age and normal drainfield functioning, a natural formation of a biomat around the drainfield trench ultimately leads to a thick slime layer that blocks wastewater passage into the surrounding soils.

But failure to pump the septic tank on schedule allows suspended solids and greases to flow into the drainfield, speeding up this clog-up process.

Pumping the septic tank on proper schedule and use of a septic filter are two steps that most add life to a conventional septic tank and drainfield design.

See details at SEPTIC TANK PUMPING SCHEDULE

and at FILTERS SEPTIC & GREYWATER

The sketch shows a conventional drainfield trench in cross section. As the drainfield line ages the soils become clogged around the distribution piping, starting first at the end closest to the septic tank or distribution box.

Eventually soils around the entire line are clogged with a thick biomat, or perhaps worse, by grease or salts that should have stayed in the septic tank. At this point the soil absorption system stops absorbing effluent. The soils around the leaching bed trenches have become clogged and stop passing effluent. Sending grease and floating solids into the leach field hastens this failure.

The biomat which forms below and around the sides the leaching beds will eventually also become too solid and impacted, stopping soil absorption. In this leach field photo effluent was appearing in the light colored area where the homeowner had begun some exploratory digging in a soggy spot only to see her hole fill up rapidly with effluent.

In the building drains become sluggish, stop, or back up into the building (unsanitary), or effluent may appear on the property surface when the absorption system can no longer function or where a pipe has become damaged.

Flooded Drainfield Soils

This costly surprise caused by building a swimming pool over the drainfield

A septic drainfield that has become saturated for any reason is no longer functional. Saturated leachfield or soakaway bed soils mean that the wastewater effluent is not being treated by bacterial action and that unsanitary wastewater is being discharged into the environment.

Our photo (left) shows several drainfield failure troubles: flooding over the drainfield and a nearby lake.

Depending on soil conditions, land slope and shape, and perhaps other conditions, a saturated drainfield may not be immediately apparent, but this failure shows up in the following ways:

Building on or over or too close to the leach field causes failures

This costly surprise (a septic failure) was caused by building a swimming pool over the drainfiel CLASS=

A leach field (or depending on where you live, drainfield, drainage bed, soakbed, soak pit, leach lines, septic trenches, or soil absorption system) that is supposed to absorb and treat septic effluent can be destroyed by other site "improvements" such as this attempt to install a swimming pool atop the leaching area in the photo shown at left.

This mistaken installation involved multiple errors: placing a pool atop the leaching area which prevents proper oxygenation and evaporation, driving over the leach field which risks damaging buried pipes and compacting the soil, and excavating to remove a portion of the absorption system soil to put in the swimming pool.

Compacted Soil Drainfield Failures

parking lot atop a possible drainfield location - likely to ruin the field by compacting the soils.

Compacted soils due to parking or driving on the septic drainfield: driving over the leach field in any vehicle larger than a child's bicycle is a bad idea.

Heavy vehicles may actually crush buried leach field lines, or they may compress the soils around the leach field, either of which leads to failure.

septic dye breakout shows a total septic system failure at a parking lot

Driving on or parking on leach fields will destroy them.

This property actually had no working septic system at all - 100% of its effluent was coming to the surface nearby, brought out by solid rock covered with shallow soils, and running down a steep hill into a local stream.

Paving over the leach field means not functional

A leach field cannot function properly if it is paved-over. Some folks may try this as a way to permit parking over the absorption system.

But paving prevents both evaporation of effluent (a portion of the effluent disposal method) and it prevents oxygen from reaching the soil, thus inhibiting proper bacterial action needed to treat the effluent.

D-box flooding indicates a septic field failure in house for sale, I can't afford a new drainfield. How to proceed?

Photograph of a septic distribution box or D-box (US EPA).Our reader asked:

I am having a problem. I am listing my home for sale and had the septic checked out today. The septic company dug up and pumped out the tank with no problems being noticed. He then dug up the D box and inspected it.

When he opened the lid system to the D box the water level was right up to the top of the box. He pumped out the D box and as he was doing that water (clear) was draining back into the D box from the field bed.

We have never had any problems with the septic system, we have it pumped every year since it was installed 18 years ago. The system has never backed up or over flowed on the lawn.

I did notice that the top of the septic tank is only 6" under ground and the top of the D box is 4.5 feet under ground. The distance from the center of the septic tank to the center of the D box is about 21 feet.

If you do the math that would produce a 21" per foot pitch. ?

Correct me if I'm wrong but I thought it should only be 1/4 per foot pitch. Please help I cannot afford to install a complete new system. Thank You. - G. 6/19/12

Reply:

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with the septic system, piping, or drainfield. You are describing a flooded D-box and a flooded drainfield.

That said, here are some things to consider:

If you could look into the Distribution box again and tell me the configuration of the exit lines as well as the layout of the drainfield we could make more sense out of this point. It could be worthwhile, because if 1/3 of the field is doing all the work and is flooded it may be possible to improve the system by temporarily blocking off that drainfield section. More about the septic system distribution box or dbox is

at SEPTIC D-BOX INSTALL, LOCATE, REPAIR.

But if water flows into the D-box from all of the exiting lines, then the entire field is flooded and not working.