This article explains how we determine the Life Expectancy of a Septic Drainfield ?

How long should a leachfield last? - among the types of septic system failure in the drain field, leach field, seepage bed, or similar component. We list the causes of each type of septic component failure, and list the septic component failure criteria or in other words what conditions are defined as "failure"?

How can you distinguish between a blocked pipe, a septic tank that needs pumping, and a clogged drainfield that needs replacement? This is an important question as it distinguishes between relatively low cost maintenance or repair task and a costly septic leach field replacement.

Septic System DRAINFIELD LIFE Expectancy - What destroys or shortens the life of the absorption system?

We have seen drain fields still working fine after 25 years and others which failed in the first week of occupancy of a new home. In a properly designed septic absorption field the level of usage of the system, site characteristics such as slope, rock, groundwater level, and soil percolation rate have all been considered.

Barring foul ups such as we discuss in this document, such a field may last from 10 to 20 years. USDA sources assert that a properly operated and maintained ST/SAS (septic tank / soil absorption system) should last at least 20 years.

But it's easy to ruin or shorten the life of a drainfield/leaching bed. In fact the same USDA source states that

Studies reported at an Environmental Protection Agency seminar, Orlando FL, November 1979, show that over half [ST/SAS] fail prematurely due to improper operation or lack of adequate maintenance.

Generally, these failures occur when the soil-absorption system [drainfield] becomes clogged.

Preventable clogging, due to a buildup of solids in the [septic] system, is usually extensive enough to require expensive reconstruction of the system. Failures can also cause nearby ground areas, streams, lakes, and water supply systems to become contaminated.

This exposed the public [and USDA, EPA, NPS, FPS, and other government employees] to health threats such as hepatitis, typhoid, diarrhea, and dysentery.

... [ in contrast] The unpreventable failure of the soil-absorption system eventually occurs when growth of the organic material in the wastewater [the biomat (SEPTIC BIOMATS) that forms under and along the sides of a drainfield trench] becomes so large [thick] that they plug up the soil.

Similar studies of advanced wastewater treatment systems such as aerobic systems, sand beds, mound systems similarly found that improper or inadequate operation and maintenance were the primary causes of premature failure of those systems as well.

Notice that our sketch at above left specifies 2-4 feet clearance between the bottom of the drainfield trench and the seasonal high water table. Code requirements on this distance vary, but the point is that even if septic effluent appears to be successfully disposed-of, it may not be adequately treated if the drainfield is not constructed properly. Image (above left) courtesy USDA.

For a better view of the probable life of a specific drainfield at a specific property you'd want to know the

• installation details of the drainfield including clearance over high water table, adequate dimensions for usage and soil percolation rate, provision of an adequate trench size and quantity of and proper type of gravel, inclusion of a barrier material over the rock, gravel, or stone surrounding the leach lines
• septic system effluent discharge method: gravity, pumping, alternating bed, dosing system, surges in use
• level of usage of the drainfield - how much wastewater the soakaway bed or drainfield has had to handle and has the daily wastewater flow regularly exceeded the system design flow parameters
• soil conditions under and around the drainfield, surface runoff, groundwater, seasonal flooding and so on
• maintenance history of the septic tank - when has it been pumped and what conditions were observed
• results of any recent septic drainfield inspections and tests

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-04-29 - by (mod) - effluent bubbles up in my front yard; proposal for septic restoration

Laurie

Please take a look at SEPTIC DRAINFIELD RESTORERS?

In my opinion there is no failed drainfield restoration process that has, by independent, unbiased third party assessment or academic study, shown that those treatments or processes are durable, nor that they add much useful life to a failed drainfield. If you can get a septic drainfield completely replaced for just $2000. USD, in my opinion that's a better approach.

OPINION: Magical thinking invades not just some of our government but also normal people facing annoying costs. Magical thinking is usually at best a waste of time and money, and sometimes, dangerous.

On 2020-04-29 by Laurie Biederman

Hi: I have lived in my house for almost 11 years, have septic, which have cleaned routinely, although just had cleaned after 4 years most likely, too long. About month ago started smelling foul odor. With all rain, bubble up of effluent in front yard.

Septic co. came, he said he'll contact our town and see, feels was repair in front yard, I knew nothing about it. He says the fix is either a machine that fractures holes in yard, is that to release water or alleviate plugs in line?

or failing that, which he says will cost 2K, it would be too replace the fields, 10-30K!!! Should I get a second opinion after he lets me know what the town tells him? Thanks for your advice!

On 2020-03-05 by Anonymous - When installing a septic drainfield, workmanship is critical.

Rita

When installing a septic drainfield, workmanship is critical. There is no manufacturer warranty that has any meaning whatsoever in my opinion. What the heck is being warranted?

That a perforated plastic pipe won't "fail" by collapsing. Nonsense. It's proper slope, depth, gravel-bedding, grading, soil conditions, layout, design, etc. that are critical.

A simple stupid mistake like puttting in a drainfield in seasonally wet/flooded soils is a failure from day one.

On 2020-03-05 by Rita

The quotes are for installation of a new drain field.

Some of my quotes are giving a 3 to 5 warranty for workmanship. Should I go with a contractor that only gives a manufacturer 2 year warranty?

On 2019-03-07 by BUD MOODY

Thanks for the suggestion; another inspector coming out Tuesday, hopefully we'll get a handle on what the problem is.

On 2019-03-07 - by (mod) -

Most likely that's an inadequate total volume for a septic test.

Nevertheless, sorry to say, it looks as if there is a problem, but without more diagnosis we don't know if it's a clogged pipe or failed fields.

Gheck in The d box

On 2019-03-07 by Anonymous

, Garden hose in the tank for 7 minutes at roughly 15 gallons per minute. So he put about 105 gallons into the tank.

On 2019-03-07 - by (mod) - 7 minute garden hose leach field test?

It's not a test procedure that I would use nor one that's familiar to me.

However if the tank floods when waste water is entering it that's a sign of a slow Outlet which could be a blocked drain line or a failed Greenfield.

It sounds as if your inspectors test indicates that the tank was basically flooding.

To make sense out of what he did you would also need a time and volume estimate of how much water was put into the tank over what period.

On 2019-03-06 by Bud

We are purchasing a home with a septic system; the inspector failed the leach field. No evidence of leakage outside, to evidence that the levels went over the baffles in the 1500 gal tank.

He did the following test: ran a garden hose full on into the uncovered tank for 7 minutes until the outlet was completely submerged

and then noted that it took 75 minutes for the fluid level to return to normal. He noted that the outlet "T" was intact, but didn't note any inspection of the interior of the outlet T or the distribution box. Is this an adequate test to fail a leach field?

On 2018-11-25 - by (mod) - my graywater tank won't drain

Michael,

In the ARTICLE INDEX you'll find a series of articles on how to find the D box or distribution box that would be a good place to do some investigating.

If the d-box is flooded then the drain field or the lines to it from the d-box are clogged or failing.

If the d-box is dry then you need to scope or clear the line between the septic tank and the the d-box

On 2018-11-24 04:1 by Michael Bagley

My gray tank will not the water to Drain.

I have my tank pumped 3 time
This year. I think there's clogged somewhere. I hope it's not the lines.

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Continue reading  at SEPTIC DRAINFIELD INSPECTION & TEST or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see SEPTIC DRAINFIELD LIFE FAQs - questions and answers posted originall

Or see these

Articles about the life expectancy of a septic system

• BLOCKED DRAIN REPAIR METHODS - be sure the problem isn't just a clogged drain
• CLOGGED DRAIN DIAGNOSIS & REPAIR
  
• NO ROCK SEPTIC SYSTEM LIFE
• SEPTIC BIOMATS - what is the septic biomat and how does it lead to field clogging or failure?
• DRAIN DRAINFIELD DIAGNOSTIC TABLE
• SEPTIC DRAINFIELD LIFE
• SEPTIC DRAINFIELD RESTORERS?
• SEPTIC LIFE EXPECTANCY
• SEPTIC LIFE MAXIMIZING STEPS
• SEPTIC FIELD FAILURE CAUSES
• SEPTIC SYSTEM AGE
• SEWER BACKUP PREVENTION

Suggested citation for this web page

SEPTIC DRAINFIELD LIFE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to SEPTIC SYSTEMS

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Citations & References

In addition to any citations in the article above, a full list is available on request.

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