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Drain Field Problems: Why They Happen and How To Fix Them

Updated: Oct 11, 2023

When it comes to home septic maintenance, don't overlook the important role your drain field plays. Problems with the drain field can be a severe issue that can affect the entire system if they aren't promptly repaired. Fortunately, it's usually simple to spot issues if you know what to watch for.


There are a few obvious symptoms of drain field failure. Knowing what they are can help you spot problems early on, when they may still be minor enough to be easily repairable.


Septic odors are easy to identify, as they smell like raw sewage or are reminiscent of rotten eggs. A properly working drain field is free of bad odors since the effluent should be deep within the soil surface being filtered by natural processes. Odors only rise to the surface of a drain field when something has gone wrong.


When effluent can't properly flow into the drain field, it backs up into the septic tank. Then, like a domino effect, the excess in the tank will back up into your home. Overflowing drains and toilets can indicate severe issues, but even drains that are emptying slower than usual should set off a red flag. If the tank is properly cleaned and maintained, then it is very likely that the drain field is the origin of the problem.

Field Qualities

A properly functioning drain field should have firm soil underfoot and healthy lawn or meadow plant growth on top. Field qualities that signal possible problems include spongy or wet ground, even if the weather has been dry, or an overgrowth of the grass and plants covering the field, especially if it is patchy. Too much water, combined with the excess nitrogen from unprocessed effluent, causes these quality changes.


A variety of issues can affect a drain field, but they really boil down to three main issues. Determining the exact issue can help you pinpoint what is causing it.


Drain field designs vary, but all are susceptible to damage from compaction problems. The ground over the drain field can become compacted by driving or parking upon it, or by constructing a building on it. Roots are also a common cause of compaction, particularly if tree or shrub roots invade the drain field. The trees don't even have to be in the drain field, as roots can invade from nearby plantings.


Common causes of flooding include excess rain fall or snow melt, water incursion from nearby bodies of water, and irrigation runoff. Regardless of the cause, when excessive water floods a drain field the system won't be able to properly compensate, which means unprocessed effluent may rise to the surface. Further, fresh effluent from the tank may be unable to flow into the over-saturated drain field.


A drain field is not immune to clogs. Leach lines in the field can become clogged with debris in the effluent. This is often the result of an overly full septic tank emptying out unprocessed solids into the field. Damage to the tank, such as a malfunctioning baffle, can also be the culprit. Other issues are putting items down drains—such as "flushable" wipes—that shouldn't be fed into a septic system.

Repair Options

Repair is unavoidable in the event of a drain field problem. Otherwise, you risk failure of your entire septic system, which poses a risk to the environment and to human health.


Sometimes the repair is as simple as cleaning and servicing the drain field lines. This includes inspecting the baffle and main drain line that connects the tank to the field, and then making any necessary repairs or replacement to the components. The actual lines that cross the field may also need to be augured out to clear them of clogs, tree roots, and collected debris.


Flooding and water incursion problems can sometimes be fixed by expanding the drain field so that it is large enough to handle periodic influxes of extra water. Extra drain field is most often installed in an area that is less effected by seasonal flooding. If the issue is irrigation runoff, then it may also be necessary to re-route runoff flow so it doesn't go toward the drain field. Ideally, irrigation water shouldn't pass within 10 feet of your drain field.


In cases of severe damage, typically due to compaction or major site issues that lead to constant flooding, replacement of the drain field may be necessary. This is an involved process that requires digging up the old field, replacing and repairing the soil, and then installing new lines. If necessary, the entire drain field may require a new site with fewer challenges. Keep landscaping to shallow-rooted herbaceous plants, such as ornamental grasses, to avoid future compaction issues.

Contact Abbotts' Construction Services Inc. if you are having problems with your drain field.

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