Septic piping failures - an expert can find clues and perform tests that reduce risk of a costly surprise

Home seller or home buyer guide to septic tank piping clogs, slow drains, or blockage
     


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Discovering clogged septic system piping during the process of buying a home: this article discusses how to diagnose and repair clogged septic systems or piping. Septic backups, failures, breakouts, odors: This document provides advice for home buyers who are buying a home with a private septic system: homes using a septic tank and drainfield or similar soil absorption system.

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.

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4-2 Septic or Sewer Line Drain Pipe Clogs, Damage & Failures

Septic Main Drain or Municipal Sewer Piping Failures - Distribution Piping

Photograph of a new plastic sewer line being installed. Photograph of septic or sewer line piping clogs and failure.

[Click to enlarge any image]

Distribution piping connects the house drain to the septic tank, running between the building and the tank inlet. More distribution piping connects the septic tank outlet to the distribution box and from there to the leach field. Distribution pipes can settle (especially in new construction), break, become blocked or clogged, or become invaded and blocked by tree roots or soils as shown in the first photo above. Clay pipes also break and have a tendency to become blocked by tree roots at their joints as happened here.

Older "orangeburg" pipes which look like black asphalt-soaked cardboard (they are) crush and deteriorate with age. You won't know what kind of piping is installed until it is excavated, but the age of the property may be a clue.

Homes built from the 1970's on, certainly from the 1980's on, use cast iron or more often plastic ABS or PVC piping for these connections, as shown in the second photo above where we were replacing a root and mud-clogged clay sewer line with a new plastic line.

See "Drain Line Replacement diagnosing a clogged drain leads to drain line replacement" for a step by step photo-illustrated guide to diagnosing failed septic piping (or sewer line) and the subsequent drain replacement procedure.

Septic Distribution Boxes

Photograph of a septic distribution box or D-box (US EPA). Distribution boxes serve as a connection point to distribute effluent which arrives from the septic tank outlet and is to be sent into two or more individual leach field lines. Distribution boxes ("D-Boxes") can settle or tip.

A damaged or tipped D-box will fail to divert effluent uniformly among the effluent receiving drainfield lines, causing flooding of one leach line.

If you see depressions suggesting that there are four leach lines at the property and the end of just one of them is producing wet soil or surface-breakout of effluent, we'd suspect a tipped D-box.

Photo courtesy U.S. EPA)

Details are at SEPTIC D-BOX INSTALL REPAIR.

Septic Drainfield Piping Clogging

Sketch of a drain field or absorption field, conventional septic system design (US EPA). Drainfield piping is usually constructed of perforated pipe buried in gravel-filled trenches. It receives effluent from the D-box and allows it to percolate or

seep into the soil around the trench where added filtering and bacterial treatment occur. Like the distribution piping discussed above, individual drainfield pipes can become crushed, shifted, or clogged by tree roots or other debris.

More general clogging and failure of the leach field is discussed below. A broken or clogged pipe, once it has been located, may be

much less costly to repair than a complete leach field replacement, so this possibility needs to be considered during diagnosis of a "failed" septic system.

We have more to say about septic distribution piping failures in the next section 4-3 where we discuss Leach Field Failures.

Sewer or Septic Tank Drain Line Backups & Clogs Due to Bends, Roots, Slope Defects

Reader Question: is a 90 degree bend in the sewer line causing clogs & backups of our septic system?

Hi, I'm a veteran with a recurring problem with a septic system installed in 2006. The tank is located approximately 25 feet from the house. The pipe leaves the house - runs approximately 25 feet then makes a 90 degree turn and enters the inlet side of the tank approximately 1-2 feet from the 90 degree elbow. I was experiencing recurring back ups approximately 3 times per year-most embarrassingly during a family gathering. We had the tank pumped in Dec 2011.

There are only 2 residents in a 3-bedroom, 2 bath home so the tank should have sufficient size to handle this. Have not had any known issues since. However, just recently got a back up. Each back up was successfully cleared by a roto rooter service - usually the clog seems to be right at the 90 degree elbow or at the inlet baffle area - can't really tell. I'm trying to understand the cause of these back ups. It's been suggested to re-pipe the inlet to create a long sweep turn versus the 90 degree elbow.

Not quite sure how this would eliminate the issue. If too much water is flowed into the tank - heavy wash day etc I can see how this might take a few minutes to flow through the filter and out to the leach field but why would a drain snake immediately fix the issue?

We use septic safe toilet paper, don't use the disposal, limit chlorine type cleaners, don't put grease or oil in the sink drains, regularly use yeast product to keep bacteria levels up. any advice or access to local expert in Metro Phoenix AZ would be helpful. thanks for any advice or things to check on. - J.C., Phoenix AZ 1/3/2014

Reply: quite possibly; notes on sewer line turns, bends, clogs & septic system / sewer line diagnosis & maintenance

A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone, and an experienced plumber might see some other problem such as a venting, pipe slope, tank baffle inlet or other problem, or even signs of a clogged, failing drainfield even though your immediate problem appears to be a drain issue (SEPTIC DRAINFIELD FAILURE DIAGNOSIS). You will find additional depth and detail in articles at our website.

Because there is often confusion between a septic system failure and a drain problem, we've written CLOGGED DRAIN vs SEPTIC PROBLEM to help figure out where the problem lies. But as you report that a drain cleaning snake ("roto rooter") has cleared the blockage and gotten the drainage system working more than once, I share your suspicion about the problem location - at that 90 degree turn of the waste line between the building and the septic tank.

That said I want to clarify the 90 degree turn problem. In good plumbing practice we would not ever install an actual 90 degree elbow in a sewer line. Such a sharp turn is indeed inviting clogs, even in steep slope or vertical drain sections. Rather the plumber will typically install two 45 degree bends to make a more gentle turn.

It makes sense to confirm that it's actually a 90 deg turn that was installed, and if so to replace it with two 45's. In the course of digging up that bend in the waste line, inspect the piping to identify the material and to confirm that there is no other damage. For example, in an older waste line that is cracked or broken open, soil spillage into the drain or root invasion into the drain can also lead to recurrent sewer line clogs and backups.

You can also take an initial step to confirm that there is or is not evidence of a problem in the septic tank and indirectly with the drainfield by opening and inspecting the septic tank at the inlet end of the tank. Check that the SEPTIC TANK BAFFLES are in place, un-damaged, and that the wastewater level in the tank is at a normal level. If you cannot find the septic tank see SEPTIC TANK, HOW TO FIND.

A few other comments on your note:

Without knowing the septic tank size I'm reluctant to assume anything about its adequacy, though I agree that a code-compliant septic tank installed in 2006 ought to have been matched to the anticipated number of occupants of the home. Similarly there can be hidden installation or other defects at any buried component such as sewer lines, cleanouts, a septic tank, distribution box or drainfield. But before starting any costly digging project I'd want to have some reason to suspect that the trouble and expense were justified. Put another way, it makes sense to try the easy, lower cost exploration and repair steps first.

You comment that the septic tank was installed in 2006. It's now eight years later - you ought to take a look at SEPTIC TANK PUMPING SCHEDULE . Armed with an idea of the septic tank size and the number of occupants in the home you can guesstimate how often you should be pumping the tank - a step that extends drainfield life.

Watch out: You comment that you use a yeast product regularly "to keep bacteria levels up". That is a bad idea, doesn't work, and can harm the septic tank and ruin the drainfield. Yeast levels have nothing to do with septic tank bacteria levels, and yeast can cause septic tank contents frothing and churning that forces solids into the drainfield, shortening its life. You do not need to use septic tank additives in a conventional tank and drainfield, and some of those products are both harmful and in some jurisdictions, illegal as well. Details are at SEPTIC TREATMENTS & CHEMICALS or select a topic from the More Reading links shown below.

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