Diagnose & Fix Clogged Drains & Septic System Backups
First Step in Drain Repairs for Building Owners/Managers

  • CLOGGED DRAIN DIAGNOSIS & REPAIR - home - CONTENTS: how to diagnose and fix blocked or clogged plumbing drains. What signs indicate a clogged drain? How do we distinguish between a clogged drain and plumbing vent troubles. What are the steps in fixing a clogged drain?
  • POST a QUESTION or READ FAQs about how to diagnose & repair slow or clogged building drains

How to fix a blocked or clogged drain: this article series explains how to troubleshoot & repair slow or blocked plumbing drains, diagnose & fix sewer line or septic system backups & how to distinguish between a probable septic system failure versus a probable blocked building drain or sewer line.

When a building drain or main sewer line is clogged or slow, or when there is a septic system backup, it's important to determine where the problem lies, since the repair steps can be quite different and costs can vary widely. Here in addition to a text-based explanation of how we diagnose blocked drains or related sewer line or septic system problems, we include in a drain & drainfield diagnostic table.

Green links show where you are. © Copyright 2015 InspectApedia.com, All Rights Reserved.

Clogged Drain Diagnosis & Repair: how to fix slow or clogged plumbing drains

Clogged shower drain (C) Daniel FriedmanFIRST SIGNS - What are the First Signs of Trouble Indicating Failure of a Septic System?

What should a building owner do if the building drains stop working or there are odors or sewage-suspect wet areas on the property?

It is important to distinguish between a simple blocked trap or blocked pipe and a failing septic system. That's because the remedies, as well as the costs, are quite different.

[Click to enlarge any image]

The photo at page top shows the final repair for a toilet that was backing up - in this case the drain was blocked by a child's underpants.

By following the investigative steps we recommend you can determine the difference between a blocked drain and other more extensive plumbing or septic system problems.

Our photo at above-left shows a clogged shower drain in an older home. That white blob of crud in the drain trap may be removed or pushed through by a plumbing snake. But if the building is served by galvanized drain lines, those may be blocked internally by rust or mineral deposits, leading to a more costly repair.

Is it a Plumbing Problem or a Septic System Problem - A First Look

A simple initial step must be taken to distinguish between an in-building plumbing problem and an (outside) on-site waste disposal system problem.

Simply put, if a single building fixture is sluggish or clogged, but if other building fixtures drain properly, you should suspect a local clog or vent problem at the individual fixture.

If all building drains are slow or clogged, or if waste is backing up into the building from the lowest plumbing fixture, you would suspect the onsite waste disposal system.

Details to help you make sure that you know whether the clogged or slow drains or backed up drains are due to a drain blockage rather than due to a failing septic system are provided

Diagnose Slow or Clogged Drains: 12 step procedure to diagnose & fix a blocked or slow plumbing drain

Here are twelve easy steps to take, in order, to deal with a clogged or slow drain. In the process we'll discover if the problem is only a blocked pipe or if the septic system is at fault. Before digging up the septic system be sure to go through these steps - it may save you some money.

Note: Some of these plumbing drain clog diagnostic steps attend to distinguishing between a drain problem and a septic system problem.

If your building is connected to a sewer system rather than a private septic system, the text in these steps that identifies the location of a problem in drain lines outside the building still apply, as your building sewer line connection between building and sewer main may be in trouble.

Of course other features, such as a flooded or failed septic drainfield won't pertain directly, though indeed a municipal sewer can also back up into a building.

  1. Check several building plumbing fixtures: Refining the above procedure, if the main building drain is clogged, or if the on-site waste disposal system is blocked, fixtures on upper floors in a building may appear to drain normally, while fixtures on lower floors or at the lowest level in the building may not drain at all, or may even overflow back into the building when upper floor fixtures are operated.

    If the problem is just at a toilet see TOILET REPAIR GUIDE for how to diagnose and repair toilet flush, fill, noise, drain, odor, sound, running problems of all kinds.
  2. Check the history of the slow drain problem: if the drain has always been slow, we suspect a plumbing problem such as improper venting, a drain installation error, or a problem with the individual fixture since the day it was installed (such as a poor flushing toilet).

    If the drain used to work but has become slow, we suspect a plumbing drain/waste/vent system blockage has developed, or if the building is connected to a private septic system, that could be failing or blocked.
  3. Sink trap parts How to Try to clear A Blocked Plumbing Drain by Yourself

    There are some simple do-it-yourself drain clearing steps that you may want to try before going further in your investigation or hiring of an expert. The four drain clearing methods listed below are discussed in detail at BLOCKED DRAIN REPAIR METHODS.

    Clear a blocked sink trap: before messing with snakes, wires, plungers, and plumbers, if the blockage is at a single sink or tub trap look into the trap with a flashlight.

    Use a toilet plunger to clear a simple blocked drain.

    Use a plumbing snake to clear a blocked drain

    Use a kinetic water ram [buy at Amazon.com] to clear a blocked drain

    See BLOCKED DRAIN REPAIR METHODS for details of these do-it-yourself plumbing drain cleaning methods.

  4. Call a professional plumber to clean individual fixture drain: A reasonable approach at this point is to call a plumber specializing in drain cleaning. By opening and attempting to clean the building drain or fixture drains, an experienced plumber can determine if the problem is with the building DWV system (drain waste vent) or if it's an outside problem. But before calling the plumber here are the simple do it yourself basics for clearing a clogged building drain. If these work you may be back in business.

    If the drain clearing effort is unsuccessful, you will have paid the plumber for his/her time and also you should ask for that expert's diagnostic assistance. If the drain problem is more than a simple intermittent blockage, what is the problem?
  5. Roof inspection of plumbing vent (C) Daniel FriedmanCheck the building drain-vent system: if there is not an obvious drain blockage, and if drains are slow, particularly if you hear a "gurgling" sound at fixtures during draining, I'd suspect that the building vent system is incomplete, improperly installed, or has become blocked (perhaps by an animal or an insect nest, or in northern climates, by snow if the above-roof extension is too short, or by ice if the vent is too small in diameter - rising steam condenses and freezes in the outside portion of the vent).

    If the drain problems occur only in freezing weather or when there is heavy snow, I'd suspect these latter defects.

    If you hear a gurgling at the sink when the toilet is flushed this might be the case. Have a plumber inspect and test the vent system. Blocked vents do not usually cause drain backup but they will cause slow draining.

    Also see Drain Noises: may indicate defective or clogged plumbing: how to diagnose and cure drain sounds, and
    Sewage Odors in Wet or Cold Weather - Septic Odors or Sewage Odor Diagnosis & Repair Guide for diagnosing and eliminating cold weather sewer gas odors.
  6. If the in-building DWV piping is not blocked, and if the drain line between the building and septic tank (or equivalent component such as a cesspool) is not blocked, and if in-building drains are slow or blocked, the problem is most-likely in the on-site waste disposal system.
  7. Even if the problem appears to be "outside" of the building, you still have not determined whether the problem there is a blocked or damaged drain line or a more extensive failure of the onsite waste disposal system. This is a very important distinction. Un-clogging a drain line, or excavating and repairing a crushed or broken drain line outside the building is typically a much less costly repair than replacement of a septic tank, drain field, or seepage system.
  8. If the problem is in the on-site waste disposal system, additional inspection and testing are needed to determine the nature of the failure. Again, a blocked drain line exiting a septic tank, or a failure in the distribution box (connecting the septic tank to the network of drainfield lines, seepage pits or galleys) the repair needed may be local and modest in expense.
  9. Snake (clean) the building drain between house and septic tank: this will check for obstructions, roots, and collapse in the line between house and tank and will also, if you don't already know, determine the probable distance from the house to the septic tank.

    If you're seeing recurrent blockages in a buried waste line, I'd suspect that it may be improperly sloped, or that the pipe may have been partly broken by vehicle traffic, or that it's partly blocked by a tree root or debris. An experienced drain cleaning professional can often tell by the "feel" of the plumbing snake just what kind of obstruction has been encountered.
  10. Open and inspect the septic tank: if the intake or outlet drains from the tank are blocked because of floating scum or high sludge in the tank, the tank needs to be cleaned. Call a septic tank pumping company. But beware: if scum or sludge levels in the tank were excessive, you've been pushing solids into the absorption system and you may have reduced the remaining life of that component. If the baffles are damaged they should be replaced.

    If your building is connected to a municipal sewer (not to a private septic system) there may be a blockage in or damage to the sewer line between your building and the sewer main. You might also check with your local water and sewer municipal department to be sure that there is not a temporary stoppage in the main sewer. The sewer line between an private building and the public sewer main is the responsibility of the property owner to maintain and repair, but you may need permission from your municipality before you can excavate or make other repairs.
  11. Find and inspect the distribution box: if the tank is clear and its inlet and outlet not blocked, and if drains are backing up in the house I'd expect the liquid level in the tank to be abnormally high and I'd be looking for a blockage in the absorption system, or a soil absorption system failure.

    The distribution box (or boxes) connect the tank outlet to multiple leach lines, seepage pits, or other soil absorption system(s) (if more than one is present). Look in the D-box. If the box has been flooding and all of the outlets from it are equally distributing effluent, the absorption system is blocked or in failure.

    But if the box is tipped or otherwise misadjusted so that effluent is not being distributed evenly across the absorption system sub components, that defect should be corrected. However I would not expect a tipped D-box to lead to drain backup in the building.

Also see CAMPING & EMERGENCY TOILETS and also see TOILET ALTERNATIVES for a discussion of camping toilets, chemical toilets, emergency-use toilets, waterless toilets, graywater systems, composting toilets, home health care toilets, incinerating toilets, outhouses, and latrines.


Continue reading at BLOCKED DRAIN REPAIR METHODS or select a topic from the More Reading links or topic ARTICLE INDEX shown below.


Suggested citation for this web page

CLOGGED DRAIN DIAGNOSIS & REPAIR at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

More Reading

Green link shows where you are in this article series.


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Technical Reviewers & References

Publisher's Google+ Page by Daniel Friedman

Click to Show or Hide Citations & References