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.

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?

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.

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

FIRST 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.

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.

[Click to enlarge any image]

See TOILET REPAIR GUIDE.

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 just above 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

at CLOGGED DRAIN vs SEPTIC PROBLEM

Diagnose Slow or Clogged Drains: 12 steps 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.
   
   see DISHWASHER DRAIN CLOG DIAGNOSIS for an example of a blockage at a single plumbing fixture or appliance like a dishwasher or washing machine
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. 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.
   

   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
   
   The four drain clearing methods listed below are discussed in detail
   
   at BLOCKED DRAIN REPAIR METHODS we give 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. Check 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 PLUMBING DRAIN NOISE DIAGNOSIS: since plumbing drain noises may indicate defective or clogged plumbing: how to diagnose and cure drain sounds, and
   
   SEWER GAS ODORS in COLD / WET 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.
   
   See USE a POWER SNAKE to CLEAR a BLOCKED DRAIN 
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 you can't find the septic tank see
    
    SEPTIC TANK, HOW TO FIND
    
    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.
    
    See SEPTIC D-BOX INSTALL, LOCATE, REPAIR 
12. Check the septic drainfield for signs of blockage or failure
    
    See details at SEPTIC DRAINFIELD FAILURE DIAGNOSIS 

 

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2021-09-28 by lenny

thankyou, I'll keep you posted

On 2021-09-28 by inspectapedia.com.moderator (mod) - how do i locate where exactly is the blockage at?

@lenny,

It might make sense to First inspect the septic tank if it is easily accessible. If the sewage level is high in the tank than we know that the tank Outlet is blocked where the field has failed.

Don't lean over or try to inspect a septic tank yourself as that could be dangerous.

If the sewage level in the septic tank is normal then the blockage may be in the building drain system.

That's when you would call a plumber to snake the building drain.

On 2021-09-28 by lenny

how do i locate where exactly is the blockage at? do i snake it or do i have my septic pumped?

@inspectapedia.com.moderator, where would the blockage be? everything empty's out of this main drain pipe to the septic

On 2021-09-28 by inspectapedia.com.moderator (mod) - signs of a blocked drain

@lenny,

Sounds like a drain blockage;

On 2021-09-28 by lenny

I just did this: Opened water at the 1st floor points for at least 5 minutes of kitchen sink bathroom sink bathroom tub, and flushed toilet 3 times, water was very slow draining from toilet at this point, still nothing filling into washing machine, but the the mainline pipe was filling as I knocked on the drainpipe I could fill that is was filling up.

At this time I decided to run the washer on the spin cycle for about 30seconds to a minute, stopped the cycle at which water backed into the washer up to at least 6 inches. Now the drain pipe when tapped fills like its very hollow sounding

On 2021-09-27 by inspectapedia.com.moderator (mod) - water backup during washing machine drain cycle

@lenny,

That sounds as if the drain is blocked or a check valve in the drain system has failed.

Does your washer drain into a sump or other pumping system that pumps wastewater to a higher building drain?

On 2021-09-27 by lenny

my washing machine is in the basement, after its final spin it drains the water out, all of a sudden most of that drained water rushes back through the main line and back into the washer. whats the issue

On 2021-06-15 by inspectapedia.com.moderator (mod) - septic odors after new tank installed

@Jeannette,

Something doesn't sound right here.

There are many homes that use a trap at the main drain exit from the building without recurrent clogs there (though it's proper to include a cleanout openig at that house trap).

I would look for a problem with the drain lines themselves - such as an improper pitch or partial blockage, maybe having an inspection by sewer camera.

In any event, sewer gases in the main drain should be vented either outdoors or properly, by the home's plumbing vent system that discharges above roof level.

So also take a look at the diagnostics starting at SEWER GAS ODORS https://inspectapedia.com/septic/Sewer_Gas_Odors.php

On 2021-06-13 by Jeannette

New septic system. Upsized tank from 1000G to 1500G.

Septic gasses started to come into home. Wasn't an issue before. Plumber installed u trap just before line leaves building and after vent. Now u trap blocks up and has to be cleaned every 3 mos or so. Thoughts on how to fix?

On 2021-04-29 by (mod) - drain noise diagnosis

@Anonymous,

You're not supposed to have to know the lingo - that's for InspectApedia to provide - as much as you can tolerate.

Take al look at our description of the causes of noisy gurgling drains at

https://inspectapedia.com/noise_diagnosis/Plumbing_Drain_Noise_Diagnosis.php

PLUMBING DRAIN NOISE DIAGNOSIS - home

that includes a section on GURGLING DRAINS

On 2021-04-29 by Anonymous

@danjoefriedman,

I went up on the roof to inspect for venting blockage and there was nothing that I could see. And from what you are telling me about the sewage eject, we have 2 pipes that drain everything from the house (grey water) directly into like a reservoir in the basement...

which then empties out in every once and a while. I'm sorry if i dont know the lingo ;)
is there any other way to check the vent to see if it is blocked?

On 2021-04-29 by danjoefriedman (mod) - Pumping a septic tank right before the house is inspected is a questionable practice

@erica,

It sounds as if you have a home that uses a sewage eject or pump to pump waste or waste water up to a septic disposal system. It may be that the pumping system is not correctly vented or that it's vent is blocked. That can cause a gurgling sound it drains.

Just a note about your septic system, pumping the septic tank is important for protecting the life of the drainfield but it will never ever actually fix a problem with the drainfield is already failing.

Pumping a septic tank right before the house is inspected is a questionable practice in that it will make it impossible for a septic inspection test to be performed. It may have been an innocent act by a nervous owner but such an act could also cover a failed septic drain field.

On 2021-04-29 by erica

bathtub makes a gurgle sound (no water comes up though) when the pump goes off to empty water out of our house. We have a septic. Just bought the house 6months ago. Septic was cleaned/emptied by old owners in Aug 2020

On 2020-10-06 by (mod) - gurgling noise and dirty water filling toilet tank after flush

Lindsey

It sounds as if you are describing a problem with debris in your water supply system, not a septic system or building drain problem.

That can happen if the level of water in the well drops, or if the well casing is damaged so that crud is leaking into your well;

The leak from the toilet shutoff valve is common as those valves sit for years not being touched.

Sometimes if you CAREFULLY tighten the packing nut - that's the fairly large nut just unerneath the knob that you turn to open or close the valve - the valve stem passes through it - tightening that can stop a leak.

On 2020-08-12 by Lindsey B

So we have a septic system, a "mound system" and we've lived here for 5 years and have never had an issue but we've also never had it pumped out either...and tonight out of nowhere I flushed the toilet and there was this awful sputtering/ gurgling and then more sputtering so I took the back off the toilet and the water is murky with a weird tanish/brownish tinge to it and slot of gross buildup inside the tank

...and the pressure pump?(I think it's called) not the sump pump but the other tank that pumps the water through the house (I think, that's what it does) will not turn off...the toilet fills back up a little slower and not quite as full and the water is murky...

idk what to do..after reading for an. Hour abojt all the possibilities I'm a nervous wreck and i was going to wake up my fiance but now I'm even more nervous bc yikes he's going to be mad.

... we've ways been good about not flushing anything but 2 ply down the toilet and only soft things like wet cereal into the garbage disposal..oh and also when I try to turn the water valve off behind the toilet, water leaks from the valve knob onto the floor....help please!!!

On 2020-05-14 - by (mod) -

I would want more thorough diagnostics, perhaps by sewer line camera so we can see if it's a field failure or a blockage.

On 2020-04-21 by Steve

We had our cement tanks replaced last August. We have noticed the ground being well above the new tank ever since. They told us the leach field was in perfect shape at that time. Now they are saying we need to replace the field We have downstairs toilets not flushing. They mentioned it could be done to doing more laundry, etc with the quarantine? There is no blockage from the house. It's this a necessary did. At first we were told $ 3500.00. Now they are saying $2200.00 What are your thoughts?

On 2020-03-24 1 - by (mod) - toilet only flushes if dump in a bucket of water

Two possible explanations:

1. the "dose" of flush water from the toilet tank itself is smaller than the bucket dose - the bucket dose is giving more flush volume and force

2. the partial clog or blockage is a bit downstream from the toilet itself, so the first flush passes but subsequent ones are slow

On 2020-03-24 by ian

i poured 3 buckets down and went down right away, if blocked why would it go down fast??

On 2020-03-24 - by (mod) -

It sounds like a clogged main drain. Try plunging.

On 2020-03-24 y ian

toilet will flush with bucket of water, but gurgles after. does not flush properly using regular method

On 2019-12-10 - by (mod) - Slow draining septic how can I fix

MCheatom

1. First let's diagnose the problem, with help from a plumber (snake and inspect the drains to locate the clog, blockage, damage), and/or a septic contractor (open and inspect conditions in the septic tank to id abnormal high levels, damaged baffles, need to pump, etc).

2. Then we know what we need to fix: a clogged drain or sagged line can be fixed;

But if the problem is that the drainfield is saturated or not absorbing effluent, you're going to need a new drainfield.

Despite a long interest and reading on magic bullets that claim to "fix" a failed or clogged septic system, both research and feedback from readers confirm that those magic treatments don't work or don't work for long-enough to justify themselves. Those details are at SEPTIC DRAINFIELD RESTORERS? https://inspectapedia.com/septic/Drainfield_Rejuvenation.php

Details of clogged drain diagnosis are on this page.

Basics of diagnosing a slow-draining septic are at SEPTIC DRAINFIELD FAILURE DIAGNOSIS https://inspectapedia.com/septic/Septic_Field_Clogging_Diagnosis.php

Drainfield detailed inspection and diagnosis is at SEPTIC DISPOSAL FIELD CLOGGING INSPECTION https://inspectapedia.com/septic/Soakaway_Bed_Clogging_Failures.php

On 2019-12-0 by M Cheatom

Slow draining septic how can I fix

On 2019-04-19 - by (mod) -

The septic tank may be okay but chances are the drain field is being flooded by surface runoff and back flowing into the septic tank or surface runoff is leaking directly into the septic tank.

Those are conditions that your septic contractor can determine by a closer inspection of the distribution box, the septic tank, and the septic tank Outlet during a tank pump down.

On 2019-04-18 by Teri

Every time the ground of the septic field gets saturated with rain or snow our toilet will not flush. It could be a couple days or almost a week before we are able to flush our toilet again. Does this mean the septic tank - by (mod) -

Sonia

Unfortunately, while it's necessary to maintain a septic system and extend the drainfield life, PUMPING the septic tank has nothing to do with fixing a clogged drain nor will it fix a failed drainfield.

If the septic tank INLET baffle is missing or clogged, THAT could indeed cause solid sewage to back up into the main drain and cause blockages and even sewage overflow indoors.

If the septic tank OUTLET baffle is missing or broken that in turn sends solids ouit into the drainfield, clogging and ruining it.

So you want a thorough inspection by a plumber who can use a sewer line camera to inspect the drain line for damage, blockage, poor slope, or clogs AND who will inspect the septic tank baffles and sewage level to tell you conditions there.

On 2019-03-29 by sonia

washing machine when it drain cycle, water back up. Washing machine in lowest level of house. Toilets drain, Recently had the tank empty,

This has happen before, had it snake from house to septic tank. We were told it is the baffle?, 5yrs ago we put in new drain field . Not sure who to call and not get rip off

On 2018-11-26 - by (mod) -

Lola,

Typically if the plumber running a snake through the lines does not find an obvious blockage then the conclusion is likely to be that the drainfield is in failure and is saturated. It would be smart to inspect the distribution box to see if flooding is consistent there as well.

On 2018-11-25 by Lola

Water from the house is not going into septic. Toilet is. Dug down to the lid of the septic. Shower water filled up on top of tank. A plumber ran electric snake friday. Still have same problem. Snake did not bring out any root particles.

He is returning tuesday. What could possibly be the problem. I called septic people first, they told me to call a plumber. I called them after the plumber and they said they needed to come out now as plumber would not know what he was doing.

I replied that they were the ones that suggested a plumber. I am sticking with the plumber unless he advises to contact septic people. What could this be?

...

Continue reading  at BLOCKED DRAIN REPAIR METHODS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see CLOGGED DRAIN DIAGNOSTIC FAQs - questions and answers about fixing stopped drains, posted originally at the end of this page.

Or see these

Recommended Articles

• CLEANOUTS, PLUMBING DRAIN
• CLOGGED DRAIN DIAGNOSIS & REPAIR
  • BLOCKED DRAIN REPAIR METHODS
  • CLOGGED DRAIN vs SEPTIC PROBLEM
  • CLOGGED DRAIN DIAGNOSTIC CHART
  • FIXTURE vs SYSTEM DRAIN BLOCKAGE
  • KINETIC WATER RAM
  • POWER SNAKE DRAIN MACHINES
• DISHWASHER DRAIN CLOG DIAGNOSIS
• DRAIN & SEWER PIPING - home
• SEPTIC BACKUP PREVENTION
• SEPTIC DISPOSAL FIELD CLOGGING INSPECTION - is the problem blocked drains, bad septic tank, or failed soakaway
• SEWAGE PUMP DAMAGE & REPAIR
• SEWER BACKUP PREVENTION - home
• TOILET REPAIR GUIDE

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.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to PLUMBING SYSTEMS

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