PHOTO of sewage contamination sludge on the floor in a basement from a sewer line backupPriority Response to Sewage Backup, FAQs
Q&A on What to Do for Septic or Sewer Backup

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Sewage or septic system backup response Q&A:

Answers to frequently-asked questions about what to do if your home or building has had a sewage spill or septic system backup into, below, or around the structure.

This article series explains just what to do in response to a septic or sewer backup into or even outside and around a building or in response to building flooding: this article explains how to respond to septic system or sewer backups in a building.

We explain the inspection, cleanup and other steps necessary to sanitize a building that has suffered flooding or sewage-contaminated backups as well as steps to return the building drain, waste, vent system to operation.

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What to do When the Septic or Sewer System Backs Up At or In a Building

Evidence of sewage backup outdoors near a drain line cleanout (C) PG

Questions & answers posted originally at this article SEWAGE BACKUP, WHAT TO DO

[Click any image for an enlarged, detailed version]

Watch out: sewage spills contain contaminants that can cause serious illness or disease. Disease causing agents in raw sewage include bacteria, fungi, parasites, and viruses and can cause serious illnesses including Hepatitis A.

On 2017-06-10 by (mod) re: what to do about grey wastewater coming up underneath the house


A broken sewer pipe or a failed septic system that is backing-up are likely causes. You mom needs help from a plumber.

Keep in mind that sewage under a home is a health hazard. Following the repair and basic cleanup some sanitizing and then perhaps putting down of a 6 mil plastic barrier might help.

On 2017-06-10 13:35:45.495597 by Brenda

My mom lives in an older house she has grey water coming up underneath of it her house is starting to stink on the inside terribly what could be the problem

On 2017-03-26 by (mod) re: is it ok to stay in a home that has raw sewage in the crawl area?

James you asked and we replied at CRAWL SPACE SAFETY ADVICE

On 2017-03-26 by James T

Landlord is evicting my family and I do too that sewage spill in the crawl space they said that it is in habitable and unsafe and that we have to leave

Are sewer line broke in the crawl space under the house and sewage leak under the house. Do we have to move out for cleanup to be completed or can we stay in the home

On 2017-02-09 by (mod) re: what could have caused sewage to com eout of the basement toilet?

Possibly your sewer main or septic tank is backing up into your building.

When the building main sewer line is blocked or when a septic tank or system is blocked, and when an upstairs plumbing fixture is run, that water enters the upper portions of the building drain system. When the main drain is blocked and wastewater cannot exit the building the waste from above creates a pressure in the drain system that will force wastewater or sewage out of any opening that is below the upper floor toilet, sink or other fixture.

That means that flushing a second floor toilet into a blocked drain may cause sewage to pour out of a lower floor toilet or enter a tub or shower through its drain.

On 2017-02-09 by Anonymous

My badement flooded with sewage. It appears that it all exploded out of the downstairs toilet and out into the downstairs kitchen and laundry area.

We did not use enough water the last 48 hours to cause that much water(sewage) to spill out everywhere .

What could have caused this ?

Also everything over flowed in the middle of the night , I found it all like this in the morning

On 2017-01-24 by Linda

have a clogged toilet and had it snaked out 3 days in a row by a plumber, after a day of usage it clogs again, could this be my septic field, no other drains are clogged

On 2016-11-07 by Randa Daugherty

I recently had a sewer leak where my drains all were leaked under the house. It smells strong of sewage if I turn on the heart or account unit, and the landlord wants to pour 5 gallons of bleach under the house to "kill ne mold". There is a pool of blackwater there I feel this is not a safe way to cleanup the spill. What do I do?

On 2016-07-24 by (mod) re: after a forest fire our septic contents backed up into a toilet

Interesting question, anon. I don't know. If plastic sewer pipes were overheated and melted or collapsed by fire that could certainly give a backup condition; that combined with water entering the system from fire fighting or from rainfall might combine to push sewage back into the building.

I suggest exploring the sewer piping, perhaps by a sewer line camera, to find where it's blocked or damaged.

On 2016-07-24 by Anonymous

My vacation house was in a recent forest fire. Minimal fire damage to house but complete burn up of trees and all ground cover. We find septic system contents backed up full in the toilet, but not overflowed it. We were at the house 2 weeks before the fire and had no problems with the toilet flushing etc. Was it the heat that caused this to happen ?

On 2016-07-16 by (mod) re: how to get smell out of the drains of a 5th wheel trailer that is in daily use


Search InspectApedia for SANITIZE the WATER HEATER or SANITIZE the WATER SOFTENER to see general approaches and concentration of bleach; typically you can mix a proper solution, run it through the system, let it sit 24 hours, flush it out.

On 2016-07-16 by T

How do you get the smell out of the pipes of a septic tank in a 5tb wheel trailer that we use daily? We have tried all the cleaning items you get at an RV store and its not helping! Any suggestions ?

On 2016-06-12 by (mod) re: sewage entered the slop sink - could that cause a mold problem in the AC system?


I'm assuming you're talking about the condensate drain for your A/C system? If so, only if the A/C drain was under sewage would it be particuarly worrisome.

If you are asking if there was airborne bacterial contamination in the HVAC system, that's possible; you might want to swab test your air handler and duct system for bacterial contaminants.

On 2016-06-12 by KST

I had a sewer main break in the street. Sewage was backing up in my slop sink for weeks and slowly draining.

It never overflowed into my basement. Is there a possibility that my central AC unit was compromised since it is across from my slop sink? Possible mold contamination?

On 2016-06-06 by (mod)

In the article text above you'll find live links for key articles are CAPITALIZED for example use the InspectApedia search box to find these articles:

at SEWAGE CLEANUP STANDARDS we describe in more detail the steps in removing sewage & disinfecting & cleaning a building interior after a sewage backup or spill, and for a better understanding of what a competent professional will do to clean up sewage spill contamination in a building we list articles [PDF format] that give detailed standards and procedures for sewage cleanup in or even outside of buildings.

Crawlspaces & basements:
at CRAWL SPACE SEWAGE CLEANUP we describe procedures for cleaning up a sewage spill inside or around buildings (not just for crawl spaces).

Flooded buildings: for extensive building flooding,
at FLOOD DAMAGE CLEANUP & REPAIR GUIDE we list the steps needed for repairing a flooded home.

On 2016-06-06 by Anonymous

How do you get the smell out of your house after a sewer back up

On 2016-05-08 by (mod)

Anon: so sorry but I don't understand the question as you've just posted it. It sounds to me as if you had a sewage backup that needs clean-up including disinfection of all of the affected areas including your HVAC ducts. If the ducts contain interior insulation, it will probably be less expensive to replace them entirely than to try to remove insulation, clean the duct interior and then re-insulate it.

On 2016-05-07 by Anonymous

Did not answer my question. The sewage back up from the wash machine area and into the bathroom and then into the air ducks that was on the floor. Floor vents that go to the air conditioner.

On 2015-12-13 by (mod) re: home remedy for sewage backup into washing machine?


you'd need professional cleanup if there was an extensive sewer smell througout the floor of your home.

The cause of sewer backup may be a blockage in your own drain or on public sewer there could be a system problem. I don't have enough data about your home to guess.

On 2015-12-07 by Mona

Is there a home remedy?

Sewer water is coming out of the washing machine drain pipe and garbage disposal

On 2015-10-20 by (mod) re: when toilet is flushed pipes gurgle and water comes out of the outdoor sewer line vent


Something is rotten in Denmark: a toilet flush is "blackwater" or sewage; if flushing a toilet is causing anything to happen at a separate "graywater" sytsem then the system is not in fact "separate".

And no sanitary code allows us to dump sewage NOR graywater to the surface.

Yes I'd ask for help from a plumber to sort out what is connected to what and then help from your septic contractor to find out why you're discharging to the surface. I suspect there is a blocked line or a failed septic system.

On 2015-10-19 by Toni Rigby

Had septic emptied but grey water tank seeping through soil leaving huge puddle of water. When toilet is flushed the pipes gurgle and water comes out of the vent outside and spills over leaving it very wet. Should I get a plumber out before or after grey water tank is pumped?

On 2015-09-04 by Anonymous

How to get rid of sewer smell after toilet overflow?

What Makes Septic or Sewer Backup Wastewater Appear on Different Building Floors?

Question: can sewage or septic backups appear on upper building floors due to a bad drain line?

If you have a septic and the line is back pitched from the house to the tanks:

Is it possible for the backup to overflow the basement toilet and the 1st floor toilet? Or is it impossible for the backup to reach the main floor after the basement toilet overflows.

Is it possible for the main floor toilet to overflow and not the basement ?

Thanks in advance for your help, M.L.

Reply: Possible causes of septic or sewage backup

A competent onsite inspection by an expert who is familiar with septic and sewer systems usually finds additional clues that help accurately diagnose a problem with septic piping, backups, failures and overflows into the building. That said, here are some things to consider:

A septic system or a clogged sewer line, or a flooded sewer or septic system can certainly back up into a basement, crawl space, or other lowest floor of a building

A septic system (or even a sewer) draining out at basement level from a muilti-story house would not be expected to back up onto upper floors because it would find exit points first in the basement at toilets or other fixtures, and because it would be unlikely to develop enough pressure to force sewage out onto upper floors.

An exception to the point above would be the case of a building whose main drain is lower than a sewer or septic piping system. Such buildings use a pumping chamber to push wastewater to its destination.

If the septic or sewer pumping system failed and if the necessary check valves were not in place or were defective, sewage could back up to higher levels in the building What would more likely cause both sewage backup into a basement and onto upper floors in a building would be blocked system drains.

Follow-up from reader:

Just further clarification if you don't mind: i had a belly in my pipes and had a back up 3 times, 2 times for sure in the walkout basement and 1 time I believe it went to the floor above the walkout basement. I just wanted to know if that might have been the cause of the other floor or was it just coincidence that this happened during the same time as the other problem. Is it possible that this was the result of the belly in the pipes or just a random occurence ?

Reply: a belly or sag in sewer piping can cause partial and eventual complete drain blockage and sewer backups

Sewer backups may seem to be a random occurrence but in fact if we knew exactly what was going on with the drain, waste, vent system and the local sewer or septic system, there would be no backups attributed to just "chance".

A sag in a drain pipe can, over time, collect sediment, corrosion, and sewage that can lead to an eventual clog and backup. That's why plumbing codes specify that building drain piping should slope continuously with "horizontal" runs sloping at 1/8" to 1/4" per foot.

What can happen is that a partial blockage of a drain line accumulates more and more debris and becomes more and more solidified until a combination of a particularly large "dose" of solid waste, say feces and toilet paper, has trouble making it past the slow or partly blocked area. That in turn can lead to an actual sewer backup.

Question: Testing for illnesses related to sewage backups or sewage contamination: Leptospirosis, Typhoid Fever or Yersiniosis

Approximately 2 months ago I moved into a new house, and 1 week in there was a sewage leak into the backyard. All of the piping needs to be replaced but only a small section has been, so although it is not spilling onto the surface of the yard anymore, I believe it is still leaking into the ground under the surface.

My dog has been very ill since living here (vomiting, diarrhea, and is now developing skin lesions). The tests come up negative for Giardia, but he gets better when on antibiotics. As soon as he is off the antibiotics he relapses and it finally occurred to me this may be due to the fact that the incoming water is contaminated.

He has not been specifically tested for Leptospirosis, Typhoid Fever or Yersiniosis, which I plan on having done today. Is there anything else you feel I should have him tested for?

In regards to the water testing, do you know of a laboratory in the Sacramento, CA area? If so, I would greatly appreciate you providing me with their contact information. Would the Total Coliform test be sufficient, or is there further testing you would recommend?

Thank you in advance for your help. - Best, L.S.


L.S. these are questions to ask your veterinarian and your doctor. Having some experience with Typhoid fever I can mention that our doctor advised that it was very important to be sure that any treatment for Typhoid be continued until the doctor is sure that the treatment has been effective, and thence it is important to avoid re infection. An incomplete treatment for Typhoid, such as failure to complete an effective course of antibiotics, risks leaving behind a antibiotic-resistant strain that could make future treatment still more difficult.

While the physician with whom we consulted, [S.R. SmDA, Nov 2011] is convinced that the only vector for Typhoid fever is from eating [Typhoid strain of salmonella-] contaminated food, we have also read that a secondary vector might be possible via mosquitoes or flies in contact with sewage.

Question: Could an upstairs bathtub drain problem cause a basement septic system to back-up?

(May 7, 2012) Sara Young said:

Could an upstairs convoluted bathtub drain cause a basement septic system to back-up? We had a camera put into our basement vent stack drain line. We then inserted a water hose and all water flowed without any back-ups towards and exiting into our septic system.


Yes Sara or conversely, a blocked sewer line may show up as slow fixture drains in the building.

Question: clog in a septic supply line causes tubs and commodes to overflow?

(Oct 4, 2012) Rie said:

Can a clog in a septic supply line cause tubs and commodes to overflow?


Yes Rie


11/30/2014 Anonymous said:

terrible gas odour in bath room and in back hall behind bathroom. plumber put new adaptor and seal in toilet....smell still there. house is 30 years old. any suggestions please.I'd appreciate your advice, thanks Mary


Anon Perhaps there is a break or leak in the plumbing vent system. Ask your plumber if s/he can test for that. OR there was a sewage leak into the floor/ceiling below the toilet and sewage remains there.


Continue reading at SEWAGE BACKUP, WHAT TO DO or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see SEWAGE CLEANUP STANDARDS - where we describe in more detail the steps in removing sewage & disinfecting & cleaning a building interior after a sewage backup or spill and where we provide documents with still more detail from experts on sewage spill remediation

Or see CLOGGED DRAIN DIAGNOSIS & REPAIR if drains in the building are slow or backing up

Or see CLOGGED DRAIN vs SEPTIC PROBLEM if you think your house drains are not blocked

Or see SEPTIC FAILURE CRITERIA for help in determining if in fact the septic system has failed

Or see these

Septic or Sewer Backup Articles

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SEWAGE BACKUP RESPONSE FAQs at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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