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Due to the tremendous amount of feedback we’ve received on this section of the site we’ve decided to start another article showing some of the basement odor questions we get get via email. We’ve attempted to problem solve as best we can over the internet. Here is a request, from us, if you have an issue that can be clarified with a few pictures send those over with an email. I will ask for your permission to post the questions and answers before publishing. Thanks Keith and Al for the questions.

Keith : “I just have a question.  What would be the cause of sanitary waste dumping into a sump pump pit that is only used for removing ground water?  My house doesn’t have a sewage ejector.  The sanitary waste piping connects directly to the town sanitary system.  Also, the sanitary waste is dumping into the pit on dry or raining days.”

TPI : First of all thanks for contacting us. I’d be glad to help. I have a few questions for you before I give you an answer.

1) Are you sure no other plumbing fixtures dump into that pit? i.e. laundry tub, shower drain, basement bath etc.?

2) if no other plumbing fixtures are draining into the sump pit then you most likely have a sewer line break somewhere. Just because everything is draining properly does not mean you don’t have a break.

3) to determine whether or not a sewer line break is the problem, you need to do some dye testing. You can call in a professional plumber or you can look for some plumbing trace dye on-line. The most popular trace dye colors for plumbing are florescent yellow/green or blue. You can use food coloring but it usually dilutes too quickly to be very affective. So you’ve got the dye so what do you do with it? Fill up a bathtub and put some dye powder or tablets in the water, put a couple tablets in your toilets then proceed to drain and flush away. Continue to run water, if you have a waste line break the dye will eventually make it’s way back to your sump pit. It may take an hour or so but it will show up.

Hope this helps.

Sewer Smell in the BasementKeith : “Thank you TPI for your reply. Nothing else drains into the sump pit.  It is strictly used for ground water (drain tiles) in the basement.  I will try the dye, but I feel it will be an expensive job.  I was told last year that our main sewer (front lawn) is clay tile and tree roots are growing through it.  So to replace it won’t be cheap.”

TPI : The dye testing won’t be expensive. If you can wait a few days I can drop some tablets in the mail for you and you can do it yourself. Just have someone downstairs with a flashlight checking the water coming in the pit. The sewer repair can fluctuate wildly depending on where you live. You can find a dependable contractor to do  your project for 3K to 4K. For a union contractor that price is a little low. Again depending on where you live you might be able to find some out of work plumbers willing to work for ** to ** bucks per hour. Gosh knows there are plenty where I’m from. Let me know if I can help you in any way. See ya.

Keith : “Thanks again, TPI.  I didn’t mean the dye test would be expensive.  I meant repairing/replacing the sewer pipe would.  I am going to have a plumber snake the sewer pipe, hopefully that will take care of the problem (temporarily).

Yes, the tablets would be fine.  What is the cost?” (We are providing those dye tabs free of charge)

Most likely this is a house sewer main that is cracked by settling of tree roots. The waste water is seeping into the soil and making it’s way back to the sump pit, hence the smell.

Here is another email we received:

Al : “Recently moved into a 20 yr old home with a septic system. When running the central AC, an overpowering septic smell builds up in the basement. The furnace blower runs on the highest setting when the AC is on and seems to create negative pressure in the basement which then seems to pull in the septic gas. The house was vacant 1 yr prior to our move-in. Have checked all the traps and floor drains: wet & no smell. Confirmed the stink pipe is clear by running garden hose water down in. Also cleaned the AC coils, trap & drain lines, and have eliminated bacteria, animals, mold, etc. in the HVAC as the problem. There is no smell unless the HVAC blower is running on HI. The smell appears to originate in the horizontal run of the septic vent pipe in the basement joists. Does not appear to be coming from the ejector pit although planning to replace the seal as part of the process. Changing the AC blower from Hi to Med and providing additional air paths to the basement have temporarily allowed operation of the AC.

Please advise best method to track the source/solve the problem from here.

Is smoke testing a good method?
Am new to owning a septic system and my ignorance is profound and deep. Any help greatly appreciated.”


TPI : Hey Al I’m glad you found us. You’ve done quite a bit of the trouble shooting yourself, am I too vain to thing that you followed our trouble shooting guide? I think you have a break somewhere on the run of vent piping and a smoke test works well. I would start out with a peppermint test first. Smoke can be messy. Have you had your septic system pumped out/cleaned? Let me know.

Al : “Thank you for the quick reply.


Just found your site this morning. All trouble-shooting done by yours truly to-date came from web searching and talking to plumbers. Wish I had found your site sooner.” (We know this is a shameless plug but he wrote it so we’re publishing it. Thanks Al).


“Septic system was pumped in April by the previous owner as a condition of the sale. I also talked to the individual that performed the pre-sale inspection (external system only) and he did not find anything awry during his inspection


“What is a peppermint test?”


A new wrinkle as of today: I have boosted the HVAC blower back-up to HI and turned on the AC. After  1.5 hours of running, no smell. Not sure to be relieved or greatly frustrated.”

TPI : A peppermint test is used to determine breaks in vent piping much like a smoke test would. Go to the local grocery store pick up a bottle of the “Oil of Peppermint”. Go on top of the roof (be Careful) and drop several drops down your vent line. Be careful not get a whiff of the peppermint it messes up your sense of smell. You can go down stairs and see if you smell the peppermint. If you do you know you have a vent break.

Al : “Relative to having no smell today, I did pour water down the garage floor drains yesterday. The house had been vacant for a year prior to our move-in and the garage drain traps were probably dry. Puzzled that this could be the source but the original builder listed this as one item to check.

“We have run the AC on full blower speed a number of times today and no smell yet.”

“Fingers are crossed to point of being painful”

Thanks again guys and thanks to all of our readers for the great response.





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