This is for a VERY knowleagble plumbers-Please help!!!

Baltimore, MD(Zone 7a)

I am desperate!!! Long explanation follows--bear with me.....

I have a 4-level split house in a Development. Level one and two are above ground (Kitchen, LR and DR. and 3 BR's)
Level 3 is Club Room, an extra bedroom (used to be my Hubby's "office"), a small full bath, and the door out
to my yard. This level is about 50% underground.

Level 4 is the lowest. It was my Ex.'s Shop. This level also has my Laundry room, the furnace and Water Heater
and a small storage area. This level is about 75%-80% underground.
So much for geography......

Here is the issue I need help with. It is the Bathroom on level 3. Seldom used....
So many times--randomly--it emits sewer gasses that stink up my whole lower level.
When i do flush the toilet down there--there is a definite "bubble" that comes up as it flushes.

I work at a HD. Once I was talking to a customer and he said he owns a lot of rental homes.
I explained to him about the sewer stink and asked him if he would know what it is caused by.
He said--"Sure!--I have dealt with the same issues"....I was SOOO happy to hear that....Hmmm...

He asked me if it was the lowest level toilet in my house. I said--"Yes"...
Then he said that that may be the cause of my sewer smell problems--as any toilets I flush (there are two more upstairs)
may be sucking out all the water from the lower traps and causing the gasses to emanate.
He suggested that--every time anyone flushes the lowest level toilet--I should run water in the sink as well as in the tub
to allow water to re-fill the traps. So--I have been trying to follow this advice--except--no one ever uses the lower BR.+
Would this apply to me flushing the main toilet upstairs as well???

Still--especially right now---no matter how much water I run in the lower sink and the tub--the Sewer gas smell permeates....
It is really disgusting!!! I run the exhaust fan down in this bathroom. I run the water in the sink and the tub to try to get rid of it--
sometimes it helps--and sometimes it does not. It is rather random. Moastly--this is an unused BR.

--Should I contact the County's Sewer service and ask them what to do? I can imagine they would not know.
--If I called out a Plumber--it would cost me mega-$$$$. Can't afford that!
--PLEASE--if any of you out there in DG Land are serious plumbers, what advice would you have for me?????

FYI--Al the walls in all the levels of my house are finished. There is NO bare studding--everything is "done"....
The Sewer clean-out traps are behind walls--but I do know where they are. It would be hard to get to them.

Do any of you plumbers have any ideas what I could do--or why this is happening--almost every day?????

Ask me any questions you want to. If I know the answer--I will reply.

Thank you so very much! Gita

Missouri City, TX

Sounds like the vent pipes from that commode may be plugged. It should vent through the roof, but may have been connected to another (which is now against code). It probably has its own, since you only notice the odor when the commode is used.

Since it is not used often, there may be a bird or squirrel nest in thet vent, or spider web that has been filled with debris that does not allow the sewer gases to escape. If you can get on the roof and locate the proper vent, it can be "snaked" or simply use a water hose to "flush" the vent - the debris should go into the sewer line.

Baltimore, MD(Zone 7a)

Bubba---Thank you for your suggestions.

I have 3 bathrooms in my house. I think I can figure out which vent goes with which one.

The house came with 2 BR's. The lower one--(the 3rd.) was added later when my DH built the club room into
a totally self-sufficient "apartment". Full bath included.

The main Clean Outs are all behind finished walls. I DO know where they are. Would be $$$$$$ to ream them!

Do you think that this is an issue of the vents being clogged up--OR--more that the main
sewer lines being clogged up???

I can have the County Roto-Root the main line --BUT--ONLY from the "clean out" on my lawn --that sticks above my lawn-
to the main Sewer line under the road.
BTW--the Clean-Out It is totally buried under my lawn--and will need to be "found" one more time.
The lawn grasses just seem to gobble it up--as I have a Mulcher lawn Mower.
I can give the location within a couple of square feet. Will call them.

NOW--A question:
IF the roof-vents are clogged up---then why does running water in the sink and tub (to fill up the "traps") alleviate
this gas smell now and then??? NOT all the time??????????.
Again--this Bath Room is NOT used at all in my regular life here. I use the upper level one.
SO??? Does the trap really dry up and allow the sewer gasses to come into the house?

When the stink is so VERY obvious--I flush the lower toilet--running the vanity sink and the tub faucet at the same time
to keep the "traps" filled with water as the man told me to do long ago.
Seems to work sometimes--but, then again--not all that much.

I am beyond frustrated--as this has been going on for several years!!!!


Baltimore, MD(Zone 7a)

I need more input on this problem---Please! More opinions.....

My gut feeling is that it has something to do with the underground Sewer lines.


Missouri City, TX

If the trap dries out, sewer gasses will vent through the trap in addition to the vent, but if the vent is plugged, ALL the gases will vent through the trap.

We have a shower that we do not use, so about every month we pour some water into the drain - then - pour in a couple of tablespoons of cooking oil - that prevents the water from evaporating.

I would check the vent first - that is the easiest and cheapest.

Baltimore, MD(Zone 7a)


This bathroom was added long after we moved in. Not sure if there is a vent on the roof from it????
I only see 2 vents on my roof....from the 2 BR's that came with the house...
Have to ask my EX--he is the one who built everything down there.

Thanks again. What you say makes sense,,,,
Interesting about the oil....Any veg. oil? Does it not clog up the pipes?
Lke--i never pour any oil of any kind in my kitchen sink...

Will have to find a young man (my neighbor???) to climb up on my roof and check.
IF there is a clog--then can it just be poked down into the depths of the vent?
Where will it end up???

Thanks, Gita

Missouri City, TX

Any debris that is knocked loose will fall into the sewer line, so running some water after the vent cleaning would be a good idea.

As for the oil - any kitchen cooking oil will work, but DO NOT use a solid like lard, Crisco, or butter.

Baltimore, MD(Zone 7a)


Thanks again. I got it re the oil....NO lard....:o)

I really do not think this bathroom has a roof vent.
Waiting to hear from my EX--but it has been close to 40 years that he built all the club room.
He may not remember either. We are both "old foggies".....

If there is NO roof vent--then what???????????????? Gita

Missouri City, TX

Opps - no vent is a code violation and a health hazard. It could have been connected to an existing vent with a wye provided it was installed correctly: with the angle going up, not down. A tee connection would have been incorrect, but might allow venting, but would not allow "snaking" to clean it out - you are not going to get a snake to turn 90 degrees.

As for being an old foggie - me too!

Powder Springs, GA(Zone 7b)

I think Bubba is correct. I saw a similar problem on This Old House years ago. It was indeed a clogged vent on some newer home but I think all the commodes were connected to the same vent pipe but only the top floor was an issue and it was more about flushing than gases. After cleaning out the vent (leaves or dead squirrel) the plumber put on a vent cap to keep debris and rodents out and gases flowing. Problem solved.

You should see the venting problems in other countries. At the vacation lodge we stayed at in Belize it appeared the sink and shower vented for each other so if we ran water in both at the same time then water would back up in both instead of draining. I think they used the local handyman to do their plumbing too.

Deep East Texas, TX(Zone 8a)

Reading thru this older thread and I wonder if you have had any success?

A friend here does roofing and says he sees lots of things plugging the vents to cause this odor. He also sees people vent their plumbing wrong which allows the sewer gas to leak into the house. I'd guess this is the case.

Also, yes, it is common for the trap to dry out in sinks and baths that aren't used but not the commode. Flushing the commode shouldn't change the odor. Our spare bath traps will dry from no use but we are on septic/greywater so I don't use oil. I use vinegar periodically which also eats odor.

Hoping you have found the problem....

Baltimore, MD(Zone 7a)


Well--I had to re-read all the entries to remind myself what was written.

I had someone walk up on the roof and look down the vents. There was nothing there.
I have not used the oil--just seems the wrong thing to do.

BTW--As the weather cooled in the fall and now it is winter--I have never smelled that odor again.
Seems to be a hot weather thing only. Does that tell pint to anything interesting????

Not much else to report....Gita

Missouri City, TX

Just an FYI about venting other than plumbing:

The house we bought (and are reconstructing from the inside out) had several bathroom exhaust fans venting into the attic space just sort of aimed at the roof turbine - wrong!! - should have vented completely outside through the roof.

Baltimore, MD(Zone 7a)


All three of my bathrooms have vents that go outside. NOT through the roof! Heavens!
Two are right outside through the siding (the ones that came with the house).
One is under the overhang in front of the house. Kind of hidden....This one is the basement bathroom.

I am OK on all the counts here! Gita

Baltimore, MD(Zone 7a)

Just re-read this whole Thread. It was great to refresh my memory on all that
was written, asked, and answered..

Now that the temps are again in the 80's and getting to the 90's--the odor is
once again present.

I work at a Home depot--and have asked a couple plumbers for advice--
and they all seem to think that the trap (like an upside down below sink trap) does
dry out and needs to be refilled by running water after the use of the toilet.
I do it now as a force of habit.
BUT--the sewer gas odor is there--even if I have not used that bathroom.
The trap either dries up by itself or it is caused by others in the next house
using their toilet???Does it not all go into the main sewer pipe eventually?
The one under the road???

Running water in the sink and tub after I flush does stop it for a while.

This bathroom shares a wall with the under-the-stairs space next to it.
I use this space to store coolers and big pots, etc.
SO--the sewer odor permeates this space as well--which could well be
from the sewer lines drying up. That makes the most sense to me.

Realistically--I cannot imagine calling anyone to check out the sewer connections.

I CAN call the County and they will snake the main sewer line from the clean out
on my front lawn into the main sewer under the road.

If this were full of roots--would that contribute to the odor through the sewer lines?

I know we have hashed this over and over--but maybe someone new can
think of a new angle to this. I cannot afford any major digs or repairs.

My house is now 47 years old--if that helps.... It is a 4-level split. The lowest bathroom
is on level #3. Seldom used...
Level #4 is 80% underground and has the Shop, the laundry area. and storage.

All vents are roofing OK as far as I know. Thanks, Gita

Missouri City, TX

I do not have a sewer gas issue, but we have a whirlpool tub that we don't use, so I have to refresh the p-trap about once a year. By adding about a tablespoon of liquid vegetable oil, the evaporation is really slowed down and does not cause a problem.

Not sure if this would help with your issue, but it is another option.

Baltimore, MD(Zone 7a)


You mentioned this in the discussions above.
SO? I will try it. WHERE do you pour the vegetable oil into?
Sink? Tub? Toilet?

There is something new too....I am hearing a noise I will try to describe.
I only hear it in the lower bathroom. If I stay in there--I would say I hear it every
2-3 minutes.
It is a dulled, metallic sound--and goes like Bum-Boom. (short and longer)
The sound sounds like if you had a rubber mallet and were hitting
some heavy metal object with it. Such as an all metal tub?
It is muted and does nor resonate...but I'm sure it comes from something metal.

Since all sewer pipes are metal--what would cause this?

Missouri City, TX

I would pour the oil into any p-trap that is not frequently used after filling it with water.

If you try running water into all the traps, then flushing, you might b able to hear which trap is being siphoned dry. It will be very subtle, but should sound like it is draining. Might require an acute hearing assistant at each trap.

I have no idea what the metallic sound if from.

It might be worth having the waste line camera inspected. Be sure to get estimates before hiring a plumbing service that has the equipment and expertise to perform the inspection.

Baltimore, MD(Zone 7a)


Are you saying that the Tub, the Sink, and the toilet each have their own
SO--I run water into the sink and the tub. The toilet is already full of water.
Then--I flush the toilet and listen for the draining sounds.
I would say the least used one in this bathroom is the tub. I use the sink now and then
--as well as the toilet, if i am outside in garden--this is then the closest one.

I have a couple of Stethoscopes--I could try putting them in my ears and listening....

SO! If I can ID which trap is still draining--then what?????

Thanks, Gita

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