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Stehvi 01-01-2007 11:11 AM

Sewage odor in basement when plumbing used
Over the last year a sewage odor is in the basement only when the plumbing is used. When the washing machine(located in the basement) is used the odor is tremendous for about 15 minutes. If the toliet or shower (on the first and second floor)is used it is just a slight odor for a few moments. The higher the volume of water the worse the odor is. The odor is not there at any other time.

I made sure all the traps are full of water. I had 1/2 of the plumbing in the basement replaced thinking there was a gas leak in one of the seals. I had a camera run out about 20 feet in the sewage line(line is about 40 feet) to the holding tanks. The line looks great. I am at a loss. The house is 9 years old with only 2 people living there.

I want to finish the basemnet but not until this odor is taken care of. The plumber who relpaced the plumbing is at a loss. He replaced the pipes and seals that seemed necessary. Any advice what the next step is

jpplumber 01-01-2007 11:36 AM

Generally odors come from the wax seals gone bad under the toilet, dry traps as you have mentioned or the start of sewer backups forceing air back into the house, and lastly disconnected (or holes in plastic pipes from rodents) or cracked vent pipes in the walls (or under the floor if you have a crawl space. I don't know what or why half of your plumbing was recommened to be replaced without knowing the cause of the problem, even though odor problems are difficult to diagnose.

Christopher 01-01-2007 01:53 PM


Locate all of the stack vents for your house to make sure that each one penetrates the roof. Typically, each bathroom, kitchen, and laundry has its own vent stack. Two bathrooms back-to-back may share a vent stack/stack vent. The average house has 3-4 stack vents on the roof.

I've seen cases where a vent stack terminated between floors, a major code violation.

Venting leaks are discovered by doing a Smoke Test where smoke is pumped down a drain. While it is always my goal to provide a DIY solution, the Smoke Test is best left to a plumber equipped and experienced in this area.


majakdragon 01-01-2007 04:43 PM

Not to be argumentative but, most standard size houses I have worked on have only one (possibly two) vents stacks exiting the house. Most fixtures are tied into the main vent stack.
I agree that it is probably a vent problem. Perhaps the washing machine drain is not vented. When used, it would have a tendancy to suck just enough water out of another trap to cause the odor. I would suggest running the washer on the spin cycle and walking down the whole basement area while it is draining to see if you can't pinpoint where the odor is originating. Traps do not have to be completly drained to allow sewer gases to enter the house.

Stehvi 01-03-2007 05:56 PM

odor in basement when plumbing used
An update on my problem. I have been trying to eliminate the problem step by step. I had the wax seals replaced, traps are filled with water, replaced some piping that was "thought" to maybe have a gas leak. The odor was still there after using the plumbing(espically the washing machine).

Today I had my holding tanks pumped. It has been just about 3 years since the last time. They guy said the tank and it's consistency look great and it was just about 1/2 full.

Now I tried to see if the smell is still there. I ran the washer twice. All I could detect was the faint smell of dirt. NO sewage odor. Now this is either good or bad. Is it possible somehow that the odor was venting back into the house with a 1/2 full tank or am I maybe looking at a crack in the line. Is it possible that the last time I had the system pumped the lid on the the holding tanks were not properly sealed, causing it to vent back in? (If it seems like I am grasping at straws it is because I am at my wits end.)

The line is about 40 feet. We had the plumber check when he was here and we know the first 20 feet is fine.

Hallelujah the smell is gone but this seems to easy. Is it too good to be true????

jpplumber 01-04-2007 07:30 AM


Venting leaks are discovered by doing a Smoke Test where smoke is pumped down a drain. While it is always my goal to provide a DIY solution, the Smoke Test is best left to a plumber equipped and experienced in this area.

This is the best suggestion if you really want to find out.

majakdragon 01-04-2007 08:10 AM

Stehvi, for the odor to get inside the house, it needs an entrance. Since the tank is outside, the smell has to be coming from the piping. With everything you have done so far, it seems that you MAY have a crack in a drain line. In your previous posts, you have not mentioned the vent stack (the pipe that goes through the roof) being checked. If it is clogged (birds nests, leaves etc) whenever a drain is used, the possibility of traps being unsealed is possible.

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