Sewer gas from septic filling house when washer runs

[Steve Furbish]

I have a 60+ year old ranch that sits on a full basement. I recently had a new septic system installed (last November) when the old homemade system finally failed. The new system is an elgen system with a 1200 gallon tank, divided in the middle, that empties to a small pump tank before it's sent to the Dbox and to the elgen field. About 3 weeks after the new system was installed I started noticing a septic gas smell every time my wife does the laundry. The smell fills the house upstairs and down after the first spin cycle. The drain plumbing is a 3" waste stack that runs from the upstairs toilet down through the cement floor and out to the septic tank. There is a 3" vent stack that runs from just below the upstairs toilet up though the roof. Below the vent is a 2" drain pipe from the upstairs tub and sink (vented with an AAV), a 1.5" drain from the kitchen sink and dishwasher (also vented with an AAV), a 2" drain from the washing machine standpipe (vented with an AAV) and below the cement floor a 3" cast metal drain that handles the downstairs toilet and a closed off shower drain (not vented). I have replaced the wax rings in both toilets and had a plumber in to redo the above mentioned kitchen and bathtub drains. The gas smell persists and I noticed today that the downstairs toilet bubbles up pretty hard when the upstairs toilet is flushed, but there's no gas smell unless we run the washer or take a shower. My plumber leak checked everything above the floor and could not find the problem. We check all of the traps after the washer ran and none were siphoned out. At this point I'm kinda stuck. I was unable to find anyone in my area that does smoke or peppermint testing. Anybody got any ideas for a next step?

 

[Timb39]

Either remove the AAV and run the vents out if you are able to or try replacing the AAV with new one. Lack of air will cause the toilet to bubble. The AAV might be stuck open

 

[Sponsor]

 

[Steve Furbish]

Either remove the AAV and run the vents out if you are able to or try replacing the AAV with new one. Lack of air will cause the toilet to bubble. The AAV might be stuck open

Thanks for the response, but I guess I wasn't very clear. I had the plumber add the AAVs recently to address the sewer gas smell. My wife tells me that the downstairs toilet has been burping like that for some time now. It doesn't overflow so she didn't bother to tell me. Everything in the house is within 5 or 6 feet of the waste stack and three inch roof vent except the clothes washer which is about 10 feet away. The AAVs didn't eliminate the sewer gas odor but they didn't make it worse either. Everything drains fine and and the traps don't lose water from siphoning so I'm suspecting either a partial clog between the house and septic or a cracked pipe somewhere. Nothing leaks so I'm going to try doing a smoke test on my own and if I don't find anything I'll have the plumber come back and snake the underfloor lines in the basement out to the septic tank.

 

[Timb39]

The only reason why the toilet would gurgle is because lack of air or partial clog in line. The sewer gas smell is either a broken line or when using the washer the trap there syphons out. If that’s not happening then hopefully the smoke test works. Fingers crossed. Don’t forget to cap off the vent that goes out for smoke test.

 

[WorthFlorida]

You may need to go to the roof at the vent pipes and check for any obstructions. Birds could have nested inside the pipe or any kind of animal. If not you may need to get the vent stack scoped out looking for any obstructions.

A 60 year old house the vent of main stack is probably cast iron pipe. Look for rust at the joints.

 

[Steve Furbish]

The only reason why the toilet would gurgle is because lack of air or partial clog in line. The sewer gas smell is either a broken line or when using the washer the trap there syphons out. If that’s not happening then hopefully the smoke test works. Fingers crossed. Don’t forget to cap off the vent that goes out for smoke test.

That's what my plumber said, but the toilet and drains all flow well and the downstairs one was recently removed for a new wax seal. While it was off I flushed the line by pouring a six gallon stock bucket down through the 4 inch cast pipe that runs under the concrete floor and there were no signs of obstruction.

 

[Steve Furbish]

You may need to go to the roof at the vent pipes and check for any obstructions. Birds could have nested inside the pipe or any kind of animal. If not you may need to get the vent stack scoped out looking for any obstructions.

A 60 year old house the vent of main stack is probably cast iron pipe. Look for rust at the joints.

When the plumber was here running new pipes he cut the 3" PVC vent line near the waste stack to add a wye. I could look right up through the vent and see sky so it's not clogged. The reason I want to do a smoke test, however, is because the waste stack is that old gray PVC that connects to the cast iron just above the basement floor. I was thinking that when they put in the new septic the 70 ton excavator banging around outside the house may have shaken the stack and broken the glue seal at one or more of the connections on the stack?

 

[Michael Young]

Thanks for the response, but I guess I wasn't very clear. I had the plumber add the AAVs recently to address the sewer gas smell. My wife tells me that the downstairs toilet has been burping like that for some time now. It doesn't overflow so she didn't bother to tell me. Everything in the house is within 5 or 6 feet of the waste stack and three inch roof vent except the clothes washer which is about 10 feet away. The AAVs didn't eliminate the sewer gas odor but they didn't make it worse either. Everything drains fine and and the traps don't lose water from siphoning so I'm suspecting either a partial clog between the house and septic or a cracked pipe somewhere. Nothing leaks so I'm going to try doing a smoke test on my own and if I don't find anything I'll have the plumber come back and snake the underfloor lines in the basement out to the septic tank.

You've got something in your pipes blocking air. When you use a fixture it creates negative pressure. The gurgling you heat in the toilet is where the air-starved pipes (negative pressure) is trying to get air. Negative pressure = you're sucking the air out of the trap(s) because the system is starved of air. If everything is draining, then it is possible a bird built a next; a squirrel found a good place to hide food in your pipe; squirrel might have even got lodged in the pipe and died. If you can easily get up on the roof, take a garden hose and shove the hose down the vents with one of those pressure heads on it. Go ahead and hit every vent. Once you're done. run a little water in every fixture to be sure there is water in the traps. The hose trick flush out wherever is blocking your vent

 

[Ladiesman217]

I have a 60+ year old ranch that sits on a full basement. I recently had a new septic system installed (last November) when the old homemade system finally failed. The new system is an elgen system with a 1200 gallon tank, divided in the middle, that empties to a small pump tank before it's sent to the Dbox and to the elgen field. About 3 weeks after the new system was installed I started noticing a septic gas smell every time my wife does the laundry. The smell fills the house upstairs and down after the first spin cycle. The drain plumbing is a 3" waste stack that runs from the upstairs toilet down through the cement floor and out to the septic tank. There is a 3" vent stack that runs from just below the upstairs toilet up though the roof. Below the vent is a 2" drain pipe from the upstairs tub and sink (vented with an AAV), a 1.5" drain from the kitchen sink and dishwasher (also vented with an AAV), a 2" drain from the washing machine standpipe (vented with an AAV) and below the cement floor a 3" cast metal drain that handles the downstairs toilet and a closed off shower drain (not vented). I have replaced the wax rings in both toilets and had a plumber in to redo the above mentioned kitchen and bathtub drains. The gas smell persists and I noticed today that the downstairs toilet bubbles up pretty hard when the upstairs toilet is flushed, but there's no gas smell unless we run the washer or take a shower. My plumber leak checked everything above the floor and could not find the problem. We check all of the traps after the washer ran and none were siphoned out. At this point I'm kinda stuck. I was unable to find anyone in my area that does smoke or peppermint testing. Anybody got any ideas for a next step?

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