[TonyR]

I have not submitted a question here before but found such useful information I thought I'd give it a try. We have a new home that we moved into 2 months ago and have run up against a very puzzling problem. We have had a bad, intermittent sewage odor at the front of the house since prior to closing. It was so bad at one point the private inspector we hired just prior to closing suspected it could be a dead animal under a pile of rock and rubble that has long since been cleared.
The odor is a sewage odor, or methane related gas odor. We were smelling it early in the mornings, from about 6:00 AM - 9:00 AM, and in the evenings from about 5:00 PM - later but now we are smelling it more in the evenings. We never smell it in the mid afternoon. Our home is in Austin, TX if that helps.
We suspect the odor is methane gas coming from the plumbing vents which are at the top of the house and the gas is filtering down to the front of the house. Not sure if that makes sense, but that is all we can ascertain at this time. This is a 1.5 story house with 2 baths up and 2.5 baths down. The smell is isolated to a general vicinity right near the front door and front side walk when it is present. The strange thing is it does not smell every day, and some days the smell is stronger than other days. We asked the plumbers to come and investigate and they did a "smoke test" to look for any unsuspected leaks in the plumbing vents. In addition they ran a camera servey to look for cracks in the plumbing lines. They told us it was not a plumbing problem as they found nothing unusual. They told us it might be the dirt in the beds at the front of the house, or something perhaps as arcane as buried rotting tree roots in the front beds, however I believe if this were the case it would smell every day throughout the day. We also asked the city to come and investigate to be sure there was nothing happening at the street, as this is city sewer, although we suspected this was not the issue since we never smell the odor close to the street. A few times we have also smelled the odor at the back of the house just off the patio, but only a couple of times in that location. Mainly it is at the front of the house near the front entrance and limited to a very distinct 100 - 150 ft ft radius, which by the way is not far from the plumbing pipes. I have read that Extending the plumbing vents higher on the roof or installing a wind block at the vent tops might help, if in fact the smell is methane gas coming from the plumbing vents. I also read that possibly installing a deflection device (much like an upside down chimney cap) on the tank outlet tee may resolve the smell. We are hoping someone may read this and be able to help us. Our builder is coming to take a look this week but if the smell is not in the air when he is here we are afraid he will be uncertain where to look next, especially since the original plumbing contractor has wiped their hands clean of it and given a clean bill of health report back to the builder.

Please let me know if I can provide any additional information. I'd be glad to. I am so hopeful that all of you out there may be able to help us as the original plumbing contractor has not.

[speedball1]

City sewer or septic tank? Do you live below a hill where you might get downdrafts? It sounds like sewer gas to me no ,matter what the plumbers say. Let me know, Tom

[TonyR]

Tom,

We have city sewer. Interesting thing is we are at the highest point on the street. I did some research today and found that there are several manufacturers who make carbon filters for plumbing vents to eliminate "stinky gas". Do you think this is a hoax or possibly worth a try?

[speedball1]

Carbon filters for a vent that doesn't blow gas out but sucks air in to relieve the vacuum generated by draining water. I think you'd be wasting your money. I could see a filter on a septic tank vent but not on a roof vent. Regards. Tom

[TonyR]

Tom,

We were under the impression that the plumping vent is there to vent the gasses from the caused by the water being pushed into the plumping pipes, which is the way we assumed it should work. Do you think our theory that the sewer gas is coming from the vents is incorrect?

[speedball1]

Tom,

We were under the impression that the plumping vent is there to vent the gasses from the caused by the water being pushed into the plumping pipes, which is the way we assumed it should work. Do you think our theory that the sewer gas is coming from the vents is incorrect?

Let me explain about vents. You are under the impression that a vent expels air when a toilet's flushed or a fixture's drained.
Not so! When something's drained the water going down the pipe sets up a vacume behind it that retards the discharge and attempts to vent through the trap pulling on the water seal lowering it. The vent replaces the vacume caused by the discharge. In other words the discharge pushes air ahead of it while pulling air in behind it. Sooo, Vents pull air in they don't push it out.
A exception to this can happen if the house is situated on a hill where downdrafts can occur. But in all the years I've been out n the field I've only seen this happen once. Regards, Tom

[TonyR]

Tom,
Our property is at the highest point on a hill. It is not a steep hill were we sit at the top, rather a gradual sloping hill where we sit at the highest point.

Would you have any thoughts or suggestions of what we should do next? Where else might this sewer oder be coming from? We are desperate. Our concern is that whatever this is could lead to an underlying larger problem.

Thank you.

[speedball1]

Ok Tony, Let's do some checking. Look down the drain at all the traps. If they're full of water then you should be OK, but if there's almost no water in any of the traps then you could have a vent that's blocked. Also you've tried everything else you might want to consider replacing the wax rings in your toilets. Sewer gas can escape a defective ring yet not leak water when flushed. The wax ring can emit sewer gases from the base of your toilets and you will swear it's coming from the shower/tub drain, lavatory drain etc.
Sewer gases have a way of dulling the olfactory nerve and make detection nasally impossible.
You must realize that smells and weird noises are the hardest to track down when you're on site and just about impossible when you're not.
All I can do is point out likely spots. If you believe you may have a vent problem then a smoke or a peppermint test might help. Regards, Tom

[TonyR]

Tom,

Given that the sewer odor is not on the interior of the house and only the exterior, would replacing the wax rings potentially correct this outside issue?
The original contractor plumbing company did run a smoke test and found nothing unusual. Can you tell us what a peppermint test is?
We understand the difficulty in trouble shooting this one. Given that the smell only appears at the early morning hours or late into the day and evening it's tough to get people here when the odor is actually the strongest.

Tony

[MAXINE COTTON]

Had pipes replaced that go to sewer vent- still smell sewer gases at certains times of the day- mostly at dusk and early evening.

Does not last but about an hour or so.

I have crawl space- could there be some overflow from the sewer under the house?

[raymondvinzant]

Tony
If you are on septic, for every gallon of water you put into the waste system, you have to displace a gallon of air. With a septic tank the water will run down to the septic tank because of pitch and the weight of water, but the air will not. Each septic tank has a tee or a turned down elbow, which sits below the level of the water in the tank. Since the air cannot push past the water seal in the tank, it can only go up and out the roof vent of the house. This is not the case on a house with a city sewer, the air will travel ahead of the water and into the city sewer system. So every time you use the plumbing system, you are pushing sewer gas, which is created in the piping system from waste that is beginning to deteriorate, up to the roof vent. If you have a static air condition, where there is not much wind, the sewer gas, which has the same weight as the outside air, will linger around the house. If the condition is right, a light wind can blow it in the direction of the doors and windows. We had one case where the house had two main vents on the roof, the wind blew across one vent and part of it was diverted into the plumbing system, which then exited from the other vent on the opposite side of the house and carried the sewer gas it picked up from the piping system outside.

By the way, if you are on city sewer, the air pushing in from other homes across the city creates a pressure in the sewer system. This pressure can push sewer gas out the roof of your house. Think about all of the gallons of water put into the city system, which through resistance is pulling and pushing the air ahead of it. The waste in the city system is designed to run at 2' per second. That means the air is also traveling at a similar but slower speed. Under the right conditions it can be forced out your roof vent because the entire neighborhood is tied together. If that is the case, you could install a house sewer trap on the outlet of your house and eliminate the problem. This is done a lot on the east coast. New York requires these traps to prevent sewer gas from one home row house from entering an open window of the next row house.

[Milo Dolezal]

Tony: If there is a Low Atmospheric pressure, the gases from roof vents will not go up but will fall down towards the ground. In the City where I grew up, we used to predict rain by the smell of sewer in the streets. It was pretty accurate...

Also, it may be the location of your house: if you house is located in a place where winds swirl they may also push gases towards the ground and keep it there for while.

Talk to you neighbors about this. Ask them if they are experiencing same problem.

[teralittle]

We have the same problem and only at certain times of day. We have had the city and 3 separate plumbers out and no one can diagnose the issue. The problem did not start until the city did a MS4 "municipal separate storm sewer system." . The city claims no responsibility for the odor, but I have my doubts. I can barely stand it if anyone has an answer please help!!