I started getting sewer odors in my house in February 2014. I have lived in my house for 7 years. I never had sewer odors in my house until this February. I have hired four different plumbing companies who have done smoke tests, pressure tests, run water down the vents to make sure they weren't plugged, installed four inch in-line P trap in sewer line and a check valve, and the sewer odors still get through to all the bathrooms. They all have said they can not do anymore. It is a city sewer problem. I have been in touch with the city but all they seem to do is run HS2 tests on a meter and they insist nothing has changed with the city sewer line pressure.Any ideas on who to contact about this? By the way, there are no agencies (government or state) that handle these type of issues. Please, any suggestions would help at this point since I have no dea where or who to go next.

AC,
You can find a leak in your dwv system with a peppermint test. A whole house trap, correctly installed, would not allow sewer gas to pass, unless there was a blockage down stream causing pressurized " burping ".
A sewer pipe camera could help determine if there are any flow issues in your soil & sewer piping.
Sewer gas / odors can enter the house from the roof mounted exit pipe; if this is the case, there are roof vent filters that fit on / over the pipe; they are charcoal activated, and very effective.

Has anyone gone to the basement, when the odor is present in the house, and opened the sewer pipe to sniff and compare odors. There are companies that can collect, and analyze air samples.
There are dozens of other sources of sewer - like odors, have any of these been investigated?

Mike45,Thanks for your response. Two of the four plumbing companies ran the cameras through all the pipes. Pipes were extremely clean according to them. They ran the cameras all the way through to the drop off to the main sewer line. What I get now are sporadic bursts of sewer gas and not a steady gas which indicates to me there is a build up of gas in the sewer lines. I'll try the peppermint test. Thanks.

Mike45,Thanks for your response. Two of the four plumbing companies ran the cameras through all the pipes. Pipes were extremely clean according to them. They ran the cameras all the way through to the drop off to the main sewer line. What I get now are sporadic bursts of sewer gas and not a steady gas which indicates to me there is a build up of gas in the sewer lines. I'll try the peppermint test. Thanks.

I had two people spend the night to confirm the sewer gas odor. They said it smelled like rotten eggs. I also have natural gas. The gas company was here last week to check for leaks. They found nothing. Good idea to hire a company to perform odor tests. This way I'll know if I have more than sewer gas issues. Thanks.

I would look at the vents. At night, denser air brings the humid air down(inversion). A separated vent line could cause the issue you have. Unfortunately it could be inside a wall or other inaccessible place.