I have a septic smell problem. The smell appears after a heavy rainfall or when there is a drastic thaw in the winter. Any ideas? I have a septic system and well water. The smell seems to resonate throughout the kitchen and living room over which there is a crawl space.

Have you checked your vent stack, is it clear and open? It should be above your roof line. Even a failed wax ring on a toilet can cause a sewer smell so check the bathroom too

With a septic system there are a few questions first. How old is the septic system? How long have you lived in the home? Are you familiar with how the system works? When was the last time the tank was pumped? Have you had any recent clogs or back ups? Maybe by answering these questions it could give us or even yourself a better lead as to where to start.

The system is about 30 years old. I've lived in the house 4 1/2 years. The septic tank drains into the back yard through perferated septic lines I believe. Just 2 of us living here and there hasn't been any clogs or back ups that I know of.

The tank was pumped 2 years ago.

If you can, check to see if it is full again. Typically a septic will have only toilet water going to the tank and the other drains to a leech bed of sorts. But, depending on use and actual drainage connections, it may be time to pump it out again.
I was hoping that your response would also include if you checked the tank to see if it is full.

Pgh where do you work, what state or country. I have done extensive work on septic and have never seen one where all sewage and gray water did not all go to the tank first. YouTube - An Introductory Guide to Installing a Septic Tank and Drainfield (English)

I'm in Pennsylvania. In all regions of the country, when septic systems were being installed to replace outhouses, the standard installation was for soil water to the tank and "gray water" to leech into the soil. Waste water and soil water are different. Sometimes the waste water would bypass the tank and disperse into the leech bed/field after the tank. This reduces the burden on the tank and frequency of pumping the sewage from it. Now that plumbing systems, tanks and environmental situations are changing, you may find more differences than similarities in septic systems. Many codes still allow gray water dispersal but strict regulations regarding water table, encroachment to properties, high costs, etc. make it more practical to put everything into the tank or connect to a public sewer. Most people will assume all of their waste water goes to the tank but even floor drains will sometimes just lead to a gravel pit under the dirt.

K mclean, my post to ballengerb1 may also give some insight to your problem. If you have a gray water drain for your kitchen (where the water goes into the soil, not the tank) heavy rains may saturate the ground and the odors are getting into the house from the drain. Also check traps under sinks and floor drains to see if they have water in them to stop sewer gases.

"In all regions of the country, when septic systems were being installed to replace outhouses, the standard installation was for soil water to the tank and "gray water" to leech into the soil." Maybe I am being too picky but I can not accept this statement. I can not speakm for "All areas" but I work in 2 counties in Illinois and neither allow for any sewage water to go directly to the field. All the rest of your answers to k_M's issue are spot on. Can you give me a link to your codes or septic design prints for PA? http://www.webdesignpros.net/consult...pticsystem.htm

Okay, perhaps "all regions" was too general. Different areas will have different designs such as in the video. (Very sandy soil.) The codes and designs vary from county to county. I'm sure you could find the state's general septic codes and requirements as I could on the internet. Mind you that MOST modern designs will include all drainage to go to the septic and is required to do so... depending on the area. Most recent septics we've dealt with was all sewage to tanks (3) and open air dispersal to fertilize the fields and wooded areas of the property.