I am wondering if anyone's had a similar problem. I am not sure what to have checked. We live in a manufactured home, where the plumbing was done by a master plumber, and we have an aerobic septic system - which we have checked every three months for maintenance. No issues that we know of. We have lived here for a number of years, and just within the past few months we have started having an intermittent problem with a horrible sewer-ish smell, or rotten egg smell. I use our clothes washer and dishwasher DAILY. I have noticed after several hours of not using the water (not all the time though) such as when we first get up in the morning, things will be fine but then I can run the water from our kitchen sink, and the smell comes from our laundry room, which is adjacent to our kitchen. Do I need a plumber, or could it be a problem with our septic system? Or is it a p-trap problem or a venting problem? I've even wondered if there is something clogging the pipes between that area, but the water always seems to drain fine. My husband checked the roof for venting, and there is no vent coming from our laundry room area. The closest vent is about 20 feet away near one of our bathrooms. I am just not sure who to call. Anyone have suggestions or advice? Anything would be appreciated!

Suggestion.
Next time you smell the odor, slowly pour about a pint of water down the laundry drain. Let us know if the odor goes away (for a while).

Hi Harold,

I actually have done that, and it does indeed go away for a bit. I think I poured WAY more than a pint of water though. Thanks for your reply.

Harold and I are probably both thinking the same thing, your trap is being siphoned by a clogged vent. Al drain systems are trapped abd vented, you must allow air in the drain pipe to escape to avoid siphoning the traps.

This is probably a blocked or restricted vent but the inference I get here is that this only happens when no water has been used in the house for a period. That makes me want to think that the laundry has a leaking trap. Since the laundry is next to the kitchen, the laundry drain may be wet vented to the sink and the trap being replinished durnig normal use. (I can't really explain how). After a period of no use and a slow leak in the laundry trap, the trap is dry.

Is the laundry just a washer stand pipe or do you have a laundry sink?
Can you see the trap?