Problem with smell

Hello folks. I've noticed for a while that there is a smell, maybe sewer gas like, in my bathroom of my mobile home at the far end of the house. It is only occasionally, and I think I finally have isolated it to when I wash my clothes. I think that is. I'm on a private lot of 5 acres with a septic system -- only 5 years old. Is this perhaps a problem with my septic system (I doubt it because it's only 5 years old and the area where my lines are seem to be pretty dry right now. Plus, the smell is at the far end of the house only. Perhaps is it a vent line? How might I find the line if so?

I have 3 large dogs, so dog hair is a part of my washing machine situation. I only do about 3 loads a week, approximately. I don't think the smell appears when I take a shower, but I will try to check that out tonight. I rarely use the tub or shower in the bathroom where the smell occurs.

At first I thought it was my clothes dryer, which is located somewhat next to my AC/heating unit (almost seemed like the smell came from the vent) then figured it was really the laundry that was just washed. Again, the smell is only on the one side of the house.

Any direction anyone can give me would be appreciated. Money of course is a bit tight right now, and I'd rather not call out a plumber if I don't have to.

The vent line will be a pipe going out through the top of the roof. There may be more than one of them, especially if the bathroom is not next to the kitchen. Typically, it can be anywhere from 1.5" to 3" or so in diameter. It will probably stick up at least a foot - it depends somewhat if the roof has a pitch, or is essentially flat.

Thank you for the info! My roof is essentially flat and there are a few things sticking up. If it was a clogged vent pipe, where might I find where the catch would be (if there is one?). Would it be in the wall? What would it look like? Any advice what to look for?

Perhaps maybe I just need to run the washer more?

Well, if it were clogged, there might not be any smell ! Problem with a trailer is that the vent pipes aren't that tall, and therefore are close to possible window openings. If the wind is right, it can get smelly. If the smell is coming through an existing drain, then you might have a problem with a trap being dryed out, letting the smell out of the pipe. Have you isolated it to a particular place - a sink, toilet, or tub? Is there a window open when you notice it?

Well, there's a window over there, but I never leave it open. I can't figure out which drain it is, but there is a tub I rarely use, a shower I never use, and two sinks of which I only use one. It is a bathroom off my bedroom at the far end of the house. I use the shower at the other end. The washing machine is mid way through the house.

Can it be a dry drain? Should I plug up the drains? ( I usually leave them open).

It could easily be a dry drain if you don't use the fixtures. Just run some water down once in awhile. Since these will usually have an overflow, just putting a stopper in the drain would not seal off the gas from coming in. All you need is a cup or so, depending on how dry it is (being in a desert would make a difference!), maybe once a month. Try that and see if it stops.

Thank you so much -- I sure hope that is all it is!