My house has had this problem for a few years. When ever I run a large amount of water such as for a load of laundry or a shower I can smell a sewer smell coming from the crawl space which is where all of our pipes are. We have looked at all the pipes and none are leaking down there. We have a septic tank outside and well water. I need some advice.I have looked at drains in the laundry room as well. They seem fine. I poored water down them and do not smell anything from them. So it can't be a drain I don't use. All of the pipes have traps on them as well. I'm really stumped on this one and am about to call a plumber but I don't want to spend all that money if any one has any advice it would be much appreciated! Thanks!

You could have a pipe crack that is on the top and wouldn't leak or possibly a vent pipe separation. You need to look at all the piping close up and possibly be in the crawl space when a load of laundry is done. Do you have an ejector pump?

No ejector pump. I ran water down the tub and someone was down there looking at all the piping but found no leaks.

Going to have to inspect every inch of every pipe in the crawlspace. Look for any signs of leakage or cracks, or loose joints. It can be time consuming, and a real pain in a crawl space, but this is what you would be paying a plumber to do, so if you want to save some cash, your going to have to get in there and start investigating. Please let us know what you find.

Are you possitive the smell is coming from the crawl space?

Well. When we were down there looking around it wasn't really smelling so I went and ran a bunch of "cold" water down the bath tub and about 5 minutes after the furnace turned on. Then when the furnace was done it started to really smell under there. Im not completely sure that it was from under there but that seems to be where the smell starts.

Could it have anything to do with the air admittance valve on the washer and the softner?

Yes, possibly, AAV's can leak but with all the ones I have in my 2 houses or have seen, I've never had to replace one. Is your heater in the crawl space? Unless the heater is somehow drafting from the crawl, not sure about that unless your crawl is very tightly sealed. Not much of a way to get negative pressure there. Condensate pump connected in the crawl? You could have a negative pressure from the air handler and it is pulling from a cracked or disconnected vent line. As I and MGD77 said, you need to look further at the crawl piping.

No heater is not in crawl space but there is a huge vent that goes through there. I am not sure what a condensate pump is can you explain?

I thought I should add this. Whenever our softner regenerates in the middle of the night the smell is so bad that I wake up. Im wondering more and more if it has something to do with the softner?

Condensate pump, if so equipped, it a pump designed to remove the condensed water from AC and heaters and pump the water outside, or in some instances, into the sanitary sewer. If you don't have a heater in the crawl, you wouldn't have a pump their either. Just stretching my mind here.

I am not sure if this will help at all but I had a smell when after running water in the kitchen area of my mobile home. The thing is that water drains a long way to the opposite end of the home. So I still have no idea what causes the smell but if I put about 2-3 cups of Arm and Hammer washing soda down the drain with hot water the smell goes away for at least a few weeks.

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Originally Posted by grencha

I am not sure if this will help at all but I had a smell when after running water in the kitchen area of my mobile home. The thing is that water drains a long way to the opposite end of the home. So I still have no idea what causes the smell but if I put about 2-3 cups of Arm and Hammer washing soda down the drain with hot water the smell goes away for at least a few weeks.

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Note that this post was over a year old.

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Originally Posted by ma0641

Note that this post was over a year old.

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