Why does my crawl space smell like a sewer?

Question

OK, just had a plumber in and he was stumped, so now I am getting worried.

Problem: I have a restaurant in a 100 year old building, all new plumbing (2 years). Recently (a week and a half ago) the bathrooms started to draw some bad smells up from the floor because of the exhaust fans. I went down to investigate in the crawl space and found that the smell was indeed concentrated around the bathroom (verses the prep sinks) but no leaking of any type and no apparent source of escaped vent gas. The smell is quite strong; stronger than taking a up close whiff of the open soil stack.

The toilets have been flushing fine except for one clog in the men's room last Thursday which has happened from time to time since we first opened and the pipes were brand new. Plunging for fixed the problem immediately as it always has. The smell remains.

Additionally, the city sewage treatment plant smells particularly bad right now, but I don't know how that would tie into my problem.

-Dave

Answer 1

i wonder if you have too many S curves or P traps in your system...you know, a piece of pipe that could let the smell just sit there?  Since you say you have had clogs 'off and on' since you opened, makes me wonder if the people who installed your piping did it correctly.  

Answer 2

I agree with having it scoped.  I had a similar problem in my crawl space with all new plumbing.  They came with a scope and discovered that a pipe was broken under the floor and that is where the odor was eminating from.  Moreover, rather than digging up the floor to replace the pipe, it is less mess and cost to have the new pipe inserts installed that encapsulate the break by coating the inside of the pipe and it is warranted for 15 years.

Answer 3

You might want to get a plumber who can scope it with a camera to see if there is a break in the line that could be causing the odor.

Answer 4

You may have a joint in your 3-4" sewer line that wasn't glued. I take it your drain lines are white pvc. Sometimes this happens as plumbers dry fit joints to make sure they are aligned, then take apart and glue. This joint could leak when stools are flushed and weight of water,sewage opens up joint.

You need to get under crawl right where the stools are, have someone flush stools and look for leaks, or put large pc. of cardboard under stools and see if over time there are wet spots on cardboard.

Also sometimes plumbers use what we call *pro-vents, they are in line vent caps that open to let air in so drains work, it's possible you have one of these and it is stuck open- which lets gas out and if you plunged stools it might have forced some debris up into pro-vent and caused it to stick open.