Sewer odor in residence

[DDYAZ]

Has anyone got an idea on what could be causing a "scheduled" sewer smell in my master bathroom? The smell only occurs in the summer and almost always occurs between 8:30 and 9:30 PM. The house is a single story built on a concrete slab in AZ. The master bath has 2 vanity sinks, tub, separate shower, and stool. I have made sure the traps are all wet, but the smell still persists. I cannot determine where the smell is coming from but I suspect the shower or tub. Is it possible the city does something at that time of night which causes some kind of pressure to force gas back through my traps? I have wondered whether I may have a vent problem but that still doesn't answer the timing issue. Also, the smell is not present in any other area of the house, and does not have anything to do with our showering/bathing schedules, etc. Thanks for any clues. This thing is driving me nuts and my wife into the guest bedroom.

 

[Caduceus]

Do you have a water softener the goes through a regen. cycle during that time? Is it possible there is any type of drain connected for a condensate line near the master bath? Sometimes mildew and scum build up in the sink bowl's overflow and using the sink or change of ventilation will draw the odor out of the drain. By pouring a mild bleach mix into the overflows you could remove some of the scum and odor. Just throwing a few ideas out there and hoping one hits. Pay particular attention to routine. If there is any activity that precedes the odor, make note of it and process of elimination could lead you to the cause (i.e. running the dishwasher, laundry, showering).

 

[Hyper48fan]

You may have a vent too close to the AC intake.

 

[DDYAZ]

Thanks for the suggestions. Unfortunately, the AC, laundery, and water softener are all on the other side of the house. But I am going to tape up the overflows on the vanity sinks to eliminate that source. Yesterday I duct-taped the drains and overflow on the shower and tub. Last night we had the odor again so I got up on a ladder to sniff around the AC and exhaust vents. Sure enough, I could detect a stronger oder by the ceiling exhaust fan. So I'm thinking I've probably got a bird's nest and rotten eggs in my exhaust vent pipe. Today I removed the exhaust fan and ran a snake up through the flex tubing about 4 feet, hoping to find some evidence of a nest before I venture up on the roof. I found nothing and no debris in the tubing. So now I go up on the roof and as I am just getting my head near the eave I can smell the odor. So I think the nest must be at the top of the exhaust vent about 6 feet further up the roof. Once I get up there I find the vent is clean and no sign of nesting material. I ran the snake down the flex tubing and again came up clean. The plumbing vent is a few feet from this location so I go over there and take a whiff. There is a smell, as I guess I would expect, but it was a weaker and different odor than what we were smelling in the house and what I detected at the roof edge. My idea at this point is I must have a dead something in my attic. I still don't know why we are not smelling this odor except at a certain time of night. Tomorrow morning I will go exploring in the attic. Hope to find whatever it is. Thanks again, DDYAZ.

 

[Hyper48fan]

Could be mold/mildew build up in the fart fan ducting, or the ducting could be disconnected and the moisture from the bathroom has been venting into the attic causing mold/mildew.

 

[DDYAZ]

Well my search of the attic found nothing that could be causing the odor. When I disassembled my ceiling exhaust fan the previous day I noticed the "el-cheapo" plastic flapper, which is supposed to close when the fan is off, did not appear to be closing properly. Now I am wondering if when the AC is running (there is a powerful blower on this unit) could there possibly be a negative pressure created in the bathroom, allowing fumes from the plumbing vent on the roof to sneak back into the house past this questionable flapper in the exhaust fan housing. I mentioned in a previous post that the plumbing vent is a few feet further up the roof from the exhaust vent. If anyone has encountered such a situation I'd like to know about it. In the meantime I've temporarily sealed off this particular exhaust and will see if it makes any difference in our nightly smell test.

 

[Hyper48fan]

Tooth brush holders can stink pretty bad after a while too.