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Have your furnace inspected and serviced by a professional heating contractor.
Question: We did major renovations on our home in 2006-08, one of which was a new furnace, ducting and central air. The furnace is located in an enclosed closet and outside the closet is our washer and dryer. Last year we replaced our dryer and connected it to the existing ducting. But we could smell the dryer exhaust and realized that the connection needed to be tightened up. But, since the winter was here, we welcomed the extra humidity. Then, we had an issue with our central air and needed to replace the unit. Before we did that we realized that the dryer vent had come off, as we had dryer fluff on the walls in the furnace room. We cleaned that up and installed a new metal dryer vent and tightened up the connection to the back of the dryer. There is an opening in the wall in the furnace room so we can access the back of the washer.
We got a new AC unit and we were glad to have it installed as the hot, humid weather was here. But this is now our problem: when the AC is running, we get a sewer smell in our only bathroom. We put a snake down the outside vent stack and also put the outside hose in it, to flush it out. We have a holding tank and we could see no problem with the vent, as the water was running freely into the tank. We thought we had cured whatever the problem was, but the smell is still there when the AC is running. We checked our plumbing below the bathroom, as we can access it through our crawl space. No moisture or leaks from any of the pipes were found. We have been leaving one or two windows open enough to stop the smell. But, with winter coming, that is not a great idea to do.
Do we need a plumber or a heating/AC person? I don’t see any furnace fresh air vent, as the furnace is electric. So, was the furnace using the dryer vent as a fresh air vent? We have another roof vent above the kitchen but haven’t had any smell in that area. There is a vent stack of some kind behind the washer. Would that be the fresh air vent for the furnace?
Thanks for reading.
— Leta Lee
Answer: Identifying which professional to hire to figure out what is causing an odour in your home may require correctly identifying the odour itself, first. Then, hiring the correct service technician or tradesperson should solve the problem.
Often, homeowners will identify an issue in their home and misinterpret what is happening or the root cause. While you say you have a sewer smell, it is only noted when you are running your air conditioner. That is not unusual, as the AC unit will circulate air through the house ducting when operating, spreading any odours throughout the home. While this may indeed be a problem with the plumbing waste system, it may also have alternative sources if nothing is noted the rest of the time.
Since the furnace is electric there is no need for fresh air for combustion, but the damaged dryer vent may have let some fresh air into the home. I doubt that would have been enough to cause this issue when eliminated, but the fresh air may have helped mask the odour if the source was nearby. More likely, the moisture from the damaged dryer vent caused mould to grow, which could be mistaken for a sewer-like odour. Look in the area around the laundry for mould — including under the washer and dryer — and clean it or remove mouldy wall coverings if found.
Closing all the windows and not running the AC or heat on mild days may answer your questions. If you suspect that the odour is coming from the furnace/laundry area check it after several hours with the house closed and the furnace fan off. If there is no odour in there, check the rest of the home to see if you can find the source. Leaving your home for a short period and then re-entering and quickly closing the door may help you avoid desensitizing effects that can occur. If no odour source is found, it is less likely that the smell is related to the plumbing.
If the smell re-emerges when you switch the AC back on, you may have mistaken the source of the problem. There could be something that has fallen into and rotted inside your heating ducts. This could be something like a mouse or squirrel, or other organic matter like fruits or vegetables. Alternatively, there could be a problem with the refrigerant in the new AC unit, with a possible leak creating the foul odour. Finally, when the air is circulating through the house ducts it can cause air pressure differentials, but that should be nothing that has changed dramatically with the new upgrades. In that situation, calling an HVAC contractor to check the newly installed AC may yield an answer.
If you are sure it is a sewer smell, then there is probably a venting issue with the plumbing system. This could be an improperly installed trap under one of the plumbing fixtures or a lack of proper venting for one or more. The laundry area pipe you have noted is likely the drain for the washer, which should have the washer discharge hose inside. If not, and the laundry drain has been moved to another area, this drain pipe may be the problem. There should be a trap at the bottom of this pipe, which may have dried out if it is no longer in use. Try pouring some water into this pipe, to fill the trap, and see if it solves the problem. If not, calling a licensed plumber to identify the source of the stink will be the next step.
Calling either an experienced HVAC technician or a plumber will likely heed an answer to your smelly home issue, but deciding on which to enlist first will depend on the actual nature of the odour. If you are not certain that it is a sewer gas smell, getting an HVAC tech in to check the new AC unit for defects is prudent; otherwise, enlisting a licensed plumber to check for trap and venting issues is your best bet.
Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba (cahpi.mb.ca). Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at trainedeye.ca.
trainedeye@iname.com
