What causes sewer smell when the furnace kicks on? It does not happen any other time, could it be something with the vent pipe?

Where is the smell the strongest? Back to you, Tom

It comes through the floor vents.

Hi Jgulizia...

Do you have a CONDENSATE PUMP (see image)? Do you have a drip pan associated with your furnace? If you do, it could be that the condensate pump needs to be cleaned/cleared or replaced.

Here, if the pump isn't working properly then condensate could be collecting in the drip pan or even getting stuck in the furnace causing sewer like smells through the vents much like you describe.

To test this, you could pour some water into the condensate pump (through little hole on top) and see if it turns on and discharges as it should... follow the clear hose to the discharge point (usually a sink or standpipe by a washing machine). If no discharge then the pump is gone and needs to be replaced.

The few times I heard this complaint, the condensate pump was the issue. It can be easily replaced (just disconnect the drain hose and unplug) and is available at all home improvement centers.

I am sure Tom will be along shortly to share his thoughts as well!

Back to you...

Mark

If it turnsn out to be the pump try adding a little bleach the small hole on top to chase any bad smells away,
Tell us more about your home. I'm assuming you have a basement. What type of furnace do you have? Is the AC and furnace combined? Where's the cold air intake located? Is it near a floor drain or basement bath? Does the smell go away after the furnace runs for a while? Let's have more details. Regards, Tom

The furnace is located in a crawl space, not certain where the cold air intake is located, yes the smell does go away after the furnace runs for a few minutes.

Wouldn't hurt to check and change the furnace filter and see if that helps.

Always through the vents doesn't happen every time but immediately when the furnace kicks on and for a few minutes after it runs.

Listen, there was no need to give me a negative comment for suggesting you check your filter. I had no way of knowing if you change it once a month or not. Im sorry if I couldn't be of help to you, but a reddie is definitely uncalled for. This is the sort of thing that keeps me away from the desk for long periods.

Furnace filters are changed regularly every 30-45 days.

Sorry was not meant to be negative in any way..

I believe I simply provided answer to your question and never intended for it to come across negatively... my apologies.

No problem, it is set up a little confusing the way they word it helpful or not helpful. It shows up on my page as a reddie(negative comment) vs a greenie, (possitive comment). If anyone were to go to my profile and look at my received comments, every reddie makes me look not so good. I understand its near impossible for a new person on the sight to know how these things work, heck, I'm still trying to figure it out. So anyway, no hard feelings, and I hope the other pros here help you get rid of the smell. Take care.

Thank you so much for your help..

MGD I see no reddie but do see 3 greenies. I am left wondering how one person can rate the same person 3x, thought that was not allowed. Maybe it's the new skin thing that allows it

Hi ballengerb1,
Yep, I'm confused too. I believe jgulizia first hit not helpful, and then somehow went back and changed it to helpful and added a couple more greenies for good measure (thanks for that jgulizia). Not sure how the new setup works, Im kind of fond of the old system, but that's just me. Wish I new how to change those reds to greens :)