Sewer Smell When Using Fireplace

Sewer Smell When Using Fireplace

Tom Grote, who lives in Ivoryton, CT, has an unpleasant experience when he starts a fire in his fireplace. It's not a smoking issue, it's a sewer smell. Read what he sent me:

"I live in a two-story colonial with a bathroom and fireplace on the first floor.

Every time I have a fire in the fireplace, I smell a methane/sewer-like odor coming from my downstairs toilet.

This ONLY happens when I have a fire in the fireplace. I do not smell anything when I am not having a fire.

I have read your posts regarding dried up fixture traps and debris in drain vent pipes at the roof, but I only have this problem when I have a fire going.  I've had chimney experts and plumbers out to diagnose the issue but no one can figure it out.

Any insight into the problem would be helpful.  Thank you!"

Well Tom, I'm wondering why the plumbers you brought in didn't simply install a new wax gasket on that toilet. That's a partial fix to the issue, but you really need something else to solve the problem. I explain it all below.

Here's the issue, and I've written about it on my website before.

When you have a fire going, just look at the volume of air / gas / smoke that's billowing from the top of the chimney. It's probably hundreds, if not thousands, of cubic feet of air per MINUTE when the fire is really raging.

For every foot of air going up the chimney, you need to replace it in REAL TIME with an equal amount of air.

If your home is well sealed, the fireplace starts to get the air anyplace it can as nature abhors a vacuum. In your case, the air is coming back in from your plumbing system.

This is a very dangerous situation because you could be also introducing carbon monoxide into your home at the same time. If you have a fire going while your gas furnace or gas water heater (I assume you have this - if not you, others might) is operating, the suction from the fireplace can cause NEGATIVE drafting down the appliance chimneys and exhaust gas comes backwards into your home.

You should install a fresh-air intake vent hood system at the very least to try to solve this problem. In the SHORT term, I'd simply crack open a window in the room where the fireplace is to see if this solves the sewer gas problem. It should solve it instantly. If you do still have the sewer gas problem, then open the window in the fireplace room wider as a TEST.

You want the makeup air supplying the fireplace to be as close to the fireplace as possible. 

Watch this video to see how Tim SOLVED a problem in minutes!