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Bad smells coming from the drain. What causes sewer gases to come out of the sink?

Bad smells coming from the drain. What causes sewer gases to come out of the sink?

So your in-laws are visiting for the weekend, and when they arrive, you generously tell them that the guest bathroom downstairs is all theirs. The weekend goes smoothly, and you’re pretty sure they were impressed by your home . . . only to realize on Monday that the smell of rotten eggs is radiating from the fixtures in the guest bathroom.

It then becomes clear why they both opted out of taking a shower Sunday morning . . .

Sewer gas leakage is a common problem in many homes, and if you’re not aware of the causes of sewer gas, your in-laws may never visit again.

Sewer gas is a complex mixture of both toxic and non-toxic gases. It contains methane, carbon dioxide, sulfur dioxide, and nitrous oxides, as well as sometimes chlorine bleaches, industrial solvents, and gasoline from sewage treatment systems.

Below we discuss the causes of sewer gas, what to do when it’s leaking into your home, and how you can prevent it.

Causes Of Sewer Gas Leakage

Two features have been designed into your plumbing system to prevent the leakage of sewer gas—the p-trap and the vent.

The p-trap holds water in the shape of a “U”. This “U” creates a seal and keeps out the foul-smelling gases. If a drain isn’t used very often, like when homeowners use their guest bathroom’s tub as a bin for laundry instead of bathing, the water can evaporate and let the gas escape. We don’t often think about the fixtures we’re not using, which is why this is the most common cause of sewer gas leakage.

Aiding the p-trap in blocking this gas is a vent that covers the end of the pipe. This vent allows air in to equalize pressure, which forces the sewer gas to go up the stack and outside instead of up the drain. If the vent doesn’t equalize the pressure (because it is blocked or broken), odors will permeate through.

Simple clogs can also cause your drains to reek with sewer gas. The blockage can create a perfect environment for odor-causing bacteria to grow, and substances like hair will pick up those odors if it sits in there for any extended amount of time.

Remedies And Prevention

If the issue is a clog, than your first task is to remove whatever is in the pipe. Get a clothes hanger and fish out the blockage. In extreme cases, you might even need to get your pipes cleaned professionally.

After de-clogging, pouring vinegar down the drain neutralizes the smell in the pipes. If the sewer smell is still present in the room, put a few pieces of charcoal into a bowl and leave it in the area. The charcoal will absorb those nasty odors.

Odor neutralizing sprays also work well in this situation. Just make sure they’re odor neutralizing. Traditional sprays only cover up the smell; they don’t get rid of it.

To prevent sewer gases from leaking in the first place, it’s as simple as flushing your sink pipes regularly to keep the p-trap from drying out. If you’re going on an extended vacation, ask your neighbors to stop by and do it once or twice while you’re gone.

You also have to be conscious of the opening of your vent stake. Leaves and other debris can easily block the stack and create a problem.

If you suspect that for some reason your stack is leaking in a different area, you’ll have to call a professional to assess the situation and make the repair. That’s not one you can do on your own.

A Word Of Caution

Small amounts of sewer gases are just nuisances, and they aren’t terribly difficult to deal with, but larger amounts of gas can be dangerous. If high concentrations of sewer gas accumulate in an enclosed space, evacuate the area and contact your local fire department for assistance.

Final Thoughts

No one likes having to repair pipes or fish out blockages from the drain. The best way to deal with sewer gas, like many other plumbing issues, is to take steps to prevent it from leaking into your home in the first place.

Local plumbers are always available to answer questions and troubleshoot problems.

Have you ever had to deal with sewer gas?

What did you do about it?

Image: Flickr