In a previous post we “solved” the mystery of the rotten egg smell in your home’s plumbing. Now we take a closer look at what to do about it.
Before digging in, it helps to have a basic understanding of how the plumbing in the home, specifically in the bathroom.
You’ve certainly looked under the bathroom sink and into the cabinet underneath. You probably noticed a U-shaped pipe that runs from the sink drain above to a larger wastewater pipe in the wall. Few people ever really pay attention to the U-shaped pipe, or the P-trap (images), except to note it gets in the way when storing cleaning supplies or hand towels.
One end of that big wastewater pipe runs down to your sewer or septic system; the other end actually leads all the way up through the roof (images), letting fresh air in while allowing any smelly sewer gases to vent out. And although you can’t see it, the same basic drain setup is at work behind or beneath your tub and shower.
The U-shaped section of pipe below your sink is called a P-trap. When everything is working as it should, a small amount of water stays in the P-trap after you turn off the sink, empty the tub or flush the toilet. That little bit of water is actually valuable — it prevents gases from drifting out of the sewage system and into your house. Under normal conditions, those gases flow right past your bathroom and out through the vent pipe in your roof.
Problems in the Bathroom
But if you have a sewage smell in your bathroom, it usually means something in that very basic system has gone wrong. If you’re lucky, it will be an easy fix. If not, it may require a call to your plumber or plumbing contractor for inspection and possible repair.
The first possible cause of a sewage smell in your bathroom is by far the easiest to fix.
If your bathroom fixtures haven’t been used recently (the sink in a guest bathroom or the tub in a bathroom with a separate shower), it could be that the water in the P-trap has simply evaporated, removing the barrier between your bathroom and the gases in the sewer system. If that’s the case, run some water to allow the P-trap to fill up again.
(Note: If you smell the odor in a bathroom that’s being remodeled, be sure to cap any open drain pipes until your new fixtures are installed.)
Check for Leaks
If there’s still a sewage odor after you’ve run plenty of water down all the drains, or if you notice a sewage smell in a bathroom that gets regular use, check for leaks in or around the P-trap.
Believe it or not, if even a small amount of water has leaked out of the bottom of the “U,” sewage gases may be able to sneak in. The leak may be so small you will not see it with the naked eye.
One thing to try is running water into the sink. Clear the area around the P-trap so you have access to the pipe. Turn on a portable light under the sink so you can see the pipe to inspect. Look for droplets of water forming on the pipe. Be sure to check behind the trap. If this does not work, you can always take a dry paper towel and wipe down the pipe. If there is moisture on the outside, the paper towel should pick it up and alert you to a tiny leak.
Another possible cause that’s kind of gross but fairly easy to resolve is a clog in the drain, since the clog itself can become smelly. Popular culprits are hair and soap scum, sometimes mixing with makeup and cosmetics.
This is fairly easy for homeowners to fix and shouldn’t require the assistance of a plumber. Again, clear the area around the P-trap, especially underneath because water or scum might bubble out of the pipe.
Have an old pair of tweezers, needle nose pliers, even the end of a hanger, to fish out the hair, soap scum, pieces of soap, safety pins, or anything else that might have lodged itself in the drain (images).
When unscrewing the plastic collar or nut that connects the pipes, be careful not to force it. This probably has not been unscrewed in years and may be difficult to open. Take a pair of channel lock pliers and carefully fit it around the collar and carefully unscrew it.
When screwing the collar back on and re-connecting the pipes, don’t over tighten. Make sure the pipes are not torqued or twisted in any way. You want them to align properly. Run some water to make sure no new leak has developed. When it comes to plumbing and water, a homeowner cannot be too careful.
If the suggestions above don’t lead you to the source of the sewage smell, you may be dealing with a more complicated issue and should call a plumber for assistance.
Call a Plumber for Repair
There’s water in all the traps, you have no visible leaks, and the pipes are free of clogs. What next?
It seems natural to assume that the toilet would be the obvious source of any sewage smells, but if there’s water in the bowl, chances are the commode is not the problem. (The water here acts as a smell barrier — just like the water in a sink’s P-trap.) But if the bowl doesn’t fill up as it should, the problem could be a broken seal, in which case it may be time to call your plumber.
Replacing a toilet bowl seal is something most homeowners can do, but some people may not want to deal with it. For one, you’ll need to lift the heavy toilet bowl away from the waste hole in the floor. For another, it’s kind of a messy job. That wax seal has probably deteriorated, and you’ll need to scoop away the remaining wax to prep the surface for a new seal. You’ll also need to lift the bowl and align it properly on the new seal, then place the tank on the bowl and tighten.
Which seal to use? There are many options at area home improvement centers, but our answer is to keep it simple. The wax seals work fine. We don’t recommend buying the cheapest seals, but we don’t recommend buying the most expensive either. If you have any questions, ask the sales rep for a good middle-of-the-road, quality wax seal.
Things get even trickier when the smell is coming from inside the bathroom but the problem itself is somewhere else. A roof vent blocked by a bird’s nest, leaves, or snow and ice prevents fresh air from coming into the plumbing system and gives sewage gases nowhere to go but your bathroom drains.
A vent pipe that’s been improperly installed or cut can also send offensive gases into your home. (Believe it or not, contractors have been known to vent these pipes into attics and crawl spaces instead of out through the roof.) And a cracked vent pipe can be even harder to track down, since the break is probably hidden somewhere within your wall.
This is where a plumbing expert can really help. And while it will cost you some money, the plumber’s expertise is worth it considering because of the amount of time and frustration you’ll save trying to pinpoint the problem.
A repair plumber uses a device known as a smoke machine, which fills the drain system with a harmless but visible smoke. When the smoke finds its way out, you’ve found the source of the leak and can determine a repair strategy.