Smelly Shower Drain? Here’s How to Fix It

Why Does My Shower/Bathtub Drain Smell so Bad?

Is there a pungent sewer/rotten eggs smell coming from your shower drain? Does it come immediately after draining the bathtub, flushing the toilet or it is constantly there?

You should never ignore a sewer gas smell in your bathroom. In most cases it is the telltale sign of a bigger underlying problem. In some instances it is actually not that serious. Whatever the case it is always a good idea to fix it as soon as possible.

A smelly shower drain is mostly caused by a dry P-trap, accumulation of biofilm/bacteria/mold in the trap or drainpipe, a blocked vent stack or a clogged drainpipe. It could also be as a result of a full septic tank.

Unclogging the drainpipe or vent stack, cleaning the P-trap or emptying a full septic tank will help get rid of the smell from your shower drain. If unfortunately you are dealing with a leaking trap/pipe you will need to call in a licensed plumber to help you fix it.

Let us first go through the different scenarios you might experience to help you solve the problem easily.

Shower drain smells like rotten eggs – A rotten eggs smell is basically hydrogen sulfide gas. This means that either sewer gases are backing up through your shower drain or biofilm has built up in the P-trap and drainpipe.

Bathroom smells like sewer after shower – This means either the drainpipe or vent stuck is clogged. When the shower/bathtub drains, sewer gases trapped in the drainpipe are forced out through the shower drain.  It could also be also be as a result of a leaky or dirty P-trap.

New shower drain smells – If you have a new shower drain that is smelling while other house drains aren’t, you most likely have a problem with the P-trap. Either it was not properly installed or it is not holding enough water to seal off the sewer gases.

Shower drain smells like urine – Whenever you smell urine from the shower drain, there is a very high likelihood that someone in the family peed in the shower or there is mice in your house, which tend to have such a strong urine smell.

How to Fix a Smelly Shower Drain

Getting rid of that awful smell from your shower drain can be a very easy job or a difficult and expensive one. We will start with the easiest thing you can do and hopefully it will be enough to fix your problem.

Here are the different methods to get rid of smell in your bathtub/shower drain:

1. Fix a Dry P-Trap?

A P-trap or a drain trap is it is commonly called is a piece of pipe that is found in every drain in your house. It looks like a U or an inverted P. You cannot see it in your shower drain but if you check under your kitchen or bathroom sink you will see it.

Look at the image below of a kitchen sink drain trap. Your shower has the same trap just that you cannot see it.

So why do drains need a P-trap?

  • When something that is not supposed to be flushed down the drain end up being flushed, it is held in the trap making unclogging drains easy. Otherwise the item would unclog the drainpipe further away where it would be harder to unclog.
  • It always hold a certain amount of water. This water creates a barrier/seal which prevents sewer gases from coming up in your bathroom.

If you have not used your shower/bathtub for some time, the water in the trap will evaporate breaking the seal. Sewer gases will then starting flowing out and hence a smelly shower drain.

If that is the case, open your bathtub/shower faucet and let water run for a few seconds. This will replace the evaporated water in the trap. Check if the sewer smell has gone.

If you regularly use you shower, your P-trap could be dry as a result of a clogged vent stack. To be sure if that is the case, open the bathtub water faucet or shower head for a few seconds then flush the toilet.

Do you hear a gurgling sound from the shower/bathtub after flushing the toilet? If so, the vent is clogged. When you flush the toilet, a vacuum is created which sucks water from the shower’s trap and hence the gurgling sound.

If none of the above is the case, you have a leaking P-trap or drainpipe. It could also be that the P-trap was not well fitted especially if you have a new shower drain.

A leaking P-trap/drainpipe is however not something you can fix on your own. You will need to bring in a licensed plumber to help you fix it.

2. Clean the Shower Drain Trap

Sometimes your shower drain could be smelling because of the gunk/grime trapped in the P-trap and drainpipe. The products we use in the shower are mostly organic. Soap, shampoo, conditioner, shaving cream etc. are usually washed down with the shower waste water but some accumulate inside the trap and drainpipe. This accumulation is called a biofilm.

Bacteria (which are everywhere) will then start to act on the biofilm and that is where the sewer gas smell from the shower drain starts getting noticed.

So how do you know that you have biofilm inside your shower drain? Apart from the awful smell, you will notice that your shower/bathtub is draining slowly. This is because the biofilm creates a restriction inside the trap and drainpipe.

Here is how to clean a shower drain trap:

  • Remove your shower drain plug. If you have a pop-up drain stopper, turn it counterclockwise to loosen and remove it.
  • Pour about 1 gallon of hot water down the shower drain. This will dissolve soap scum, mineral deposits as well as wash away any loosely held debris in the drainpipe and trap.
  • Next pour half a cup of baking soda down the drain.
  • Slowly pout 1 cup of vinegar. You need to pour the vinegar slowly since it reacts very quickly with the baking soda.
  • Leave the solution for 30 minutes to work out its magic.
  • While the baking soda and vinegar reaction is breaking away the biofilm, grab a drain brush and insert it in the shower drain. Shove it up and down as well in a circular motion. A paint roller is also a great option. It fits perfectly in your shower drain opening. Moisten it with your usual cleaning solution and push it in and out of the shower drain. If you don’t have a drain brush or a paint roller, an old toothbrush works just as well.
  • After the 30 minutes, blast hot water down the shower drain to rinse and wash away all the broken down debris.
  • Put back the shower drain plug.

These solution works out very well and you should do it often even if your shower drain is not smelly. If you have a tiled shower floor, biofilm can also thrive on it. Use the vinegar and baking soda solution and brush to properly clean the floor at least once every week.

3. Unclog the Vent Stack

So, do you know how a clogged vent stack affects your shower drain? Each of the fixture in your house has its own independent drainpipe. All these drainpipes eventually empty their waste into the main house drainpipe.

The main house drainpipe then empties into the city’s sewer lines r septic tank for those on a septic system. In essence, your house plumbing resembles a river and its tributaries. Another pipe runs from the main house drainpipe through the roof of the house. This is called the vent stack.

The vent allows air to flow freely in and out of the drainpipes. Sewer gases are hence able to flow outside and not back through the drains because of the vent.

If the vent is clogged, sewer gases have no way of flowing out of the drainpipe. There is also no free circulation of air. As a result, a vacuum is created inside the drainpipe which sucks the water in the P-trap.

Dry leaves, debris, dead birds and rodents are some of the things responsible for a clogged house vent. It could also be caused by snow especially during winter.

Here is how to unclog a vent stack:

  • Climb to the roof of your house armed with a garden hose.
  • Locate the vent, usually above the bathroom.
  • See if there is any blockage you can remove with your hand.
  • Insert the hose inside the vent and have someone turn on the water. Hopefully, the weight of the water will overwhelm the clog forcing it to wash down the drain.
  • If the vent instead fills with water, it means the clog is quite intact. Upgrade to a better to tool.
  • Get hold of a plumber’s snake and feed the cable down the pipe until you encounter resistance. Crank the handle clockwise and counterclockwise until you go through it.
  • Pull out the snake

And basically that is how you unclog a vent stack.

4. Unclog the Drainpipe

If the main house drainpipe is clogged, it means waste is not flowing out to the city’s sewer lines but is instead stacking up in the drainpipe. When you drain the bathtub or flush the toilet, the waste compresses air in the drainpipe which is forced out of the shower drains in form of bubbles.

No amount of plunging will unclog a clogged main house drainpipe. You will need to get a plumber snake.

Here is how to do it:

  • Remove the shower/bathtub drain stopper.
  • Feed the cabled down the drainpipe until you encounter resistance.
  • Start cranking the head back and forth till you push the auger head through it.
  • Pull out the cable slowly.

If you are not very comfortable using a plumber’s snake it is best if you call in a plumber to help you take care of that. Wrong use of the auger can damage the drainpipe.

5. Empty Your Septic Tank

A full septic tank has the same effect as a clogged drainpipe. Waste from the house drain start accumulating inside the drainpipe. If you don’t fix it fast enough you will not only deal with a sewer gas smell but raw sewage will back up from your house drains which is not very pleasant.

Emptying a septic tank is however not something you can do on your own. Apart from a sewer gas smell, one of the other signs that your septic tank is full is very green lawns or water pooling in the lawns.

Finally

Although I have given you a detailed account of what could trigger a sewer gas smell to come from your shower drain, most of the time it is usually the biofilm/mold or issues with the P-trap. If either the vent stack or drainpipe are clogged, the other drains would also be affected and not just the shower drain. The same thing with full septic tank. You would therefore have a sewer gas smell in the house/bathroom.

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