Shower drain smell

On 8/26/6, after nearly 20 years, we started to get a smell coming from our shower drain. This is a shower that has been used twice a day for the last probably three years. Before that it was used once a day for a couple of years and before that periodically since it was built as an add on as a part of a master suite to our 28 year old home.

Ran liquid Drano, flushed it with the garden hose, cleaned it above the trap with Clorox and a bottle brush. (There is water in the trap and it stays at a constant level when the toilet is flushed, an adjoining bath tub is turned on and water is run in two sinks hooked to the same drain pipes). Called the plumber. He said it was caused by the heavy humidity and will go away. It went away and came back a couple of times. Besides, that answer just didn't sound right. Called the city. A man came out and said it did not smell like sewer gas. He pulled the cap off of the clean out and no odor there.

Ran a snake down the vent pipe, no obstructions. Put a white rubber sink stopper over the drain and put a pitcher of water on it. Kept the smell out of the house and turned the white rubber brown.

Called our contractor and he suggested pouring Clorox in the trap and let it set over night. Didn't work. Poured Liquid Plumber, ¾ bottle, in the trap and left it over night. Didn't work. He also suggested running a snake down and see if it picks up anything. Ran the snake in about eight feet turning it contatntly. Came up with nothing. Just talked to him and he suggested asking the question on this forum.

Thank you out there for the help.

God Bless
Dick

Out of that bath group that trap is the lowest amoung the sinks and toilet.

Run the laundry or dishwasher in the house and see if that water in the trap becomes disrupted.

Those two fixtures alone dump the largest volume of water at one time and possibly, possibly that is causing the trap to emit sewer gases from time to time.

There is validity to the humidity scenario. Wet weather, closing up the home for the first time since summer.

The gas utility in my area loves me; I pick up on all those gas leaks at this time of the year since the windows are closed and sure enough, time to replace piping to fix the leaks. Keeps both the gas company and I employed and the customers very thankful for finding the leaks.

In some parts of the country, and with hacks everywhere, they don't understand that the shower pan should go on top of the preslope, and not directly flat on the floor under the shower. Tile and grout are not waterproof - a little moisture will get under the tile and, if the waterproof liner is not sloped, can accumulate if the shower is used on a regular basis. When used occassionally, it usually has a chance to dry out...when used more often, it may not. So, while this method of construction may not leak, if you have it, could easily be the source of it smelling.

www.johnbridge.com is a good resource on tiling thing as well.

Are you on a slab?

Quit pouring chemicals.

RUGGED said:

Out of that bath group that trap is the lowest amoung the sinks and toilet.

Run the laundry or dishwasher in the house and see if that water in the trap becomes disrupted.

Those two fixtures alone dump the largest volume of water at one time and possibly, possibly that is causing the trap to emit sewer gases from time to time.

There is validity to the humidity scenario. Wet weather, closing up the home for the first time since summer.

The gas utility in my area loves me; I pick up on all those gas leaks at this time of the year since the windows are closed and sure enough, time to replace piping to fix the leaks. Keeps both the gas company and I employed and the customers very thankful for finding the leaks.

Click to expand...

The section of the house where this shower is, is a new addition and on a seperate sewer system than the dish and clothes washer. It conects to the older house system just before it goes to the main sewer. Does that information change your recommendation?

We are in Texas and the home remains closed year round pretty much. Those two days each year when we have spring and fall, we may open the windows. Have not had this problem in 18 years.

Are you saying that the smell may be natural gas?

Cass said:

Are you on a slab?

Click to expand...

Yes we are on a slab.

Dick D said:

The section of the house where this shower is, is a new addition and on a seperate sewer system than the dish and clothes washer. It conects to the older house system just before it goes to the main sewer. Does that information change your recommendation?

We are in Texas and the home remains closed year round pretty much. Those two days each year when we have spring and fall, we may open the windows. Have not had this problem in 18 years.

Are you saying that the smell may be natural gas?

Click to expand...

No and No.

I'm at a loss to know what it is without being there.


Are you sure that you've isolated the source of the smell.....and possibly not the overflow of the sink or the wax ring on the toilet?

Had the toilet been clogged/recently plunged?

Is this a tile shower floor or a fiberglass base?

try "rot under the shower base"

Well, you certainly have done your homework, Dick. Congratulations on that.

Nothing else changed in your habits regarding water use, am I right about that? If the P-trap is not getting sucked dry, no gasses will come back up through the drain.

What Jim said is a possibility, but I recommend you stay in this forum for a plumbing smell problem. A "smell from under the tiles" is a result of many years of water seeping onto a shower membrane laid flat. This often is found on showers built on slabs, since it is, or was, a normal approach for tile-layers to lay down the waterproof liner membrane immediately when presented with a beautiful flat slab and to build a sloped concrete tiling base on top of this flat liner. It's a possibility. The smell is a bit different from sewer gas, because of the growing conditions for mold under tile. A couple ideas I have about how you might eliminate or isolate this possibilty. One is a minute visual inspection of the grout lines. Use your nose too. The other is to flood the shower pan for many hours and see what you get. A plastic bag filled with water can block the drain sufficiently. You could also use the draining time to conduct a couple of "linkage" tests with other drains too, if you control the drain to let only a small flow of water out so it doesn't build up any momentum.

Your case is fascinating and I am sure the group following this thread will be able to help you. Reminds me of other cases where the homeowner has done all the work to diagnose the problem and still not come up with even a single valid clue. They always get good ideas, and eventually solve the puzzle, when they keep sharing their progress.

By the way, today's Plumbing Codes spell out explicitly that a waterproof liner (membrane) must be sloped, although that little half-sentence is often overlooked or not understood. The idea is to enable the small amount of water that does seep through grout or through minute grout cracks not to stagnate but rather to slide slowly toward the drain, through the porous cement under the tiles. The base for the shower liner is a pre-slope built with a mix of cement and lots of sand. If someone does not know about this today, or does not build showers this way, then either they are "ignorant of the law" or lazy and unprofessional. If a liner is flat, water stagnates and eventually produces a mixture of moisture and organic matter (skin cells, soap residue) that fosters a mold colony, which can grow like wildfire at a certain point.

David