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Thread: Can mold grow inside a drain pipe in a shower?

  1. #1

    Default Can mold grow inside a drain pipe in a shower?

    Every six months I use a snake to get out the giant hairballs that accumulate from my wife's long hair and it smells nasty. But I just had the concrete sub-floor in my stand-in shower replaced because it was crumbling and smelled horrible.

    Now the new concrete has been poured in but I think the smell is coming back. This is a second floor shower so it's not near the sewer line, and there is water in the trap, and we just replaced the top of the shower drain.

    When I look down into the drain I see a brown film just above the water line in the trap and I scraped it with a Q-tip. Boy it smelled. Can I get this film off? Is this what's causing this smell?

    Thanks!

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Any organic crud above the trap can end up smelling. What are your pipes made of? Smooth plastic makes it harder for the crud to adhere. Soaps, oils, skin flakes, hair, anything that is above the trap can and will likely start to smell. The shorter the fall, and the higher the water level in the trap, the less surface area. You could use a bottle brush to clean things after removing the shower grate.

    Note, a common shortcut when building a shower is to install the liner flat on the floor. This in itself can lead to mold buildup in a shower. The tile is not the waterproof layer people think it is...code requires a waterproof liner that is SLOPED underneath the tile, not flat on the floor. It is the primary waterproofing...the tile is decorative. If your liner is flat, eventually, all of the cement under the tile will end up being saturated. After awhile, the pH will change with the pollutants from soaps, etc., and that plus the moisture will make the shower start t osmell like a swamp of rotting organic material.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3

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    It is just my opinion in that mold could grow pretty much anywhere it is damp and airless.

    I had a problem with my bathroom a few years ago, but, my insurance company covered a lot of it. They brought the walls down, the floor up, removed the toilet, vanity and sink, etc, all but the tub where there wasn't any problem. They paid for and brought in restoration services, an air-scrubber and a dehumidifier which it all ran for almost a month. Now, I do have pretty extensive health problems, which included pneumonia at the time, so, I am not sure if my health problems weighed any on there decision or not. You might want to at least ask or read your policy.

    They also paid for the new flooring, the wallpaper, the vanity, the sink, etc, the only non-paids were the toilet, and the plumber.

    I do wish you good luck, nothing more miserable than mold or not being able to find even, the problem.

  4. #4
    In the Trades maintenanceguy's Avatar
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    Mold needs two things. Food and water. In fact, anywhere that has food and water WILL have mold.

    Mold food is any organic material. I've taken a couple of mold remediation classes. The instructor would say that "even old mold with bad teeth" could live on the kind of organic crud you're describing.

    There is no way to get rid of the mold. You can clean the drain frequently and probably keep it at bay but it will always come back because there will always be food and there will always be water.

  5. #5

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    Thanks everyone for your replies. What is weird is that when the old concrete was removed the smell went away. We had to wait an entire week for a new drain part to be delivered (it was an odd size) and all that time where only the drain pipe and the wood subflooring was visible, there was no smell. It wasn't until the new concrete was poured in that the smell returned. Maybe the smell was escaping into the area below the wood, but now it has no place to go but up into our airspace?

    Another thing, I also got pneumonia right when this smell first occurred. I was in the hospital for days. I didn't link the two together because the smell didn't arrive until after I recovered, but it was just a few days later.

    So now I don't know what to do. I've poured some bleach into the trap to try and kill some of the fungus or whatever it is. I can take a wire brush and clean it too. Any other thoughts?

    My plumber said that in order to replace the trap entirely that he'd have to go in through the living room ceiling below. $$$$ Of course we'd also have to take out the brand new concrete that was just put in.

    I just want the smell to go away!!

  6. #6
    Remodel Contractor GabeS's Avatar
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    Are you sure the trap is completely filled with water? If a trap is not vented properly it can siphon until the seal breaks. There will still be water in the trap, but there will be just enough space for the sewage smell to pour into the room. It doesn't matter that you are on the second floor. The smell will travel.

    Also, as jadnashua was saying, when you did you shower floor over did you do the whole thing over or just the top cement layer and tile?

    There are two layers of cement. The more important one is under the liner and that layer is sloped towards the drain(thus the name "preslope"). When water gets through the tile and upper cement layer it hits the liner and because of the preslope the water travels to the drain which has weep holes(these MUST not be clogged) to allow the water to escape. If you have no preslope the water will just sit there (not a good thing). You need to have a professional tile person do this work. (No offense to anyone, but some tilers think that some plumbers do not construct the preslope and liner properly and this part should be left to the tiler).

    Everyone has that hair and crud you are talking about, not just you. So I doubt that is what's causing the smell.

    Also, do you have 1 1/2" pipe or 2"? 2" is better and I believe required for showers.
    Gabe

    Don't follow my advice, I only know a thing or two about a thing or two.

  7. #7
    Plumber Cass's Avatar
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    There is a good chance that the trap arm is level or pitched back. If it is this would cause the line to build up a layer of gunk, over time, that will always cause the trap water to smell.

    If you can find a plumber with a camera small enough to navigate a 2" trap you could see if that is so...If you can find a 2", very flexible brush, you may be able to clean the pipe out...I am going to guess that the plumber had a rag in the pipe while you were waiting for the part...this may account as to why the smell went away then came back...

  8. #8

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    Hi Gabe,

    We have a 2" pipe and it seems to be filled with water all the way, although I have to look kind of far down to see it.

    As of right now we only have that initial layer of concrete poured. And it was done by the tile guy and it definitely angles towards the drain, down from the walls. I don't know though about the weep holes. The concrete entirely encompasses the drain pipe, which sticks up in the air a few inches. Obviously it's not a water-tight seal with the concrete around the drain pipe. If water gets in there it would seemingly run along the outside of the pipe to where I'm guessing the weep holes are.

    I think we may have to rip out the new concrete and replace the trap, huh? I'm pissed because my plumber was either trying to save us money by NOT replacing the trap, or he just didn't want to tackle a job that would require going through the ceiling below the shower (even though my tile guy said he'd only have to pull up the wood sub-flooring in order to replace the trap -- so I don't know what to believe). I'm not knocking our plumber, because he's a good guy in every way, he just seems kind of young so maybe he hasn't experienced this issue before.

  9. #9
    Remodel Contractor GabeS's Avatar
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    Shower construction has to be done a certain way for it to last and work properly. There are a few different ways to do it.

    If you are using CPE liner, you have to use a three piece drain assembly. First you do the preslope up to the edge of the first drain assembly. The liner goes over the entire drain and small slits are cut to expose the four bolts for the next drain piece. The hole is cut for the drain and the membrane is siliconed to the lower drain around the drain opening. When the top layer of cement is poured you have to put pebbles or tile spacers over the weep holes so the cement doesn't clog them. After the top layer of cement dries you install your tile(some people do this in one step "wet set").

    Schluter makes some great shower systems as an alternative to traditional method.

    Go to tileyourworld.com forum and go to the liberry section to understand proper shower construction. I don't know if this part of the shower is what's causing the smell, but in either case it still has to be done properly. Now's your chance to inspect it before it's finished.

    Cass raising an interesting point, but if used daily the water in the trap would be replaced with every use.
    Gabe

    Don't follow my advice, I only know a thing or two about a thing or two.

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