# Why does my building's water smell like marijuana? **URL:** \ **Category:** Factual Questions\ **Created:** [April 21, 2011, 4:58pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250 "2011-04-21T16:58:03Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![TwoCoasts](https://avatars.discourse-cdn.com/v4/letter/t/5e9695/32.png) [@TwoCoasts](https://boards.straightdope.com/u/TwoCoasts)\ **Post date:** [April 21, 2011, 4:58pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/1 "2011-04-21T16:58:03Z")
Some mornings when I turn on the shower, the water has a faint but distinctive odor. You might say it resembles peat, but let’s be frank: it smells like grass. No, not the kind you grow in the front lawn. My apartment is in a high-rise building in Manhattan, so the municipal water supply mainly comes from reservoirs in the Catskills. A lot of folks up there might own bongs, but even if they all simultaneously dumped a year’s worth of bong water into the reservoirs, I doubt it would be enough to make the water smell. And I vaguely recall occasionally noticing the same thing when I lived in another high-rise in Jersey City, NJ, which I think uses a different water supply [fill in your favorite New Jersey joke here]. So what’s the source of this phenomenon? Something growing in the reservoirs? Water treatment plants? The building water system? Should I be worried? Should I be extremely relaxed? Thanks for any insight. ---
**Author:** ![Full\_Metal\_Lotus](https://avatars.discourse-cdn.com/v4/letter/f/df705f/32.png) [@Full\_Metal\_Lotus](https://boards.straightdope.com/u/Full_Metal_Lotus)\ **Post date:** [April 21, 2011, 5:12pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/2 "2011-04-21T17:12:51Z")
Its not the water supply. Its the drains. Other people in your building are smoking dope, and its being sucked into the vents off the drain system (the overflow on your tub) and then the steam pressure of your drain water going down drain forces the odours from other apartments up through the vent hole. In a tall building, the vents from the overflow are connected to a common stack pipe. This prevents vacuum lock on the drains, but can also let odours from other apartments sometimes cross ventlate. ---
**Author:** ![TwoCoasts](https://avatars.discourse-cdn.com/v4/letter/t/5e9695/32.png) [@TwoCoasts](https://boards.straightdope.com/u/TwoCoasts)\ **Post date:** [April 21, 2011, 7:13pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/3 "2011-04-21T19:13:39Z")
That does make sense. I don’t know much about plumbing, but I assume the vent pipe explanation would apply even if the plumbing fixture doesn’t have an overflow like a tub (that I’m aware of): e.g., a standalone shower stall, or a kitchen sink? Also interesting that I’ve never smelled ordinary cigarette smoke. Which may just tell us that NYC now has more dope smokers than cigarette smokers. ---
**Author:** ![voltaire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voltaire/32/313_2.png) [@voltaire](https://boards.straightdope.com/u/voltaire)\ **Post date:** [April 21, 2011, 9:15pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/4 "2011-04-21T21:15:03Z")
Look on the bright side, next time you take a bath, you can help yourself to a monster toke off your tub’s overflow vent. 😛 (A soak & toke!) P.S. Yesterday was 4/20, so I wouldn’t be surprised if the smell was more pronounced than usual. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [April 21, 2011, 9:18pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/5 "2011-04-21T21:18:03Z")
> [@Full\_Metal\_Lotus](#): > > Its not the water supply. Its the drains. Other people in your building are smoking dope, and its being sucked into the vents off the drain system (the overflow on your tub) and then the steam pressure of your drain water going down drain forces the odours from other apartments up through the vent hole. > > In a tall building, the vents from the overflow are connected to a common stack pipe. This prevents vacuum lock on the drains, but can also let odours from other apartments sometimes cross ventlate. If odors from the vent stack can get into the apartment the OP has a _major_ plumbing issue. Major, as in, needs to be dealt with yesterday since that would imply that sewer gas is also entering the apartment. I don’t think that’s the case though since the over flow from the tub is separated from the stack by the tub’s trap. ---
**Author:** ![VinylTurnip](https://avatars.discourse-cdn.com/v4/letter/v/b2d939/32.png) [@VinylTurnip](https://boards.straightdope.com/u/VinylTurnip)\ **Post date:** [April 21, 2011, 9:37pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/6 "2011-04-21T21:37:50Z")
> [@Full\_Metal\_Lotus](#): > > Other people in your building are smoking dope, and its being sucked into the vents off the drain system (the overflow on your tub) and then the steam pressure of your drain water going down drain forces the odours from other apartments up through the vent hole. Wake & bake, eh? ---
**Author:** ![Al\_Bundy](https://avatars.discourse-cdn.com/v4/letter/a/e79b87/32.png) [@Al\_Bundy](https://boards.straightdope.com/u/Al_Bundy)\ **Post date:** [April 21, 2011, 9:49pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/7 "2011-04-21T21:49:30Z")
It may be from the venting system somehow, not the drain vents as posted elsewhere because the water in the traps prevents backflow there. The air vents such as ceiling fan venting often co-mingle air from other units. My guess would be the unit above you is connected to the same vent. A floppy vent seal is made to stop air from backing up into your unit, but I believe that is not working. You could test my theory by taping over the entire vent (with the fan off) and take a shower with the door open to prevent condensation. ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [April 22, 2011, 1:15am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/8 "2011-04-22T01:15:54Z")
I would doubt that the oder is comming from the vent piping. A cracked or broken vent pipe can cause an smell in a building, but it is not like any MJ I have ever been around. It is more like a pit toilet that has rippend in the sun on a hot summer day. The bathroom vent? Depending on the buildings duct system. If it is a common duct with one exhaust fan on the roof and if your building has extream pressure differances between floors caused by poor return air systems it is possable to get a back flow. If your bathroom has it own exhaust fan then I would doubt that as source. Some high rise buildings use water tanks. If someone is dropping something in the tank then it may be possable. Another thought someone smoking on the roof near the fresh air intakes? ---
**Author:** ![Waffle\_Decider](https://avatars.discourse-cdn.com/v4/letter/w/77aa72/32.png) [@Waffle\_Decider](https://boards.straightdope.com/u/Waffle_Decider)\ **Post date:** [April 22, 2011, 2:10am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/9 "2011-04-22T02:10:02Z")
Heh, the maintenance crew at the building of my former workplace had a habit of smoking pot on the roof. If the wind was blowing just right, that sometimes made the whole office smell like pot too. Funnily enough, that happened on the day a journalist came to do an article on our company. I guess she found out what made us tick. 😃 ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [April 22, 2011, 3:22am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/10 "2011-04-22T03:22:29Z")
> [@voltaire](#): > > … > > P.S. Yesterday was 4/20, so I wouldn’t be surprised if the smell was more pronounced than usual. 😕 ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [April 22, 2011, 3:43am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/11 "2011-04-22T03:43:31Z")
> [@Leo\_Bloom](#): > > 😕 > **[420 (cannabis culture)](https://en.wikipedia.org/wiki/420_%28cannabis_culture%29)** > > This is an accepted version of this page > > > > 420, 4:20 or 4/20 (pronounced four-twenty) is cannabis culture slang for cannabis consumption, especially smoking around the time 4:20 p.m. (16:20). It also refers to cannabis-oriented celebrations that take place annually on April 20 (4/20 in U.S. date form). > Five high school students in San Rafael, California, coined the term as part of their 1971 search for an abandoned cannabis crop, based on a treasure map made by the grower. Calling themselves ... ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [April 22, 2011, 3:51am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/12 "2011-04-22T03:51:45Z")
> [@Washoe](#): > > [420 (cannabis culture) - Wikipedia](http://en.wikipedia.org/wiki/420_%28cannabis_culture%29) Thanks. For me, it happened to have been a serendipitous event…😃 ---
**Author:** ![Washoe](https://avatars.discourse-cdn.com/v4/letter/w/ecae2f/32.png) [@Washoe](https://boards.straightdope.com/u/Washoe)\ **Post date:** [April 22, 2011, 3:58am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/13 "2011-04-22T03:58:23Z")
You’re welcome. I had to explain it to my mother once too. She saw a bumper sticker that said “warning—this car stops at 4:20.” She asked me what it meant. I told her that it’s a signal to the cops to pull the car over and toss it. ---
**Author:** ![Eyebrows\_0f\_Doom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eyebrows_0f_doom/32/3119_2.png) [@Eyebrows\_0f\_Doom](https://boards.straightdope.com/u/Eyebrows_0f_Doom)\ **Post date:** [April 22, 2011, 6:32am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/14 "2011-04-22T06:32:30Z")
> [@TwoCoasts](#): > > My apartment is in a high-rise building in Manhattan, Holy crap. I also live in Manhattan and I’ve noticed the same thing! :eek: I’m not joking! There have been several times when the inside of the dishwasher smells distinctly like marijuana after I run the wash cycle. 😕 ---
**Author:** ![EvilTOJ](https://avatars.discourse-cdn.com/v4/letter/e/ee59a6/32.png) [@EvilTOJ](https://boards.straightdope.com/u/EvilTOJ)\ **Post date:** [April 22, 2011, 10:11am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/15 "2011-04-22T10:11:29Z")
Is the smell like a “Dude I just opened a fresh baggie?” or “Man, this smoke smells awesome!”? Also, are you sure it’s actually a marijuana smell, or is it a skunk smell? It’s possible you have a mold problem somewhere. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [April 22, 2011, 12:39pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/16 "2011-04-22T12:39:10Z")
“Hey, dude, someone plumbed our bong into the shower!” ---
**Author:** ![TwoCoasts](https://avatars.discourse-cdn.com/v4/letter/t/5e9695/32.png) [@TwoCoasts](https://boards.straightdope.com/u/TwoCoasts)\ **Post date:** [April 28, 2011, 8:48pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/17 "2011-04-28T20:48:58Z")
Thanks, Eyebrows, nice to know I’m not the only one who’s noticed this. Re. EvilTOJ’s questions, it’s been a while since I smelled a fresh baggie, but I’d say this smells more like the smoke than the fresh stuff. Now that I think about it, the fact that I’ve never smelled cigarette smoke or any other outside odors in the same bathroom makes me question both the air vent and plumbing vent theories–if airborne odors were getting sucked into the bathroom via either type of vent, you’d think I would smell other odors, too, not just this one, right? Also, I sealed up the air vent in the bathroom to avoid heat loss this winter–although the seal may not be perfect–but still smell it. Doesn’t smell like skunk or mold to me, either (both odors with which I am, unfortunately, pretty familiar. And I’ve gotta say I’ve never understood the idea that skunk and weed smell similar. At least not any skunk, or any weed, that I’ve ever smelled). So I’m still puzzled and open to ideas. The common theme I notice in both Eyebrow’s observation and mine is steam from hot water building up in an enclosed space (dishwasher, shower stall). ---
**Author:** ![Full\_Metal\_Lotus](https://avatars.discourse-cdn.com/v4/letter/f/df705f/32.png) [@Full\_Metal\_Lotus](https://boards.straightdope.com/u/Full_Metal_Lotus)\ **Post date:** [April 29, 2011, 8:36am UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/18 "2011-04-29T08:36:16Z")
I thought about the singularity of pot smell too. It seemed odd that you didn’t smell cooking, cigarettes, perfume, incense and the myriad other smells of people. The thiols that make the skunky smell of pot are common to quite a few molds and fungi, so it may be a drain/mold issue. An earlier poster was correct about the p-trap on the drain, btw. The only other thing I can think of is that a pressure differential is created when you have running water down the drain and the vacuum it creates is “answered” via your bathroom fan vent. If one of your neighbours is toking in the boysroom, it could be an answer to your scenario. To the poster with the 4:20 dishwasher… skunky smell in a dishwasher usually meand trapped bone or cartiledge in the solids filter. Try a empty run with bleach (Or TSP - NOT BOTH\>\>\>FUME RISK)after cleaning it out (check your manual). ---
**Author:** ![omiksy](https://avatars.discourse-cdn.com/v4/letter/o/977dab/32.png) [@omiksy](https://boards.straightdope.com/u/omiksy)\ **Post date:** [March 17, 2014, 7:15pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/19 "2014-03-17T19:15:28Z")
Hey i felt the need to post here. I moved into an apartment in nyc a few weeks ago and the bathroom stunk of weed so badly we had to keep the door shut and the bathroom window open. we do not smoke. I found this site early on and figured someone in the apartment was a super pot head. but it was getting so bad i almost called the landlord. I found another site to day that said bathmats give off the smell for weeks or months after you buy them. sure enough the bathmat the land lords put in there to make it look nice is like super weed air freshener. just thought this might help someone looking. even though its an old thread and the people on here probably got past the odor phase of the bathmat by now. other may not have. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [March 17, 2014, 7:59pm UTC](https://boards.straightdope.com/t/why-does-my-buildings-water-smell-like-marijuana/579250/20 "2014-03-17T19:59:26Z")
Maybe someone is using the building’s water tower as a gigantic bong.