# Does a bathroom washbasin need a U-bend? **URL:** \ **Category:** Factual Questions\ **Created:** [November 6, 2023, 12:48am UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659 "2023-11-06T00:48:24Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [November 6, 2023, 12:48am UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/1 "2023-11-06T00:48:24Z")
Title is the question. I recently had a plumber in to fix my bathroom washbasin. He did a bad job, with a lot wrong, which I won’t list here. One thing is, there’s no sign of a U-bend or other trap. I’m not a plumber but that looks wrong to me. My kitchen sink has one. I could be wrong. Maybe it’s not necessary for a bathroom basin. So, plumber-Dopers, is this an error or not? How bad are we talking? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [November 6, 2023, 12:53am UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/2 "2023-11-06T00:53:49Z")
All drains need a trap. P-traps are required by code now, I think. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [November 6, 2023, 1:23am UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/3 "2023-11-06T01:23:07Z")
> [@Peter\_Morris](#): > > So, plumber-Dopers, is this an error or not? How bad are we talking? The P-trap prevents sewer gas from coming back up through the drain. You’ll figure out why that is important pretty shortly if you haven’t already. You’ll certainly want to get that rectified as well as any other deficiencies that might result in a leak or blockage. Stranger ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [November 6, 2023, 1:28am UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/4 "2023-11-06T01:28:18Z")
> [@Stranger\_On\_A\_Train](#): > > The P-trap prevents sewer gas from coming back up through the drain. This. All drains need a trap and a vent. (I.e. a pipe up to the roof not too far away from the drain) I occasionally run across problems in winter when a roof vent freezes and flushing or draining a large sinkful causes gurgling in nearby fixtures, because the water is sucking air - and water - from other traps. I also have the problem that during very dry winter, i have to run the water in the no-regularly-used basement bathtub occasionally, or the trap dries out enough and I start to smell sewer stink downstairs. ---
**Author:** ![TreacherousCretin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/treacherouscretin/32/476_2.png) [@TreacherousCretin](https://boards.straightdope.com/u/TreacherousCretin)\ **Post date:** [November 6, 2023, 1:31am UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/5 "2023-11-06T01:31:56Z")
> [@Stranger\_On\_A\_Train](#): > > You’ll certainly want to get that **rectified** … (My bolding) Perfect choice of terminology. We had a shower stall in a third bedroom we never use, and one summer what water there had been in the trap evaporated. The smell of sewage in that part of the house was nose-catching. Ran the shower for a few seconds to refill the trap and the problem was solved. ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [November 6, 2023, 12:46pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/6 "2023-11-06T12:46:56Z")
Code requires a p-trap, as well as venting in some form. Your work was likely done by a “handyman”, not a “plumber”. ---
**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:** [November 6, 2023, 12:57pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/7 "2023-11-06T12:57:20Z")
As stated, it’s wrong. I can’t imagine how a plumber could possibly have not installed one. If this is on your first floor, check your basement and make sure, for some odd reason, the plumber didn’t install it below the floor. In the mean time, until you, or another plumber, get one installed. It might be worth sticking a wet rag over the drain. If for no other reason, to keep the smell contained to the drain (and health/safety reason). ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [November 6, 2023, 1:08pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/8 "2023-11-06T13:08:41Z")
> [@md-2000](#): > > I occasionally run across problems in winter when a roof vent freezes and flushing or draining a large sinkful causes gurgling in nearby fixtures, because the water is sucking air - and water - from other traps. I apologize for the complete hijack, but this is happening in my current (rental) home. Flushing the toilet means a loud gurgle from the bathtub drain. No gurgle means something didn’t, uh, go down all the way, which means you hafta { _sigh_ } wait till the tank refills, possibly plunge a bit, then flush again. So, is this a bad thing? Should I contact my landlord, ask for a plumber? What could they possibly do about it? ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [November 6, 2023, 1:21pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/9 "2023-11-06T13:21:30Z")
Checking the vents from the roof and then using an auger on the toilet (like a snake, but designed for a toilet) is what I’d do. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [November 6, 2023, 1:23pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/10 "2023-11-06T13:23:20Z")
> [@purplehorseshoe](#): > > So, is this a bad thing? Should I contact my landlord, ask for a plumber? What could they possibly do about it? A plumber will check the vent pipe for blockages and clear any with a snake. It’s pretty simple. If it’s only the bath tub it may not mean anything. Bathtub drains and traps can be short, right above the drain pipe. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [November 6, 2023, 1:27pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/11 "2023-11-06T13:27:45Z")
If this is happening now, it probably means the “vent stack” is plugged (seems to early to be frozen - usually that comes from accumulated vapour freezing). On your roof will be one pipes sticking up that are open to the drain system. Otherwise, when you flush, there’s a big slug of water going through the pipe and with no opening to the outdoors it sucks air along with it - if the vent is plugged, it sucks air through the traps in the sink and tub etc. If some strange creature has nested on, or become stuck in, the vent, or leaves have accumulated badly enough on the roof, or, … or… then the vent is plugged. Talk to the landlord and see if they can check it out. Sometimes, to mnimize the number of vents poking up, the plumber will connect the venting from two separated areas with a horizontal run in the attic. If this is done above the insulation, and the piping is not inclined at least a bit to let any rainwater or condensation drain downhill then the horizontal drain could also freeze up.(Or fill with dirt or debris…) Or else the house was plumbed by the OP’s handyman and has no vents… (IANAPlumber, but there’s code requiring vents) ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [November 6, 2023, 1:33pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/12 "2023-11-06T13:33:17Z")
> [@TreacherousCretin](#): > > We had a shower stall in a third bedroom we never use, and one summer what water there had been in the trap evaporated. The smell of sewage in that part of the house was nose-catching. Ran the shower for a few seconds to refill the trap and the problem was solved. With a properly functioning vent stack, you may not get sewer gas entering your living space through a dried-up trap - but that dried-up trap will allow sewer-dwelling roaches to get into your home. Earlier this year I was finding roaches in the 2nd-floor loft in our home. It was about as far from the kitchen as you could get, and there was no food up there to speak of, but I finally figured out that the tub drain in the adjacent bathroom was dried up. Refilled it water, and no more roaches. ---
**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:** [November 6, 2023, 3:28pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/13 "2023-11-06T15:28:21Z")
Obviously just running the water for a few seconds from time to time will keep the trap filled with water. But if you have a drain that’s regularly a problem, they do make devices (Trap Primers) that trickle water down the drain from time to time specifically for this purpose. Also worth noting that if it’s particularly windy out, the venturi effect across the vent stack can draw some of the water out of your traps. At least for me, if it’s been windy all day while I’m at work, the water level in the toilet bowls will often be noticeably lower. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [November 6, 2023, 4:42pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/14 "2023-11-06T16:42:15Z")
Thanks for the replies, everyone. I shall certainly be having words with him about this. > [@kayaker](#): > > Code requires a p-trap, as well as venting in some form. Your work was likely done by a “handyman”, not a “plumber”. Not very handy at that. He is, however, listed in the Yellow Pages under Plumber. > [@Joey\_P](#): > > If this is on your first floor, check your basement and make sure, for some odd reason, the plumber didn’t install it below the floor. I live in a block of flats, ground floor. > [@Joey\_P](#): > > It might be worth sticking a wet rag over the drain. If for no other reason, to keep the smell contained to the drain (and health/safety reason). I’m keeping the plug in the hole. No smells escaping so far. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [November 6, 2023, 4:49pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/15 "2023-11-06T16:49:33Z")
> [@Peter\_Morris](#): > > I’m keeping the plug in the hole. No smells escaping so far. Most wash basins have an overfow hole too. You’d need to plug that. However, installing a trap is pretty simple for a handyman if the drain goes down and then takes a 90° bend to horizontal. ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [November 6, 2023, 4:49pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/16 "2023-11-06T16:49:58Z")
> [@Peter\_Morris](#): > > He is, however, listed in the Yellow Pages under Plumber. Does his advertisement describe him as a “licensed Master Plumber”? It varies by state, but in Pennsylvania someone cannot describe himself as a plumber dealing directly with the public unless he is a licensed Master plumber. Apprentice and Journeyman plumbers can do plumbing work, but have to be employed by a Master plumber. The Yellow Pages do not verify licensure. ETA: a picture would be worth 1,000 words. ---
**Author:** ![FinsToTheLeft](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/finstotheleft/32/2930_2.png) [@FinsToTheLeft](https://boards.straightdope.com/u/FinsToTheLeft)\ **Post date:** [November 6, 2023, 4:58pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/17 "2023-11-06T16:58:43Z")
> [@Peter\_Morris](#): > > Yellow Pages What are these “Pages of Yellow” that you speak of? I just checked and apparently you can still request deliver of the Yellow Pages where I am, but I don’t think I have seen one in person for at least a decade. The White Pages were discontinued by 2010 around here. ---
**Author:** ![doreen](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@doreen](https://boards.straightdope.com/u/doreen)\ **Post date:** [November 6, 2023, 5:03pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/18 "2023-11-06T17:03:08Z")
I don’t know if they are the same companies that used to publish the books, but you can find both the Yellow Pages and the White Pages online. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [November 6, 2023, 5:03pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/19 "2023-11-06T17:03:24Z")
> [@kayaker](#): > > Apprentice and Journeyman plumbers can do plumbing work, but have to be employed by a Master plumber. Unions don’t allow Apprentices to do plumbing work on their own. I’m surprised a Journeyman plumber can’t work independently. [This web site](https://work.chron.com/things-can-journeymans-license-3746.html) says some states don’t allow it. Nothing but a racket for Master Plumbers to take a cut of everything in those states that don’t allow it. I can understand tight regulations for commercial work, or even new construction, but it seems bizarre to prevent a Journeyman Plumber from operating on his own to snake out a drain or vent pipe, or change a faucet. ---
**Author:** ![doreen](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@doreen](https://boards.straightdope.com/u/doreen)\ **Post date:** [November 6, 2023, 5:08pm UTC](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659/20 "2023-11-06T17:08:25Z")
I think that’s pretty common in licensed professions , to be required to either have a license yourself or to be supervised by someone with a license. The alternative is to require everyone to have a license. ETA although I’m not sure snaking a drain or changing a faucet requires a license - or even a plumber at all. [Next page](https://boards.straightdope.com/t/does-a-bathroom-washbasin-need-a-u-bend/992659.md?page=2)