# Plumbing and Science. **URL:** \ **Category:** Factual Questions\ **Created:** [May 25, 2015, 2:48pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796 "2015-05-25T14:48:46Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [May 25, 2015, 2:48pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/1 "2015-05-25T14:48:46Z")
The waste pipe from my kitchen sink is a bit slow. It drains, but not as fast as the cold water tap can fill it. If, however, I get a vortex going by running the water down the side of the bowl (swivel tap) it drains away fast. Why? ---
**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:** [May 25, 2015, 3:02pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/2 "2015-05-25T15:02:24Z")
Does it gurgle when the water is draining? Sounds like it might be a venting issue. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [May 25, 2015, 3:21pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/3 "2015-05-25T15:21:01Z")
I assume that there is some grease or something and will get some gunk to clear it. My question is - Why does it drain more quickly with the vortex? ---
**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:** [May 25, 2015, 3:37pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/4 "2015-05-25T15:37:44Z")
Because it’s a venting issue. The vortex allows the air to “get out of the way” and let the water drain. Without the vortex, the air needs to bubble up. ---
**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:** [May 25, 2015, 4:21pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/5 "2015-05-25T16:21:12Z")
> [@bob\_2](#): > > I assume that there is some grease or something and will get some gunk to clear it. My question is - Why does it drain more quickly with the vortex? You could, if it can be done easily, pull the trap off and see if there’s any build up in there. I’ve had to do that from time to time. Build up will slow it down and grease build up is easily cleaned out by hitting it with a garden hose sprayer (outside). ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [May 25, 2015, 6:15pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/6 "2015-05-25T18:15:42Z")
> [@beowulff](#): > > Because it’s a venting issue. > The vortex allows the air to “get out of the way” and let the water drain. > Without the vortex, the air needs to bubble up. You don’t need a kitchen sink. You get the same effect with a 2L soft drink bottle. Fill it up and pour it, it goes glug-glug-glug. Swirl the contents while draining to get a whirlpool and it will drain faster, as the air and water change places simultaneously. Once when I was young and foolish I used to drain grease down my kitchen sink, probably without enough detergent - until the day it would not drain any more. Somewhere down the pipe where it cooled off, the grease built up and clogged the pipe. A pipe snake treatment followed by treatments with Drano was needed to get the water flowing again. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [May 25, 2015, 7:18pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/7 "2015-05-25T19:18:34Z")
> [@md2000](#): > > You don’t need a kitchen sink. You get the same effect with a 2L soft drink bottle. Fill it up and pour it, it goes glug-glug-glug. Swirl the contents while draining to get a whirlpool and it will drain faster, as the air and water change places simultaneously. … Not sure that is an analogous circumstance. The issue in the 2L bottle circumstance is that the loss of liquid creates an increasing pressure differential with greater air pressure on the outside than the inside of the bottle, until the relatively higher outside pressure is greater than the pressure of the inside air and the water and air enters the bottle. In the sink circumstance the pressure above stays at atmospheric the whole time. If you poked a hole in the top of the soda bottle to replicate then the air and water changing place at the same time would be immaterial. I am not sure what the answer is but if “venting” is that then the answer seems to be a fail. I am _guessing_ that a vortex minimizes the impact of resistance on the outermost ring relative to laminar flow through a tube, but defer to those with the physics chops to tell me if my guess in on target. The way I’d image it is that in laminar flow the outermost cylinder of fluid is not moving at all and each cylinder inward flows a bit faster … a narrowing in the tube therefore restricts flow quite a bit. A vortex is turbulent and does not have that more static outer ring. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [May 25, 2015, 7:29pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/8 "2015-05-25T19:29:27Z")
You seem to be confused about how venting works in a waste system. In your example, the hole poked in the soda bottle _is_ the vent. It lets air in. That’s what vents do. If your sink’s vent pipe is clogged or blocked or installed improperly, you will see the symptoms described by the OP. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [May 25, 2015, 7:40pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/9 "2015-05-25T19:40:53Z")
I readily admit I do not have a mastery of plumbing nor of physics and may be confused but my limited understanding is that the vent is not on the intake side of the trap (analogous to holes in the soda bottle) but distal to the trap - to allow venting of sewer gases and equalizing of pressure so that water will remain in the trap. Is the proposed explanation that a column of water is creating a relatively increased air pressure distal to the trap and that the vent allows that to stay at atmospheric … hence our op’s slow flow is not due to a clogging in the pipe but a clogged vent stack? ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [May 25, 2015, 7:44pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/10 "2015-05-25T19:44:04Z")
> [@DSeid](#): > > I readily admit I do not have a mastery of plumbing nor of physics and may be confused but my limited understanding is that the vent is not on the intake side of the trap (analogous to holes in the soda bottle) but distal to the trap - to allow venting of sewer gases and equalizing of pressure so that water will remain in the trap. It does both. The vent is there to allow air in behind the slug of water moving through the trap, and to vent sewer gas out of the building. > [@](#): > > Is the proposed explanation that a column of water is creating a relatively increased air pressure distal to the trap and that the vent allows that to stay at atmospheric … hence our op’s slow flow is not due to a clogging in the pipe but a clogged vent stack? Right. Clogged vents are a pretty common problem and the symptom is almost always a slow, glugging drain. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [May 25, 2015, 7:46pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/11 "2015-05-25T19:46:32Z")
If such is the answer then our op will be able to tell us either that it has always been like this (improperly installed) or that minimally that snaking it out fails to fix the problem. Assuming that snaking it out fixes it (therefor not a clogged vent) - is there any way that a vortex will flow better down a partially clogged drain than not? Or is the fact that the vortex flows faster _diagnostic of_ a venting issue? ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [May 25, 2015, 8:15pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/12 "2015-05-25T20:15:21Z")
The presence of a vortex at all is strong evidence of a venting problem. With a properly functioning vent, you should never get a vortex because enough air will be provided by the vent to equalize the pressure, and the draining water will go straight down, even if one imparts significant spin. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [May 25, 2015, 11:26pm UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/13 "2015-05-25T23:26:04Z")
Huh. Strikes me as odd since I can’t remember a tub or bathroom sink draining quickly without a vortex if draining quickly. I guess I’ve always had venting problems and never knew … **bob++** do let us know if you get your sink draining better with a snake or such. If if cannot then the venting issue would likely be your answer both for the fix and for your question. If it does then I am glad your sink flows better but we are left with my ill-informed speculation regarding the shear stress differences between laminar flow and flow in a vortex as it approaches a narrowing in the conduit. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [May 26, 2015, 12:08am UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/14 "2015-05-26T00:08:20Z")
If I took a garden hose and stretched it out 50 ft and put various curves in it maybe even a couple of ups and downs. Now I pick up one end of the hose and insert a funnel into it that I proceed to pour water in. Will it flow straight down or will it burb. My money would be on flow straight out. I don’t understand how a sewer pipe could develop back pressure without a blockage somewhere. ---
**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:** [May 26, 2015, 12:18am UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/15 "2015-05-26T00:18:52Z")
> [@HoneyBadgerDC](#): > > If I took a garden hose and stretched it out 50 ft and put various curves in it maybe even a couple of ups and downs. Now I pick up one end of the hose and insert a funnel into it that I proceed to pour water in. Will it flow straight down or will it burb. My money would be on flow straight out. I don’t understand how a sewer pipe could develop back pressure without a blockage somewhere. Why don’t you try it. Make sure to put a trap in it… ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [May 26, 2015, 12:24am UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/16 "2015-05-26T00:24:28Z")
> [@beowulff](#): > > Why don’t you try it. > Make sure to put a trap in it… Yes, the water between the trap and the funnel would need to burp. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [May 26, 2015, 2:00am UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/17 "2015-05-26T02:00:46Z")
If the top of the hose is above the top of both sides of the trap then why? (Even if there is not already water in the trap.) Water comes down, reaches a level above the distal top end of the trap and continues to flow seamlessly. FWIW googling for venting and poor draining I find multiple plumbing expert advice sites all of which state that poor venting will not cause drainage problems generally speaking - [for example.](http://terrylove.com/forums/index.php?threads/slow-draining-tub-a-vent-issue.49624/) > [@](#): > > … The vent should come off a the same level as the p-trap. > Not that the draining would improve if you do, but you would stand less chance of siphoning the trap when the tub drained. … The lack of a vent by itself would NOT cause bad drainage, in fact it usually causes the drain to work too good, and that can cause odor problems. … Even distal to the trap an improperly working vent should only result in positive pressure if there is some sort of obstruction distal to it. (And negative pressure distal of the trap won’t cause poor drainage in the sink although it certainly would cause bubbling or burping .) ---
**Author:** ![Kiwi\_Fruit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kiwi_fruit/32/12_2.png) [@Kiwi\_Fruit](https://boards.straightdope.com/u/Kiwi_Fruit)\ **Post date:** [May 26, 2015, 4:21am UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/18 "2015-05-26T04:21:57Z")
> [@DSeid](#): > > Even **distal** to the trap I’m not sure that word means what you think it does. Most references indicate it to mean the furtherest point from (an attachment, tendon on a bone). What do you think it means? ---
**Author:** ![Inner\_Stickler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inner_stickler/32/318_2.png) [@Inner\_Stickler](https://boards.straightdope.com/u/Inner_Stickler)\ **Post date:** [May 26, 2015, 4:41am UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/19 "2015-05-26T04:41:03Z")
He’s using it to mean the part of the plumbing farther from you vis a vis the trap. So the plumbing between the basin and the trap is proximal and the plumbing between the trap and the stack is distal. But if you were on the roof messing with the stack, they’d be reversed. ---
**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:** [May 26, 2015, 4:43am UTC](https://boards.straightdope.com/t/plumbing-and-science/720796/20 "2015-05-26T04:43:15Z")
> [@HoneyBadgerDC](#): > > If I took a garden hose and stretched it out 50 ft and put various curves in it maybe even a couple of ups and downs. Now I pick up one end of the hose and insert a funnel into it that I proceed to pour water in. Will it flow straight down or will it burb. > [@beowulff](#): > > Why don’t you try it. > Make sure to put a trap in it… > [@HoneyBadgerDC](#): > > Yes, the water between the trap and the funnel would need to burp. Did you just reply to yourself? Or contradict yourself? (A “couple of ups and downs” would be a trap). I’m confused. In the first post you said your money was on it flowing straight down, in the second post you said it would need to burp. If you fill up a funnel with water, my guess is that’ll it’ll go straight down. However, if you fill up a really big funnel, say, one that holds a gallon or two, it’ll start to vortex. They usually take more than a half a cup of water to get started. In your home, as water is flowing down the drain it’s trying to pull air in behind it. Remember, it’s not just one pipe from your sink to the city, there’s a lot of other, air filled, pipes in your house. The slug of water heading down your kitchen is creating a vacuum. The vent stack breaks the vacuum. If the vent is blocked, it’s going to draw that air in from somewhere. It might empty out another trap somewhere and suck air in from that drain. But most likely it’ll make the drain you’re using right now burp/gurgle/vortex since that one is the closest and probably easiest to suck air in from since the water is moving through it. If it can’t do any of that, it’ll just drain slowly. My next guess is that if the funnel experiment does create a vortex, it would be eliminated by adding a vent somewhere in the system (somewhere that makes sense by typical plumbing standards). Add a T and another section of hose going straight up and rising significantly higher than the funnel. Back to the OP, I’m not saying you don’t have a clog, and like I said, you could certainly pull the trap off, that’s an easy place to start and easy for the homeowner to clean. [Next page](https://boards.straightdope.com/t/plumbing-and-science/720796.md?page=2)