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Thread: Do you really need a vent per fixture?

  1. #1

    Question Do you really need a vent per fixture?

    I'm draining a utility sink to a sewage ejector pump. The 1 1/2" drain is dedicated to the sink; there is nothing flowing into it before it reaches the pump basin. The pump basin is vented 2".

    I've heard that each fixture should be vented, but the only thing that could siphon the trap is the pump, and it has a vent. So, do I really need to vent the sink additionally?

  2. #2
    Moderator & Master Plumber hj's Avatar
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    Default vent

    The pump is the least likely thing to siphon the trap, unless it was a perfectly sealed basin, in which case it would be air bound and prevent all drainage into it. The sink can "self siphon" without a vent, and if you do not know why each trap needs a vent, then maybe you should not be doing the plumbing work.

  3. #3

    Default

    Got it.

    Now it seems kind of obvious. It's like when you try to siphon residual gas out of a gas tank: You give a little suck with a bulb on a hose with one end in the tank to get the flow going. Once it starts, as long as the end of the hose stays lower than the gas level, the gas keeps flowing out.

    I guess the same thing happens when water starts flowing from the sink. Without an air inlet in the drain, the water would just keep going until it's all depleted.

    I'll vent the sink.

    Another question: If the sink were close enough to the basin, would the possibility of self-siphoning disappear? Doesn't it have something to do with the outlet of the drain being above the level of the trap? I'm trying to learn here; please don't be discouraging
    Last edited by prashster; 02-24-2006 at 05:48 AM.

  4. #4
    General Contractor Carpenter toolaholic's Avatar
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    Angry ya HJ, DON'T BE DISCOURAGING

    pretty soon they will license, and inspect the trade.

    Martha STEWART has a plumbing primer at amazon books.

    walks you through plumbing units,trap line lenghts ect. 2 hr read and you're ready to contaminate all the drinking water in your hood.

    when a person doesn't have a basic understanding of plumbing ,it's best to discourage them, for the HEALTH of the neighbors

  5. #5

    Default jeez!

    I'm just trying to get some help here.
    I have a little more than a basic understanding of how plumbing works. I know enough to not do something before I fully understand it. That's why I ask questions in this forum.

    Really, it's hard to interpret witty sarcasm via a message board. Your responses come across as mean-spirited. I hope you meet the same attitude when you try to learn about something you're not experts in.

    I wouldn't even mind so much mind the insinuations that I have no business messing around with this stuff, if someone at least first answered my question.

  6. #6
    Forum Admin, Expert Plumber Terry's Avatar
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    Default

    Are you saying the lav drain is at the same level as the waste line to the pump basin?

    If that were the case, and the inlet was always above the water level in the basin, and the basin was vented, then maybe the trap on the lav would not siphon.

    I've never seen a situation in real life like that though.

    If the plumbing were to be inspected, and thank God most plumbing in the US is, they would expect the vent to be done properly.

    Fittings and pipe don't cost very much. It would take less money and time to install the vent, then the time it takes to write the explanation for why it's needed.

    Here is a nice link showing some ways of plumbing a basin with pump.
    I don't care for the use of fittings they chose in the drawing, but you can get some ideas from it.
    http://www.terrylove.com/pdf/qwik%20...structions.pdf

  7. #7

    Default

    thanks a lot

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default vents

    Part of the problem is that many people interpret plumbing as a simple drain pipe that has to flow downhill, and a water pipe is something that runs from point A to point B. Vey simple, and anyone can do that. As long as the trap has a valid air source above the level of the water in the trap it will not siphon, but there are possibly five other forces you could introduce to make the trap lose its seal besides siphonage, and that is what makes a plumber more than a handyman.

  9. #9
    General Contractor Carpenter toolaholic's Avatar
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    Default I apoligize, I was mean spirited

    have to work on that! HJ said it well , with out the sting!

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