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Thread: Installing a pedestal sink. Help needed.

  1. #1

    Default Installing a pedestal sink. Help needed.

    Hello,

    I am wondering if it is possible to install a pedestal sink when the water supply lines come up through the floor instead of out through the wall? Everything I have seen has the wall lines. Any advice would be greatly appreciated.




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

    The water lines are okay, the "S" trap isn't legal, and it may be in the way of the pedestal if you insist on using it.

  3. #3

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    What is needed to replace the s trap and make it legal? That was what the previous owner had installed.

    If these lines will work how difficult would it be to change them to new since I'm quite sure that they will be exposed somewhat?

  4. #4
    Plumber jimbo's Avatar
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    Default

    Ideally, all those pipe would be inside the wall, and I assume there is some reason why they are not. The water pipes could be painted white. The problem with the S trap is (a) code doesn't like them because they can easily be siphoned dry. (b) it probably puts the trap too far out from the wall to connect to a pedestal sink. Maybe if you get a very large pedestal sink, it would work.

  5. #5

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    The pipes are not in the wall because the house was built in 1931. I guess. I would love them to be in the wall, but they aren't and this is not the time to put them there.

    The s trap does not work with the sink at all. It is too large and I really don't want it if it is not to code. What is supposed to be there instead?

    Thanks for the help.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    All traps are supposed to have a vent...yours does not. The vent is to prevent the trap from being siphoned dry. To do it right, you'd have to have a pipe going up to connect to the vent going to the roof...the arm from the output of the trap would go to the drain with a santee, and up to the vent. The t, vent and drain would normally be in the wall.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  7. #7

    Default Pedestal sink

    Don't be discouraged!

    I installed a pedestal sink in nearly the same situation as yours several months ago, and I'm very happy with the result. My house was built in the late 1920s and, like yours, it has the supply and drain lines in the floor rather than the wall.

    I used a chrome s-trap from the hardware store and an American Standard Williamsburg pedestal sink from a local big box store. As I recall, there's reasonable amount of adjustability in the sections of the s-trap, so you have some leeway if you're willing to live with a sink that might not be absolutely centered on the drain or supply line.

    The fact that the pedestal base does not hide all of the lines does not bother me at all. In fact, I think most vanities are ugly, and since they're commonly made from some sort of particle board, they can become sources of odor and or mold. Pedestals are a much nicer option.

    My logic is that since you're not adding or even moving an existing fixture, your code compliance is grandfathered. I don't think most code officers would make you rip open a wall to connect to a vent line for this project. I'm sure that there is a vent stack somewhere close by that has worked fine for almost 80 years.

    I'll post a few photos tomorrow, if I can find the batteries for my camera.

    Good luck!

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Default bob in maine

    My logic is that since you're not adding or even moving an existing fixture, your code compliance is grandfathered. I don't think most code officers would make you rip open a wall to connect to a vent line for this project. I'm sure that there is a vent stack somewhere close by that has worked fine for almost 80 years.

    Codes, lack of codes, grandfathering in, or anything else cannot change the physical laws that preclude using "S" traps. They will ALWAYS siphon themselves every time the sink is used. THAT is a physical law. There could be a functional vent right next to that sink, but it would do NOTHING to make the "S" trap acceptable. The only thing that grandfathering it in would do is not make it any worse than it has been since it was installed and if they have lived with it that long then maybe they can handle it.

  9. #9

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    Quote Originally Posted by hj View Post
    The only thing that grandfathering it in would do is not make it any worse than it has been since it was installed and if they have lived with it that long then maybe they can handle it.

    What are we living with exactly? I'm not being facetious, I honestly am not understanding the siphoning dry and what the problem is here. The previous sink worked just fine. There were no issues with it.

    Bob in Maine, I would love to see pictures.

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    The normal water in the trap is what blocks sewer gasses, bugs, rodents, etc. from exiting from the drain into the house. Sewer gasses can be a health hazard...it just depends on their concentration. Part of the outgassing from decomposition is methane, which is also flamable, but would have to be just in the right concentration to do that. Possible, but improbable.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11

    Default

    As I understand it, the water that sits in the low bend of the s-trap acts as a plug, preventing sewer gas from rising up your vent stack and into your bathroom by way of the sink drain pipe.

    The concern is that this plug of water can be removed by the pressure created by moving water rushing out of the basin and through the drain pipe or by little burps of air driven by back pressure. This water plug can also dry up if you don't use the sink for long periods of time.

    I absolutely agree that there are better more modern types of traps available that codes and common sense require us to use in new construction or major renovation.

    However, I don't agree with hj's position that fundamental physics dooms all s-traps in all installations to failure. These were invented and refined by smart people over a long period of time, and were installed for many, many years until better methods were developed.

    For some minor alteration like replacing one sink basin with another, leaving well enough alone is not a bad choice, as long as the existing condition is not hazardous.

    By the way, the same issues apply, whether you plan to replace the existing basin with a pedestal or a vanity-mounted lav.

    I'll try to take pictures of my sub-standard but probably good enough installation this evening.

  12. #12

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    Thank you for your explanations. I appreciate it. We have no had any issues like that. I hope our luck continues.

  13. #13
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default

    Quote Originally Posted by midge View Post
    I would love them to be in the wall, but they aren't and this is not the time to put them there.
    Au contraire, what better time, than now? Do it before you get your pretty sink installed, so that you don't have to uninstall it later.

    Having said that, I understand you're not in the mood for a major demolition job, but it might not be all that bad. You could also consider boxing in a thin chase to allow a vent to rise behind the sink without totally destroying the wall. What do you know about the existing plumbing, anyway? What is above, and below, this room?

  14. #14

    Default

    Well Mikey,

    Now is not the time because we just finished doing battle with the walls that the walls almost won. There is no way that the beadboard that nearly killed us is getting torn up. We thought we were being clever doing the walls with the sink out of the way. Yeah right. Had we known more about what was needed for the pedestal sink we could have easily taken care of that before doing the beadboard.

    The basement is below this bath and a balcony is above it.

    Plus in the course of working in here we discovered that the toilet flange was loose and has been slowly rotting the subfloor. So we have already had major unexpected demolition. All I wanted to do was get rid of the fugly wallpaper.

  15. #15

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    Here are some pics of our pedestal sink. I just replaced the old pvc s-trap and braided supply lines that were inside the moldy old vanity with chrome.

    As you can see, the stubs through the floor are copper, not pvc like yours. I choose to see the scaley old copper as rustic, instead of unfinished.

    Wainscoting, toilet and ct floor were also part of this project.
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