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Thread: Vent problem???

  1. #1
    Engineer Furd's Avatar
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    Default Vent problem???

    Several years ago I replaced my shower with a whirlpool tub. The shower had a 2 inch drain about 4 feet out from the 3 inch house (main) drain. The house drain at the point where the shower drain connected has a 2 inch vent.

    I extended the 2 inch shower drain about another 2 feet and connected a two inch P-trap for the new tub. It has always gurgled when draining although it does not siphon the trap dry. In fact, I did not use this tub for at least a year (may have been close to 2 years) and the trap still had a water seal.

    Should I be concerned about the gurgle? Should I replace the 2 inch trap with a 1-1/2 inch trap or does this need a vent at the trap end? Adding a vent would be a pain in the rear but not impossible.

  2. #2
    Plumber patrick88's Avatar
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    1.5"trap is what should be at the tub but the vent can be within the 6' you have. if you can move it closer i would try to do that. It doesn't need to be at the fixture its just easer most of the time. Can you put it at the 4' point that would be good and maybe easer
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    Engineer Furd's Avatar
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    The 2 inch vent is the main vent on the 3 inch house drain. I can fairly easily change the trap to a 1-1/2 inch model.

    If I remember correctly (it's been a few years since I was in the crawl space), there is a 3x3x2 sanitary tee, or possibly a Y at the end of the house drain (actually the beginning) with a clean out in the run and the side being the vent through the roof. I think, but can't remember for sure, that this vent has (always had) a 2x2x2 sanitary T with the side being the drain from the shower (now tub). I know it is a 2 inch up through the wall and through the roof. I'm pretty sure that the washbasin is vented to this 2 inch with a 1-1/2 line.

    Adding a new vent to the tub would require opening an interior wall and also a new roof penetration because the existing 2 inch vent is through the top plate and not accessible from the attic.

  4. #4
    Homeowner geniescience's Avatar
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    Quote Originally Posted by Furd
    ... It has always gurgled when draining ...
    which one? Both? The opposite one? When it (name it) drains, does that one gurgle? Or the other one (name it)? It is a slurping noise? Or a rumbling gurgle?

    Tell us more about the 2" vent and how far away it is from the 3" connection.

    Did you use a Wye to extend the old 4' long pipe in order to get two P traps on one (now 6' long) arm?

    You can safely leave the 2" trap with the tub. Reducing it to 1.5" changes nothing.

    David

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    Engineer Furd's Avatar
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    What do you mean, "which one? Both? The opposite one? When it (name it) drains, does that one gurgle? Or the other one (name it)? It is a slurping noise? Or a rumbling gurgle?"

    There is only one drain in question, the one from the bathtub. The only other drains in that bathroom are from the toilet (currently sealed with an expanding test plug) and the washbasin. Both the toilet and washbasin are original.

    The bathtub drain replaced the shower that was originally installed. The tub required the drain to be moved further from the main drain approximately 18 to 24 inches. There is no wye on the 2 inch drain from the tub nor are there two traps.

    I don't know the difference between a rumbling and slurping gurgle.

    Maybe I can get down into the crawl space in the next few days and then I can give a detailed account of what is there, maybe even some pictures. I just lifted the hatch and it stinks down there. I'm pretty sure there have been some "critters" in there making a mess.

  6. #6
    Engineer Furd's Avatar
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    Well, I didn't remember it as well as I thought. I was able to take some pictures.

    This is the drain from the tub and the trap.
    http://img.villagephotos.com/p/2006-...775/drain1.JPG

    This is the other end of the two-inch from the trap. It goes into a 2x1-1/2x2 sanitary tee with the top of the tee (1-1/2 inch) going to a 90 then about 18 inches horizontal and 90s up the wall cavity to connect to the two-inch vent through the roof. Going down it connects to a 90 and then a two-inch run to a 3x3x2 wye.
    http://img.villagephotos.com/p/2006-...775/drain2.JPG

    In the next picture you can see the closet drain (3-inch) coming down behind the 2-inch from the bathtub and 90 into a 3x3x? wye with the side going up in the wall to connect to the vent. I didn't notice if this was a 2-inch or 1-1/2 inch vent. You can just barely see the vent (on an angle) to the right of the closet drain, above the 2-inch and beneath the insulation.
    http://img.villagephotos.com/p/2006-...775/drain3.JPG

    Here is a look at the 2-inch where it wyes into the 3-inch. The wye between the clean out and the 2-inch is for the wash basin.
    http://img.villagephotos.com/p/2006-...775/drain4.JPG

    The distance from the tub drain to the sanitary tee (vent) is about 4-feet. The distance from the sanitary tee (vent) to the wye into the main drain is about 5-feet.

    So my question is...should I not be concerned with the gurgle? Is this possibly just the noise of the whirlpool action "scouring" the trap?

  7. #7
    Homeowner geniescience's Avatar
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    does drain2 show a drain pipe rising in height before turning? The way I saw it, is that the top left is where the P trap is, and water comes out from the top left, goes along to the other side of the picture, and then rises before turngin 90 degrees. Is that the way this drain is configured?

    if so, then I will have made up for not figuring out what your first description said.

    david

  8. #8
    Engineer Furd's Avatar
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    No. The top left is the drain traveling towards the main drain. The bathtub trap is to the right of the picture. The flow is from right to left.

    The pipe leaving the top of picture drain 1 is the same pipe that enters from the right side of picture drain 2. That line continues in the foreground of picture drain 3 and enters the main drain (via 3x3x2 wye) in picture drain 4.

  9. #9
    Homeowner geniescience's Avatar
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    all seems well. Can't find a problem.

    Must be a good gurgle.

    david

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    Engineer Furd's Avatar
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    Thank you.

    If no one else sees a problem I will not lose anymore sleep over this, not that I have anyway.

  11. #11
    Homeowner geniescience's Avatar
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    not a red herring, but it is worth mentioning, and only you know how serious the gurgle sounds...
    The vent may be blocked. That part of the tub vent that goes horizontal is more vulnerable. "with the top of the tee (1-1/2 inch) going to a 90 then about 18 inches horizontal and 90s up the wall cavity to connect to the two-inch vent through the roof."

    david

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