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Thread: venting with ejector pit system in basement

  1. #1

    Default venting with ejector pit system in basement

    Hello,

    I had a plumber come out to look at adding a bathroom in my basement. The main drain is above grade, so we're looking at an ejector pit setup. The pit is roughly 30 feet away from the main drain, so we'll have to run the discharge line from the pit about 30 feet. So far, this all makes sense to me.

    The thing the plumber said which did not make sense to me is venting the ejector pit. He said that we would have to run a vent up out the roof from where the discharge line connects with the 4" main drain. This would not be good, as a vent running up from there would have to go through the corner of our living room.

    I don't understand why the vent for the ejector pit cannot run up out the roof where the pit is. Why does it have to vent where the discharge line connects up with the main drain? Anyone care to shed some light on that?

    And is that 30 foot distance between the discharge line and the main drain ok? Is there some sort of max distance to be aware of there?
    Last edited by jiggityjars; 04-08-2008 at 07:14 AM.

  2. #2
    Master Plumber Redwood's Avatar
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    A pit does require a through the roof vent. The air in the pit has to leave as the pit fills with waste and it has to come in as the pit is pumped out. The traps of fixtures also have to be protected by venting. This venting of the pit cannot be accomplished by an AAV (Air Admittance Valve) as it is a one way valve. It is good that your plumber insists on having a through the roof vent.

    How this vent is run can have a lot of variation. Local codes do have bearing on what is allowed. In some areas it may be required to be independent of other vents, while in others it may tie into existing vents. In any case the vent must run pitching back to the pit so that any condensation in the vent or, rain falling in the vent will drain back to the pit and the vent will drain dry. This is a case of there may be many ways to do the same thing. One thing I try to consider is finding the least intrusive way possible to run this vent. You may want to discuss this with your plumber and have him explain his reasoning. If you don't care for his way of doing it seek another opinion. The imortant thing here is you need that vent and the work should be done in accordance with your local code. This work should be permitted and inspected.

    Properly installed you will have a good running system with no smells. Improperly installed you will refer to it as the "Stank Vat."
    Last edited by Redwood; 03-31-2008 at 10:03 AM.

  3. #3

    Default Vent location?

    Hi Redwood,

    Thanks for the reply. I'm totally onboard with having everything vented properly, and I definitely want to have a dedicated vent for the ejector pit. I just don't understand why my plumber says it has to be vented out the roof where it connects to the main drain, which is 30 feet from the pit (and would run right through the living room). Why can't we vent it straight up and out from the pit up through the roof (where the vent would run behind kitchen cabinets)?

  4. #4
    Master Plumber Redwood's Avatar
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    I would ask him his reasoning and that he explore other options or, get an opinion from another plumber... Personally I would probably try doing it closer if possible, but I am not on-site to see why. Kitchen cabinets could be a problem as access may be needed to the wall.

  5. #5

    Default

    I second Redwood's suggestion. If wall access to run a dedicated vent is available, there is no reason a dedicated vent would not work. As long as it is properly sized and connected, it will provide the necessary relief air to the ejector. It would also be used to vent all of the fixture drains.

    If there is no external concern such as demolition, it is possible that the plumber looking at the job hasn't dealt with an ejector before, and is just looking at the sample diagram in the installation manual (which likely shows the vent tying into the main vent up in the attic).

  6. #6

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    "He said that we would have to run a vent up out the roof from where the discharge line connects with the 4" main drain."

    That doesn't make sense to me.

    The only thing I can think of is that he's trying NOT to create a dedicated vent and second penetration thru the roof. Perhaps he intends to vent INTO the main discharge as a wet vent?
    (important note: I'm not a pro)

  7. #7
    Master Plumber Redwood's Avatar
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    For it to be a vent it would have to tie in above the flood rim of any of the fixtures served by that 4" vent. Wet venting between floors is a no-no.

  8. #8

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    Quote Originally Posted by Redwood View Post
    For it to be a vent it would have to tie in above the flood rim of any of the fixtures served by that 4" vent. Wet venting between floors is a no-no.
    It sounds from the original post like the original poster is trying to avoid tying to the main stack at all due to logistical concerns. (30' run across the corner of the living room)

    What nobody seems to be able to figure out is what his plumber was telling him. After re-reading the message, it sounds to me like the proposal is to tie the ejector's ejection port into the drain line (I presume it's horizontal, unless the ejector is being used to avoid busting concrete), and re-vent that connection. This would be superfluous in addition to the pit's own vent.

    I think the original poster needs to weigh in and clarify what he wants to do or avoid doing, and what his first bidding plumber wants to do or avoid doing.

  9. #9
    Master Plumber Redwood's Avatar
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    I would agree. He needs to understand what his plumber is wanting to do and why, then tell us. A 2nd opinion from another plumber would not hurt to investigate more venting options.

  10. #10

    Default

    Thanks guys. I got a second opinion, and the other plumber could not figure out why the first guy said the vent would have to run up where the discharge line hooked in with the main drain. This new guy wants to run a vent straight up from the pit and out the roof.

    One more question for you all. Does the vent for the ejector pit need to be a dedicated vent with nothing else tied into it? Or can we tie a sink and toilet into that same vent? The plumber is only talking about running one vent for the pit and fixtures right now. I just want to make sure that will be ok. Thanks.

  11. #11
    Moderator & Master Plumber hj's Avatar
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    Default vent

    I get the impression his plumber is under the misguided impression that the pump's discharge is a "fixture connection" and as such would need a vent. The only vents required for an ejector system are the tank itself and the various fixtures. The pump discharge can run hundreds of feet if that were required, and without a vent.

  12. #12

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    Thanks hj. So can we just run one large vent out the roof for the pit and also vent the toilet and sink with that same vent?

  13. #13
    Retired Defense Industry Engineer jadnashua's Avatar
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    If the vent is the proper size for all of the fixtures connected to it, one is fine. They need to be connected with slope in case they get moisture (rain, etc.) in them and high enough so a backup won't fill them up (nominally at least 42" above the floor), but other than that...there are few other rules.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  14. #14

    Default

    Is 4" the proper size vent for an ejector pit?

    And just for clarification... If the vent goes from the basement to the ceiling, then I can tie the vent from the toilet into the ejector pit vent down in the basement wall as long as the tie in happens at least 42" from the floor?

    Sorry for the all of the questions, but I want to do this right! Thanks again.

  15. #15
    Retired Defense Industry Engineer jadnashua's Avatar
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    I don't have the tables in hand, but 4" should be plenty big enough for a single bathroom. Probably bigger than needed, and harder to get up through the walls, but if you have room, probably no big deal.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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