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floor drain venting

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mikedo
mikedo Member Posts: 174
i live in ct we use the 2015 ipc. i thought they changed the length from the trap to where you can vent it. i can't find my 2015 book so I'm looking at the 2012 ipc. its not in there or i can't find it. if anyone knows the answer any help would be greatly appreciated. thanks mike

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  • mikedo
    mikedo Member Posts: 174
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    i found it in the 2012 ipc. 915.2 combination waste and vent i have the commentary book but i still can't interpret whats needed to do it.
  • plumbdummer
    plumbdummer Member Posts: 1
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    In NC you can roll a wye to a vertical position (or45) then arm to the nearest wall, however it must be “remote” which means not near another fixture.
  • hot_rod
    hot_rod Member Posts: 22,258
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    As I recall a combination waste and vent floor drain required a 3” trap then belled down to 2” at the drain

    So basically only a 2” volume of flow allowing air to vent across the flow In the trap arm and waste line. It still requires a VTR at some point

    The city required a stamped, engineered design

    This was a system for floor drains in a large brewery
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ChrisJ
    ChrisJ Member Posts: 15,784
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    Stupid question but what keeps all of those traps from drying out?

    I can't believe people can be trusted to dump water in them several times a year.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • MikeL_2
    MikeL_2 Member Posts: 494
    edited March 2020
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    Mikedo,
    I would check with your local building code official. Standard drain venting allows an 8' waste arm for 2" drain piping, a 12' waste arm for 3", and 16' for 4" - at 1/4" pitch; you may be able to extend the effective waste arm length using 1/8 " pitch per foot.
    We have installed trap primers on floor drains & basement grade showers to maintain trap seals......
  • hot_rod
    hot_rod Member Posts: 22,258
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    ChrisJ said:

    Stupid question but what keeps all of those traps from drying out?



    I can't believe people can be trusted to dump water in them several times a year.

    trap primers are one common solution

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Jamie Hall
    Jamie Hall Member Posts: 23,441
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    ChrisJ said:

    Stupid question but what keeps all of those traps from drying out?



    I can't believe people can be trusted to dump water in them several times a year.

    They don't (the people) and they do (the traps) and they (the people) complain about the smell...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • SlamDunk
    SlamDunk Member Posts: 1,591
    edited March 2020
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    The smell or sewer flies. Trap primers are great! But, if you dont have them, water topped off with vegetable oil to slow evaporation, is the next best thing.
  • Alan (California Radiant) Forbes
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    This is from the 2009 UPC:



    Sorry, I don't have anything more current.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • hot_rod
    hot_rod Member Posts: 22,258
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  • Alan (California Radiant) Forbes
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    I believe we're talking about two different things here.

    In the UPC code book, there are rules for residential and light commercial buildings.

    Chapter 9, Venting, has a section called Combination Waste and Vent Systems, that "shall be permitted only where structural conditions preclude the installation of conventional systems as otherwise prescribed by this code." You have to get approval from the AHJ before you can install this kind of system and it's probably for buildings like parking garages or markets where there are few walls for venting.

    As far as what @mikedo's conditions are, maybe he can shed some light.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • mikedo
    mikedo Member Posts: 174
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    they are floor drains in a bathroom farther than 8 ft from any wall. I'm thinking we can run 3 inch to the 2 trap and vent it at the nearest wall it is less than 25ft away. thanks for all the help.
  • Alan (California Radiant) Forbes
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    If you have plenty of room in the floor below, you can run the vent horizontally, with slope to the nearest wall.


    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • mikedo
    mikedo Member Posts: 174
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    thats what we did it failed inspection. a vent can not go horizontal.only on a 45 degree angle
  • hot_rod
    hot_rod Member Posts: 22,258
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    a horizontal vent needs to roll up above the centerline of the waste line, then you can run horizontal. Back in my day anyways :)

    So your need to start fairly deep in the sub-grade.

    The combination floor drain vent method works if you have numerous floor drains that will vent to a common vent.

    If you have one or two and a wall within 10 feet, you should be able to run a horizontal vent, with proper slope.

    Guess it comes down to what the inspector will pass. But you do want it to function properly.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    BillyO
  • MikeL_2
    MikeL_2 Member Posts: 494
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    Is someone able to provide the code language that allows dry horizontal venting below the flood level of a fixture or drain? I've never installed one, but changed scores......
  • BillyO
    BillyO Member Posts: 277
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    would you be referring to the way an island sink is vented?
  • hot_rod
    hot_rod Member Posts: 22,258
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    The link I posted up up a few with the ASPE link shows the code language

    There are various different codrs, not sure they all agree
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • BillyO
    BillyO Member Posts: 277
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    similar to shower, bathtub venting or toilet bowl venting.
  • mikedo
    mikedo Member Posts: 174
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    hot rod i think in that picture you posted they don't go horizontal until after there 6 inches above flood level thats why its legal. in the 2012 ipc 504.4 and 505.5 show a lot of diagrams in the commentary book. not very good on computer so i don't know how to post pictures. the combination vent system allows you to go farther until it must be vented by oversizing the pipe because it will never be full and air can move. thats how i an interpreting it but i not sure I'm right thats why i was asking for help
  • hot_rod
    hot_rod Member Posts: 22,258
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    This is how we typically vented a shower drain or floor drain, on either a framed floor or on a slab. It is a basic horizontal vent, not a combination. No other drains connect into that VTR "vent thru roof".

    If it was to be used with say a lav draining into that vertical vent then you have a wet vented fixture, different requirements. As I recall the vent fitting needs to be a Y not san t, the vent needs to be a size larger than the drain trap connected.

    The requirement on this assembly is the san tee needs to roll up so the vent take off is above the centerline of the drain. If not it was called a flat vent in my area and would not pass code. My picky inspector would get on a ladder to assure you had that tee rolled up properly, or fail it :)

    As far as I know that horizontal vent section can travels far as pipe size allows. With a 2" p trap in say a 10" joist, you start to run out of space to get adequate 1/4" per foot grade, even with the trap as low as you can get it in the joist depth.

    A combination drain vent for floor drains allows you to run longer distances as it uses an increased drain pipe size to allow the air flow over the water flow. In my area that needed to be drawn, sized, dimensioned, and stamped by a P.E. before we could install it. It still required a vent, as I recall one at both ends of the waste run. I'm not sure what the criteria is for sizing it, fixture units, pipe size, available air space when multiple traps are used, etc must be in the equation?

    Also a pic of how we would often wet vent a toilet with a 3X2 heel outlet ell, it saved individually venting the two fixtures.

    It's been 25 years since I was doing rough plumbing work, possible some of these requirements have changed. Or the way your local inspectors see them :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mikedo
    mikedo Member Posts: 174
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    the last drawing is illegal a vent cannot go horizontal below the 6 inches of the flood rim unless it is a wet vent. i used to do it just the same way you did but now the inspectors seem to be not allowing it anymore. it has to do with they don't want the vent to be able to be used as a drain. but if you go up after the horizontal run it can't be but they also don't want the vent to get plugged up. vents and venting the most important chapter in the plumbing code book. you can cut your rough work in half if you know the rules. thanks for helping
  • hot_rod
    hot_rod Member Posts: 22,258
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    So there needs to be a wall within 5 feet, or approved trap arm length, of any shower or floor drain? How else do you vent a trap in the floor?

    I'd ask them to show the section in the code. Maybe it has changed. Are you under the UPC code or ??
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • heathead
    heathead Member Posts: 234
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    What is a trap primer ?
  • hot_rod
    hot_rod Member Posts: 22,258
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    there is any number of different trap primer systems. basically squirt some water into the floor drain ocassionally.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • mikedo
    mikedo Member Posts: 174
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    sorry it was 905.4 ipc code.


  • hot_rod
    hot_rod Member Posts: 22,258
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    So be it. Doesn't leave a lot of options for large rooms with only exterior walls, and many floor drains.

    Not sure why you would need to vent a sink like that, must be a wall behind, or loop vent it? Are loop vents allowed still?

    So an engineered combination waste/ vent system is the only option for floor drains?

    Shower vents? All showers need to be within 5 feet of a wall?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MikeL_2
    MikeL_2 Member Posts: 494
    edited March 2020
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    Horizontal shower trap vents can be washed by a fixture drain, typically a lavatory which are usually 1.25 inches. This portion of the dwv system is called a combination waste & vent.
    Horizontal vents below a trap or fixture flood level can ( and will ) become blocked if there is a downstream drain blockage - the combination allows the vent access for rodding or snaking via the connected fixture drain.
    You can extend the length of a waste arm significantly by increasing the drain pipe diameter.....
  • hot_rod
    hot_rod Member Posts: 22,258
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    Interesting change.
    50 maybe 100 years worth of horizontal venting with what % of problems?
    How many of those horizontal shower vents have you seen get plugged, or had to snake?

    It seems the lav waste would present more potential to plug that horizontal section?

    I understand the intent, but it seems like a solution looking for a problem.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    rick in Alaska
  • MikeL_2
    MikeL_2 Member Posts: 494
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    Dry horizontal vents can be problematic, and in my 50 year career I've always found a way to avoid them. We've done scores of bathroom remodels and 100's of tub drain repairs / replacements. Most dry horizontal vents we find are at least partially blocked.....
  • hot_rod
    hot_rod Member Posts: 22,258
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    MikeL_2 said:

    Dry horizontal vents can be problematic, and in my 50 year career I've always found a way to avoid them. We've done scores of bathroom remodels and 100's of tub drain repairs / replacements. Most dry horizontal vents we find are at least partially blocked.....

    And in 50 years, how many have plugged to the point of not being operational-able?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MikeL_2
    MikeL_2 Member Posts: 494
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    Dozens. Keep in mind we're a 2 man shop so our contact is limited. I'm certain there are 10s of thousands of less than perfect dwv systems. I have discovered a handful of completely plugged vents ( most were horizontal ) that prevented toilets from flushing & caused constant gurgling, and some trap seal siphonage.
    I always prefer to choose an optimum install, the same way I choose a straight or plumb pipe vs crooked - if you have a choice, why install a crooked pipe? Dry horizontal venting has more potential for poor performance; most plumbing codes are based somewhat on potential......