Counter Windows & Waste Plumbing - Cross Post w/ Kitchen Forum

toddimtJune 7, 2011

Typically waste lines need to have the vent placed higher then the flood level of the sink. In the case of counter height windows or when the counter extends into the window, the vent line will have to go horizontal under the counter /window height and thus below the flood level of the sink.

Curious as to how the venting of the sink drain was handled for those with counter windows. Not sure if one uses the same type of high loop vent that is typical of island sinks or if the horizontal run of the vent under the counter level is ok for the 3'- 4' until you can go vertical past windows/framing.

Not sure if anyone has pics of the plumbing during construction.

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Under no circumstances may a vent be run horizontally at an elevation which is less that 6" above the flood level rim of the highest fixture served by that vent.

An Island loop vent may only be used in an island or a situation where a vertical vent cannot be achieved, and in all cases the use of the island loop vent requires specific approval of the local AHJ.

Having said all of that, I am still puzzled as to why you cannot achieve a standard vent?

If you are under the UPC a kitchen sink requires a 2" diameter fixture arm and a 2" diameter fixture arm may run up to 5' from the trap weir to the vent opening. Assuming one foot from the center sink to the wall you would still have about 4' which you could run horizontal to the side of the window and run the vertical drain & vent up through the next stud cavity on the side of the window.

Under the IRC the fixture arm only needs to be 1-1/2" but the IRC allows an 1-1/2" fixture arm to run up to 6' so you would have even more length to work with.

Actually if you were to begin by running the fixture arm at an angle from the trap to the side you could even gain a bit more length.

With careful planning and figuring in the length of the trap from the drain to the trap wier you could run a conventional waste arm to vent run with the sink centered in front of an 8' window and I doubt your window is even that wide.

Taking this to the limit, once the fixture arm is attached to the vertical drain the vent from the top of the sanitary tee could be further offset with a vertical 45deg offset which would give you another foot or so.

Keep in mind that a line that has an offset that rises at 45degress or more is still said to be a vertical line.

    Bookmark   June 8, 2011 at 1:39AM
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todds, "Trap Arm" may be the notion you may need to work with.

A longer "Trap Arm" lets peninsula sinks be properly connected to vertical vents that are in the closest wall.

The window/counter setup you described is the same as whatever DWV plumbing setup happens for sinks in peninsulas of all shapes. No window needed.

In other words, go pick up vertical venting over where there is no window.

a.f.a.i.k. a house must have lots of real venting and almost no Studor/AAV venting. This is serious, in houses where there are toilets on a second floor above the main floor. It is less serious in a single-level house because there is no drain plumbing above the main floor ((i.e. on a second floor). Studor/AAV vents transfer air only one way, so they handle only "positive pressure". Real vents allow air to move both ways; this is required in most arms of the DWV plumbing branching tree.

How to handle effluent is a serious concern, so don't let internet strangers advise you on cutting corners. Only someone on site can see the geometry you have in your DWV plumbing in your house. DWV plumbing requires a lot of 3D thinking. Words written are almost never good enough to describe everything, unless the person writing is a Master Plumber and the person reading it has the same level of knowledge allowing him/her to interpret the precise words, and they happen to agree on what they mean. This can happen in forums inhabited by Master Plumbers. But even there, it requires a few posts for them to go back and forth to be sure about what they mean. For many years, I have been participating in forums inhabited by Master Plumbers (under another handle/name).

If you posted diagrams that showed critical distances very clearly, you could receive some comments that help you see more clearly what options you might have, in your case.

When a DWV plumbing system is not well designed, it allows e.coli, salmonella, dangerous gases, and fecal matter waste contamination to spread beyond the area that should have contained it. In DWV plumbing an exchange of air for water happens every time you flush. The Studor\AAV thingie is an imperfect thingie that will one day fail (years from now); when it fails risk and danger are increased by several orders of magnitude. Before it fails, it is unable to handle air moving both into and out of it : it only lets air in, when negative pressure pulls air into it.

Just remember that the answer to the question about Studor\AAV vents is always "maybe" until your entire house plumbing is known to the answering party.


    Bookmark   June 8, 2011 at 7:41AM
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AAV block under positive pressure. (I wrote "they handle it").
AAV let air in when negative air pressure opens them.

No matter how well I describe it, my words are not enough to meet the technical precision that occurs when two trained professionals interact using the terms of their field.

    Bookmark   June 8, 2011 at 8:11AM
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Spoke with the local AHJ this morning.

Totally not for using any air admittance valves. I didn't bring it up, was just asking him what options I may have. Davidro1, he basically stated all the reasons you mentioned.

Told me with a disposal and DW on the line, he would want the "Trap Arm" to be 2". He mention venting w/ 2" pipe and I wondered why since the only fixture on the line was the sink/dw/disposal. Told me the 2" line should be vented w/ 2" . The one book I had showed a 1.5" vent would serve 8 fixture units (This kitchen sink is 2) and could run for 60' which is WAY more than enough. Trying to limit the hole needed through the top plate. When I mentioned using 1.5" he told me that it should be 2" but he would let me use 1.5".

I then can run the 2" trap arm up to 5'. I have 2x4 walls so in order to run this 2" pipe in the wall, I will need to drill out a nice chunk of the cripple studs, under the window, as well as the last cripple, jack & king stud to get to the free bay to run vertical for the vent and the vent to attic & drain to the basement. I would use the Simpson Heavy Duty Strong-tie Stud Shoes for the studs since they will be over bore'd.

    Bookmark   June 8, 2011 at 9:39PM
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