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Thread: No vent for sink - any solution?

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    AMontemagni is offline Handyman
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    No vent for sink - any solution?

    My kitchen sink plumbing does not have a vertical vent and takes a minute or two to drain. There is no possible way of adding a vertical vent to this section of the house without significant renovation to the walls.

    Is there any other option other than a vertical stack to vent this so it will drain quicker?

    Thanks

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    LazyPup is offline Deity
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    We would need a bit more information to resolve your problem because a sink drain does not always require a vertical vent line running above it.

    Are your drain lines accessible from a basement or crawl space underneath?

    What is the diameter and length of the pipe from the vertical riser in the wall out to the P-trap under the sink & the diameter and length of the horizontal line under the floor from the vertical riser to the Stack or Horizontal line it connects to?

    Are you under the International Residential Code or the Uniform Plumbing Code as they both have some radically differing requirements for venting.

    If you can provide a bit more information I may be able to provide you an illustrated layout.
    Last edited by LazyPup; 05-02-2006 at 12:43 PM.

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    AMontemagni is offline Handyman
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    The drain lines are easily accessible from the basement.

    I have a S trap which is vertically down 14" below the garbage disposal. After the S-drap, it runs vertically down another 14" then swings 90 degrees into 1 1/2" PVC. After the 90 degree angle, there is the horizontal run into the vertical stack. That run is about 15'.

    I do not know what code I am under. I would like to stay within code, however, more so I want it to vent appropriately.

    Thanks in advance for your help.

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    From your description you have a number of serious code violations that are resulting in the problem you describe. Fortunately it will be very easy and fairly inexpensive to change it.

    With the singular exception of a standpipe such as a laundry standpipe, no vertical input to a trap may exceed 12" in lenght. (Yours is currently 14".)

    S-traps are prohibited.

    Under the International Residential Code "IRC", the maximum developed lenght of an 1-1/2" horizontal line from the trap weir (point where water spills out of a trap) to the vented stack or horizontal waste line may not exceed the diameter of the pipe divided by the required pitch. The required pitch for an 1-1/2" line is 1/4" per foot so the maximum lenght is 1.5" / .25" = 6ft.

    Under the Uniform Plumbing Code "UPC" that maximum length is derated to 3'6". (Currently your maximum developed length from the trap weir to the stack is in excess of 15'. This is the reason our line is not venting correctly.

    The codes require a cleanout at each change of direction greater than 45deg. Currently you have a 90deg bend with no cleanout.

    The Uniform Plumbing Code will allow a maximum of one (1) air inlet valve (commonly called a studor vent or cheater vent) per structure. Under the IRC once a structure has the required Main Vent you may use an unlimited number of AAV's.

    Before we begin discussing how to resolve your problem allow me to explain how PVC fittings are identified.

    PVC piping may be used for both water supply piping and DWV (Drain, Waste & Vent) applications however pressure and DWV fittings are not interchangable.

    All PVC pressure fittings have sharp bends where they change direction and they are identified by the angle of the bend. I.E. 90deg elbow, 60deg elbow, 45 deg elbow, etc. (These may not be used on a drain line.)

    All PVC DWV fittings will have a slight radius in the direction of flow or as in the case of a WYE fitting the pipe enters at an angle directing the flow. In order to help identify DWV fittings versus pressure fittings, DWV fittings are identified by a "Fraction of a circle" thus a 90 deg elbow for DWV piping would properly be called a "1/4 bend" (360deg / 4 = 90deg thus a 1/4 bend)

    Most pipe fittings have a female hub on each end to accept a pipe input, but some fittings have a female hub on one end and "male spigot end" on the other end. This permits connecting one fitting directly into another without the need of a section of pipe between them.

    Now let us start on your project:

    Begin by cutting the 1-1/2" horizontal pipe below the floor and remove the 90deg elbow, veritical riser and S-trap and tailpiece up to the disposal.

    You will need more horizontal clearance at the disposal to install a P-trap so I would suggest you begin by attaching the P-trap to the disposal outlet and the new trap adapter on the P-trap. You will then be able to measure the required horizontal clearance to determine where your new vertical riser from below will need to be.

    Drill a new hole through the floor for the new riser.

    Now go in the basement and extend the existing 1-1/2" horizontal line to a point where you can attach an 1-1/2" Wye with the side inlet on top of the pipe. The inlet will be at a 45deg angle to the pipe so you will now install a Street 1/8th bend (45 deg) into the Wye side opening and adjust the 1/8th bend to give you a vertical opening under your hole. Install a section of 1-1/2" pipe to make a new riser up into the cabinet. On the open end of the wye you will install a Cleanout thread adapter and a cleanout cap to close the line. You may use a "Combo" in place of the Wye & 1/8th bend. A combo is a Wye & 1/8th bend made in one fitting to simplyfy the job but either method is equally acceptable. Care though, code prohibits installing a "Sanitary tee" on a horizontal line.

    When you have the section below the floor completed you may need to install additional hangers to support the pipe. You may use either the preformed PVC J-hooks or you may use vinyl perf strapping but you may not use any wire or metal hangers to support plastic pipe.

    Moving up to the sink now, measure the height were a "Sanitary TEE" will fit with the side opening pointing towards the trap. (You may not use a Wye &18th bend or combo on a vertical riser).

    You may attach the trap adapter directly into the side inlet of the Sanitary Tee or you may extend the horizontal line over towards the P-trap as needed, providing you do not exceed 3'6" horizontal from the tee to the trap. (The IRC would allow 6 ft but at 3'6" you will be good for whichever code is in your area.)

    From the top of the Tee extend the line a minimum of 4" vertical and install a cleanout thread adapter on the top of the pipe. You can then screw a studor vent into the threaded adapter to provide your vent and since it is easily removable it meets the requirement for a cleanout also.




    NOTE: I prepared an illustration but the program will not let me upload it. Send an email to LazyPup@yahoo.com and i will reply the illustration. In the mean time I will contact Troy and see if we can get the illustration posted here.
    Last edited by LazyPup; 05-03-2006 at 03:34 AM.

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    AMontemagni is offline Handyman
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    I can obviously tell you are a plumber ... and hope you used a program to put that diagram together because it looks like you spent a lot of time on this.

    I do understand the diagram perfectly, though.

    Couple of additional quesitons...

    Would the AAV let ANY gas out (or is it designed not to do so)?

    I see you put a minimum height of 4" for the AAV above the P-Trap, what is the maximum height?

    Is it acceptable to use an AAV for other than a sink (tub, toilet)?

    Forgetting about the code for a second, wouldn't it be easier to install the AAV attached to my existing S-Trap? Wouldn't that work just as well?

    Thanks

  6. #6
    LazyPup's Avatar
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    Thank you for the kind words about the illustration.

    About two years ago Hayzee produced some very nice electrical prints using the Microsoft Paint Program which comes pre-installed on most computers. Following his lead, i then began trying my hand at it. It did not take me long to learn some of the neat tricks you can do with that program and in fact it took less time to produce that illustration from a blank screen than it did to post the text answer. If you get a chance scan through the illustration library or some of the other posts and you will see numerous illustrations, all of which were done from scratch with the M.S. Paint program.

    Now to answer your questions:

    Air Inlet Valves have an internal spring loaded diaphram that will permit air to enter the pipe but it will not permit air or sewer gasses to come out.

    Under the Uniform Plumbing code they only permit a maximum of one AAV per structure and then only with the approval of your inspector. In most circumstances they only permit it for venting a sink in a kitchen island where you cannot run a vertical vent, and even then they prefer to see an "Island Vent" loop. The International Residential Code requires all structures to have a Main vent which runs undiminished in size from the house main drain through the roof. After that you may use any number of AAV's to create auxillary vents when required.

    The minimum height for the AAV is 4" above the line it serves. Their is no maximum and in fact you can run the line through the roof if you prefer, then you wouldn't need an AAV.

    An AAV must be installed in an accessible location that is open to air so that it can be serviced or replaced if the diaphram should get stuck. (They may not be installed inside a wall.)

    Now in regards to connecting the AAV to your S-trap.

    In the first place, S-traps are now code prohibited so it would not be prudent for me to tell you how to install one.

    You could probably figure out a way to jury rig it in but whether you mickey mouse that or do the job as I specified you will still need to buy some fittings. In truth the fittings are very cheap. I would estimate the AAV will cost about $5 and all the pipe and fittings I specified to convert to full code compliance will only be about another $20.

    You will also need some Glue and primer that is rated for PVC pipe. when selecting primer you will find a clear primer and a purple primer. Either one will work equally well. The only difference being the addition of the purple dye in the purple primer. In new construction or any job that will require an inspection we use the primer with the Purple dye so the inspector can be assured that we use primer before glueing.

    You will see a nice scissor type PVC hand cutter in the stores. Those are handy when you have a lot of pipe to run but you don't need it. You can easily cut PVC pipe with a hacksaw or a common wood type handsaw. In fact, in a tight spot you can actually cut PVC pipe rather easily with a piece of Nylon String such as used by masons for grade strings.

    After you cut the pipe you should use a pocket knife or utility knife to scrape the edges of the cuts to remove all the sawdust like burrs before you install the pipe.

    To answer one of your other questions ,,i am a certified Master Plumber.

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