Hi, This is such a fantastic forum for the do-it-yourselfer... I really appreciate that you are all so generous with your time and expertise!

My wife has severe arthritis and I am relocating the laundry from the cellar of our 50-foot ranch home. I have scoured this forum and it has left me with more questions than just with my job at hand... I'm not sure the limit WRT attachment size but my first general issue with the house (modular home built in 1986) is that there is a vent close to the septic tank (and no outside / ground vent) drain and near existing laundry and my research here makes me question the design. The vent runs from the point in the picture directly out the roof with no other connections. Is this a problem in general? This downstairs laundry would also back up with suds occasionally and I think that would make sense considering the placement of the vent WRT to the drain/septic. Both tub/showers have p-traps below the floor (in cellar) and are unvented. The stack ends at the middle of the house and my laundry would be ~17 feet downstream. No permit & I was planning to use a washer box on an inside wall with 2-inch standpipe and ideally locate the 2-inch p-trap similar to others in design (below the floor) and could add an AAV (in cellar near p-trap), if this is OK for this system. Do I have more problems than a too-long honey-do list?

Thanks in advance for your help!

Here is the picture I referenced (sorry):

http://www.flickr.com/photos/54981851@N06/5093448607/

Hi,

If understood correctly that they have a vent to vent the entire house. It sounds like a wet vent which would be roughed in, in which it was the last resort because conventional venting was impossible. This venting is more applicable when no walls are present to vent fixures and has to be approved by the administrative authority. This type of venting must break @ 45 degree minimum of the drain line.

Anyway, make sure that the new washer to be roughed in is vented properly. And most importantly, washer box P-TRAP must be above floor and maintain a 2" standpipe and trap drain. I tried to picture your explanation and if wrong I apologize. GOODLUCK

Thank you,

I think you picture it well. With the existing venting approach, would an AAV be an option - I don't want to create a problem by introducing an AAV, but this is in a finished room (modular house... same headaches WRT venting through walls, attic, roof... only amplified) and adding a vent to roof is not an attractive option. What is the down-side (beside not being to code... ) to locating the p-trap immediately below the floor? Should this work? Seems like having the trap buried in the wall would not be highly desirable either...

Don't get me wrong it is your house and you do whatever u want. Lets say if u try to sell your house one day, they probably require a home inspector ask to bring to code. With improper venting , you would have drain issues because you need air to push and pull the liquid waste on its way to public or private sewage system. Think of it plugging one end of the straw w/ liquid in it, it stays in the straw.

Thanks. I guess these are my specific questions:

1. Will the AAV work?

2. In the situation I have with the single vent, will it (AAV) cause me any issues (for example, am I opening my interior to noxious gas by installing this or do I run the risk of that happening if it fails... then I have to open up a finished wall to replace it, etc. - is this only the case if the AAV fails, etc.)? Could the AAV be under the floor? How far from the p-trap can it be located (to be effective)? I'm in MA, I don't think the AAV will be to code - only because I haven't seen them used but I will check...

3. Am I already in the sale/inspection situation you describe WRT the other 2 p-traps being below the floor or I they OK since they are for tub/showers - just also seems like burying the trap in the wall could be an issue... if not, that's what I'll do... it will require a dog-leg or couple of 45s, etc... Will I experience an inspection issue in general WRT the single-system vent? I thought code had each drain requiring a vent tied in within so many feet... will I just feel good about my new work and fail due to the other drains that don't have local vents?

Thanks for your help.

What is AAV and WRT about? I apologize, just got home from a busy day. THANKS and I'll be waiting

Sorry, AAVs, or Air Admittance Valves, are mechanical devices used to equalize drain pressure in place of vent piping in many applications:

http://www.toolbase.org/Technology-Inventory/Plumbing/air-admittance-valves

When they fail (they are essentially a check-valve), they will let noxious gas back-flow (probably why they aren't to code in many locations... ) - that was one reason why I was wondering if a drain system would operate & be robust with the p-trap directly below the floor... because if I could locate this valve in the cellar it would not be as much of an issue if it failed (it would be readily detectable & accessible in that case, etc. versus being inside the wall if I located the p-trap above the floor, as I understand should be correctly done to meet universal code... ) and this valve would allow me to avoid venting through the rough since there is no vent near the installation.

WRT is just my lazy shorthand for "with respect to" :-)

Hi again,

O.k. thanks for the name AAV. In my location they call it studer vent which works the same way. This vent with my experience I install primarily for example, a B.B.Q. backyard sink because there is no walls adjacent to it so it would be under the sink. By the way, I have not heard of it failing.
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As far as your venting comments I can see why the washer would have sudsing issues. Because of improper venting, you do not have equal atmospheric pressure on the inlet side of fixture and the outlet of your trap when its discharging. It creates turbulence in your drain and sudsing becomes compressed and will find least path of resistance which is your basement.

As far as codes, fixtures are to have its own vent, or be wet vented. Basically how it works is your cross sectional area of your building sewer should equal the cross sectional of your vent. If your sewer is 4" then your vent should be 4" as well. Or run vents that equal the 4". Your vent is limited to a length w/ each pipe size.

Your AAV shouldnt be below floor because if u have a backed up sewer it be wet. With a 2" trap or trap arm, it should be 5' away from where it enters the sanitary tee according to UPC AND CPC CODES. Your state codes varies. Goodluck. Any questions please keep in contact.






Hi,

Yes it is called studer vent in my area. I have not heard of it failing. AAV shouldn't be underfloor because if it backs up it be wet. And yes each fixture must be vented on its own or wet vented. Also each pipe for venting and drain purposes has length limitations vertically and horizontally. AAV would be installed mainly when a fixture is not near a wall for instance, B.B.Q sink in the backyard.

2" trap arm distance in my area is 5' from trap to sanitary tee where it discharges into.

Lastly, your washer discharging suds because it is improperly vented in which creates turbulence and suds becomes compressed and escapes to least path of resistance. Basically your vent should have the same cross sectional area as your building sewer. Example, if your building sewer is 4" trap arm distance in my area is 5' from trap to sanitary tee where it discharges into.

Lastly, your washer discharging suds because it is improperly vented in which creates turbulence and suds becomes compressed and escapes to least path of resistance. Basically your vent should have the same cross sectional area as your building sewer. Example, if your building sewer is 4" as well. Or have multiple vents that equal the area of sewer.

Any questions keep in contact. THANKS