Sanity check - clothes washer and laundry sink venting fix

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cliff_x

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Long time reader, was a big help with the kitchen I redid about a decade ago now, but haven't needed to ask a Q until now.


I'm having an issue with either the laundry sink or (more likely) the stand pipe for our clothes washer, we occasionally get sewer gas in the room, but I couldn't figure out the pattern/cause until the wall was opened up. It looks like it's the lack of correct venting on the standpipe (and that it's all 1.5" ABS.)

Originally the vertical pipe would have served only the kitchen sink and dishwasher on the floor above (and maybe a basement sink). This was changed at some point in the past, when the clothes washer and dryer were moved from the main floor to the basement. From reading a bunch of threads over the past couple of days (Thanks Terry for your picture on the ideal laundry setup,) to me looks like a couple of issues with the way it was done:

1) S-trap on the stand pipe
2) No vent on the stand pipe before it drops vertically
3) Undersized stand pipe & pipe below 1.5" instead of 2"
4) I'm not sure what buried AAV was doing with where it is installed, right idea in concept, but wrong execution?


This is the current situation for reference: (the sink cabinet goes over the floor cleanout, and the clothes washer is just to the right, but it's moved out of the way)
PXL_20230918_205735651.jpgPXL_20230918_172846987.jpgPXL_20230918_172713289.jpgPXL_20230920_022010361.jpgPXL_20230918_172759547.jpgPXL_20230918_172833443.jpg


Proposed solution: (any obvious mistakes, or things to look out for here - I'll be removing the existing AAV & standpipe along with their wye's)

PXL_20230921_010631535.jpgPXL_20230920_022651323.jpg


I'm in Mississauga, Ontario, Canada - which falls to Ontario as far as what I could find, the National plumbing code of Canada 2020 ed, was more detailed, so:


Looking at the section on wet venting (table 2.5.8.1) it talks about the total hydraulic load on the vent, and 2.5.8.1.2 says the most downstream fixture shall not be included.

Fixture units: (5 total)
Sink 1.5 (1st floor - dry vent)
Domestic dishwasher, no load when connected to domestic sink (1st floor - dry vent)
Clothes washer: 2 (shall not be included as it's the most downstream fixture)
Laundry tray 1.5


That leaves only the laundry tray at 1.5 units, which is less than 2 from the table, so I should be able to use the 1.5" vertical ABS to the first floor as a wet vent to eliminate the AAV, right?

Reading through Wet venting 2.5.2.1 - all of the other requirements are met. But have a question around 2.5.2.1.f - on what is meant by "the total hydraulic load does not exceed the limits from table 2.5.8.1" - am I counting all the fixtures without the exceptions: 1.5+2+1.5=5, or only after the exceptions - so just the laundry tray at 1.5? (I guess another way to ask, can I eliminate the AAV, by using a wet vent for the clothes washer branch?)
 

wwhitney

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Does the Canadian code you referenced really have no stipulation on wet venting that all the fixtures have to be on the same floor? All the US plumbing codes have that limitation. With a wet vent you wouldn't pull off a vent on the laundry standpipe trap arm, it would be vented by the san-tee.

On your drawing, if you eliminate the vent takeoff, and if the 1.5" line from the first floor were a dry vent, that would be the typical arrangement for a laundry sink dry vented and vertically wet venting a laundry standpipe. So given that you do have drainage from above, I'd suggest recreating that geometry along side the drain coming down, with an AAV instead of a dry vent (assuming you don't want to run the dry vent up to the floor above and tie into a dry vent there, above the flood rim of the first floor fixture).

Cheers, Wayne
 

WorthFlorida

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It does look like it is a venting issue, BTW, HE washing machines can have an mold problems that may mimic a sewer gas odor. Front loaders are especial vulnerable on the rubber gasket for the door. Top loaders not as bad but maybe on the outside tub or at the top rim of the wash basket. I have a used the tablets though I did not have any odors, just a maintenance item.

Google search "tablets to clean washing machine" and "how to sanitize the washing machine". There are plenty of pictures with mold grow from front loaders. Sometimes it can be cleaned or a replacement is needed.
 

cliff_x

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Does the Canadian code you referenced really have no stipulation on wet venting that all the fixtures have to be on the same floor? All the US plumbing codes have that limitation. With a wet vent you wouldn't pull off a vent on the laundry standpipe trap arm, it would be vented by the san-tee.

Here's the section from the NPC 2020 edition - there is a restriction, but my first floor is under the 4 fixture units. Ah, that makes sense that I wouldn't need to pull off a vent then.

Wet Venting
(See Note A-2.5.2.1.)
1) A sanitary drainage pipe is permitted to serve as a wet vent, provided
a) the hydraulic load is in accordance with Table 2.5.8.1.,
b) the number of wet-vented water closets does not exceed 2,
c) where 2 water closets are installed, they are connected at the same level by
means of a double sanitary T fitting if the vent pipe is vertical and by means
of a double Y fitting if the vent pipe is horizontal,
d) the water closets are installed downstream of all other fixtures,
e) trap arms and fixture drains connected to the wet vent do not exceed NPS 2,
except for connections from emergency floor drains in accordance with
Sentence 2.5.1.1.(3),
f) the total hydraulic load on the wet vent does not exceed the limits stated in
Table 2.5.8.1. when separately vented branches or fixture drains in the same
storey, having a total hydraulic load not greater than 2 fixture units, are
connected to the wet vent or a wet-vented water-closet trap arm,
g) the hydraulic load of separately vented fixtures that drain into the wet vent
are not included when sizing the continuous vent that serves the wet vent,
h) where a wet vent extends through more than one storey, the total discharge
from any one storey above the first storey does not exceed 4 fixture units,

i) there is not more than one nominally horizontal offset in the wet vent, and
i) the offset does not exceed 1.2 m for pipes of NPS 2 or less , or
ii) the offset does not exceed 2.5 m for pipes larger than NPS 2,
j) the nominal pipe size of the wet-vented portion is not reduced, except for
the portion that is upstream of emergency floor drains in accordance with
Sentence 2.5.1.1.(3), and
k) the length of the wet vent is not limited



On your drawing, if you eliminate the vent takeoff, and if the 1.5" line from the first floor were a dry vent, that would be the typical arrangement for a laundry sink dry vented and vertically wet venting a laundry standpipe. So given that you do have drainage from above, I'd suggest recreating that geometry along side the drain coming down, with an AAV instead of a dry vent (assuming you don't want to run the dry vent up to the floor above and tie into a dry vent there, above the flood rim of the first floor fixture).

Yea, the wet vent from above is the wrinkle for me. The ideal would be to connect up to the dry vent above, but with all the cabinets and backsplash, it's not really an option until the kitchen gets redone at some point in the future.

I've been going back and forth, but with your advice recreating the ideal, with the AAV instead of the dry vent should have less likelyhood of future issues than threading the code needle to use a wet vent. Thanks for the reply Wayne
 

cliff_x

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It does look like it is a venting issue, BTW, HE washing machines can have an mold problems that may mimic a sewer gas odor. Front loaders are especial vulnerable on the rubber gasket for the door. Top loaders not as bad but maybe on the outside tub or at the top rim of the wash basket. I have a used the tablets though I did not have any odors, just a maintenance item.

Google search "tablets to clean washing machine" and "how to sanitize the washing machine". There are plenty of pictures with mold grow from front loaders. Sometimes it can be cleaned or a replacement is needed.

Thanks for the reply, we run a cleaning cycle every once in a while - normally with oxiclean, replacing the door gasket is on my eventual to do list, as the machine is nearing 10 years old, and has a bit of mold that has embedded itself in the gasket at this point, but it doesn't smell - and that little filter is never has gunk in it when I open it up. We keep the door open when it's not in use which is supposed to help.


It's an intermittent thing, and I notice it more when I'm making beer and and I'm in the room for on and off over 6 hours (and both the kitchen & laundry sinks get used during that time) - it's not a wack you in the face level of it, but it is seems to increase over that time, and becomes a bit of an irritant to me.
 

John Gayewski

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Your plumbing does need redone. I'm also surprised that a vertical wet vent is allowed to extend between floor levels.

Since you can't open the wall in the second story and it's allowed I would go with your setup. The only thing I would do is try to run 2"pipe for the wet vent. I'm not sure if you can reach up high enough to change what you can now, but also make it so in the future, if the upper floor gets opened up, you could finish changing that vertical wet vent to 2"pipe all the way.

So I'd run 2"up as high as possible. Later if someone is redoing the upstairs they can reach down and cut the 2x1.5" reducer out and use a coupling to change it to all 2" pipe on that section.
 

wwhitney

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Here's the section from the NPC 2020 edition - there is a restriction, but my first floor is under the 4 fixture units.
But what about the wet vent sizing table--is the vertical drain carrying the kitchen sink from the floor above allowed to act as a wet vent while being only 1-1/2"? US codes would count the kitchen sink as 2 DFUs and require any wet vent carrying it to be at least 2" pipe.

Also, the unshielded rubber coupling in one of your picture is only listed for below ground use. When rebuilding, you should use only the shielded rubber couplings, a bit over 2" long, which are listed for above ground use.

Cheers, Wayne
 

cliff_x

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Your plumbing does need redone. I'm also surprised that a vertical wet vent is allowed to extend between floor levels.

Since you can't open the wall in the second story and it's allowed I would go with your setup. The only thing I would do is try to run 2"pipe for the wet vent. I'm not sure if you can reach up high enough to change what you can now, but also make it so in the future, if the upper floor gets opened up, you could finish changing that vertical wet vent to 2"pipe all the way.

So I'd run 2"up as high as possible. Later if someone is redoing the upstairs they can reach down and cut the 2x1.5" reducer out and use a coupling to change it to all 2" pipe on that section.
I'm also surprised - well, newly informed after reading the code over the past couple of days, but haven't needed to do any significant changes to my plumbing in quite a while. Changes to our electrical code is normally more restrictive than US codes, and it takes longer for ours to receive updates, so yea - doing a couple double/triple takes on it here, that it apparently allows me more lee-way.

Good idea, I'll change the drain pipe over to 2" and run it and the current AAV (the future vent line) up as high as possible, so a future retrofit will be easier. Thanks John!


But what about the wet vent sizing table--is the vertical drain carrying the kitchen sink from the floor above allowed to act as a wet vent while being only 1-1/2"? US codes would count the kitchen sink as 2 DFUs and require any wet vent carrying it to be at least 2" pipe.
I've read through a couple of times - the NPCC uses 1.5 units for the kitchen sink, and allows for 2 units with a 1.5" wet vent - so just under I think.


But the section - Vent Pipes for Stacks reads like it makes a bunch of the above moot, with section d) - it seems like it won't allow it, even with the wet vent section being more permissive.
2.5.4.2.4.d

d) all fixtures are located in the lowest storey served by the vent stack, and
e) the section of the vent pipe that acts as a wet vent conforms to the requirements regarding wet vents





Also, the unshielded rubber coupling in one of your picture is only listed for below ground use. When rebuilding, you should use only the shielded rubber couplings, a bit over 2" long, which are listed for above ground use.
Good catch, I'll make sure to rebuild it with a shielded coupling. Thanks Wayne!



Slightly updated version, with John's suggestion to update the stack to 2". I'd rather go a bit beyond code to make sure its reliable, than the minimum the difference in cost between the two isn't really all that significant compare to the time to redo it. Appreciate all the advice
PXL_20230921_154709355.jpg
 

Jeff H Young

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Id never wet vent between floors even if legal unless I ran it a couple pipe sizes over . so in your case id concider how your final drawing is except Id add either a vent or aav at the laundry sink.
 

John Gayewski

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Id never wet vent between floors even if legal unless I ran it a couple pipe sizes over . so in your case id concider how your final drawing is except Id add either a vent or aav at the laundry sink.
I never considered that option too. Maybe it's possible to slide a pipe from the bottom floor up to the attic.

My humble opinion adding an aav with a second story stack right directly next to it doesn't get you a lot, but running a seperate 1.5" pipe up through the studs onto the attic and out the roof could help. If that was possibe that would be great.
 

Jeff H Young

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I never considered that option too. Maybe it's possible to slide a pipe from the bottom floor up to the attic.

My humble opinion adding an aav with a second story stack right directly next to it doesn't get you a lot, but running a seperate 1.5" pipe up through the studs onto the attic and out the roof could help. If that was possibe that would be great.
Totaly agree, I was thinking dry wall damage but it might be a single story one hole in the basement another in the attic Tie in with K/S vent in attic kind of deal Ive put 2 or 3 drill bit extentions together to drill fire blocks in between .
My guess is wet venting between floors probebly gets done a whole lot more than Ive seen but you know how weve gone through this trade thats a Sin.
 

cliff_x

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My humble opinion adding an aav with a second story stack right directly next to it doesn't get you a lot, but running a seperate 1.5" pipe up through the studs onto the attic and out the roof could help. If that was possibe that would be great.
Not in the cards right now unfortunately - wish I would have discovered it when I opened up a bunch of kitchen walls to add & correct some wiring issues in prep for paint last year.

The kitchen sink is on an outside wall with cabinets, tile backsplash & insulation - so threading it up and cutting a hole isn't likely going to work, the other wall/ceiling that might have a vent for the bath on the second floor has popcorn ceiling - so it's opening a can of worms. My drywall repair is pretty good, but matching popcorn is out of my element. Once I'm in the attic, super easy to connect in to any of the venting though.
 

Jeff H Young

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why not put the aav on the laundry sink then and be legal? unless you are saying your p0lan allows wet venting between floors I only have opinion on UPC and IPC in the USA but we have bastard codes in a few areas or states. I personaly never heard of wet venting between floors though but not really going to check another country heck your country may have more than one jurisdiction as well anyway
 
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