Adding Vent to Laundry Standpipe

[qlopp]

Hi,

I have a restricted trap below my laundry standpipe that can no longer handle the spin cycle output of my washing machine. It is the original installation from 1962; a 2" cast iron pipe goes below the concrete floor to a buried trap. Several times over the last 15 years I was able to snake it out with a 3/8" power drum snake and small "cutter" (I took a beehive attachment and cut off all but a little spur of the wire so that it would be slinky enough to make it through the trap). I can't snake it anymore due to corrosion bloom inside the trap.

This standpipe is just a stub and is not vented externally. It is located in a corner of the basement, 9" from the gable end wall of the house and 36" from the front wall of the house. It is one foot horizontally from a hopper window on the gable wall.

I've done research on what the correct repair would involve, which is to bring it up to code by cutting out the old trap and retrofitting an above floor trap. Then the drain must be vented to the exterior. It is here where I am unsure about all of the plumbing code stipulations. Paraphrasing from several sources, the vent terminal must be 10+ feet above outdoor ground level, then it must be 10+ feet horizontally from an openable window/door or intake/exhaust port unless it is 3+ feet above such opening(s). Unfortunately there is a basement hopper window very close to the drain location and one window each on the first and second floors above that window. By the time I navigated around these restrictions I would be at the attic level. Therefore roof exit seems like the only choice.

I am in an unincorporated county area which has adapted IPC. We have the least layers of government oversight in the populated areas of the greater metro area. Is there any chance of being granted a variance for retrofitting such a code compliance upgrade in a simpler manner than going all the way through the roof? Maybe a wall exit compromise that inspectors would allow in this situation, given the difficulty of achieving full compliance? It's not a conventional soil stack (so no human or food waste) and the trap breaks vapors from the lateral it connects to, so I don't consider that unreasonable.

If I hire a company to do this, how involved is running a pipe inside the exterior wall, up two stories and through the roof of a stick frame house, including flashing/roofing restoration and patching/restoring the appearance of any access holes in the walls? It seems like an expensive proposition, but maybe it's not as bad as I'm thinking.

Thanks for reading!

 

[MicEd69]

Your easiest solution is to use an AAV for your vent. If your county hasn't added any restrictions to IPC, they are allowed.

And realize, just because there are no household wastes flowing through your standpipe, the vent pipe from that P-trap will have an air path from your house's sewer gases.

 

[qlopp]

Your easiest solution is to use an AAV for your vent. If your county hasn't added any restrictions to IPC, they are allowed.

And realize, just because there are no household wastes flowing through your standpipe, the vent pipe from that P-trap will have an air path from your house's sewer gases.

View attachment 43176

Thanks for your reply. AAVs are often forbidden but I could ask. I wouldn't mind for this particular situation as unvented standpipe use has never presented an issue for me in the decades of laundry I've done.

But considering the unique situation of laundry discharge, it is far and away the greatest volume over time of water of any home fixture. That creates positive pressure on the vent IF there were to be a blockage downstream. The vent's secondary purpose is to allow gasses/pressure to escape. An AAV can only allow air into the drain for drafting purpose.

 

[MicEd69]

But considering the unique situation of laundry discharge, it is far and away the greatest volume over time of water of any home fixture. That creates positive pressure on the vent IF there were to be a blockage downstream. The vent's secondary purpose is to allow gasses/pressure to escape. An AAV can only allow air into the drain for drafting purpose.

You are correct in all that. However, if there is a blockage downstream, the standpipe will overflow due to the blockage in the case of an AAV OR a vent to the atmosphere.

I do not like AAVs in any cases, but this could be the exception.

And as I stated, your statement of "the trap breaks vapors from the lateral it connects to" is incorrect. Vent lines are connected downstream of the P-trap thry are serving, so there will be sewer gases coming out of that vent pipe. As such, getting a variance to allow a sewer vent to discharge any place other than a code compliance location is pretty doubtful, IMHO.

 

[qlopp]

You are correct in all that. However, if there is a blockage downstream, the standpipe will overflow due to the blockage in the case of an AAV OR a vent to the atmosphere.

I do not like AAVs in any cases, but this could be the exception.

And as I stated, your statement of "the trap breaks vapors from the lateral it connects to" is incorrect. Vent lines are connected downstream of the P-trap thry are serving, so there will be sewer gases coming out of that vent pipe. As such, getting a variance to allow a sewer vent to discharge any place other than a code compliance location is pretty doubtful, IMHO.

Thanks for the discussion. I had tried to post a reply but it isn't showing up now. Long story short, there must have been a miscommunication somewhere; I understand that gasses would travel out of a standpipe vent (if one existed). I was referring to gasses being trapped at the standpipe trap if it wasn't vented (like with my current situation). I was mentioning this because a non-vented standpipe has never presented a bothersome situation in my decades of experience of doing laundry. I can sometimes smell slight odor from the laundry discharge which ranges from not great (first discharge of dirty/soapy water) to perfumed (second spin after rinse). I have never smelled sewer gas because the trap never gets a chance to dry out.

 

[MicEd69]

I was referring to gasses being trapped at the standpipe trap if it wasn't vented (like with my current situation).

Yes, the gases that are trapped by your current standpipe are sewer gases with a smell. Anything you smell on the standpipe side of the trap is from you washing machine.

 

[qlopp]

Hi,

I have a restricted trap below my laundry standpipe that can no longer handle the spin cycle output of my washing machine. It is the original installation from 1962; a 2" cast iron pipe goes below the concrete floor to a buried trap. Several times over the last 15 years I was able to snake it out with a 3/8" power drum snake and small "cutter" (I took a beehive attachment and cut off all but a little spur of the wire so that it would be slinky enough to make it through the trap). I can't snake it anymore due to corrosion bloom inside the trap.

This standpipe is just a stub and is not vented externally. It is located in a corner of the basement, 9" from the gable end wall of the house and 36" from the front wall of the house. It is one foot horizontally from a hopper window on the gable wall.

I've done research on what the correct repair would involve, which is to bring it up to code by cutting out the old trap and retrofitting an above floor trap. Then the drain must be vented to the exterior. It is here where I am unsure about all of the plumbing code stipulations. Paraphrasing from several sources, the vent terminal must be 10+ feet above outdoor ground level, then it must be 10+ feet horizontally from an openable window/door or intake/exhaust port unless it is 3+ feet above such opening(s). Unfortunately there is a basement hopper window very close to the drain location and one window each on the first and second floors above that window. By the time I navigated around these restrictions I would be at the attic level. Therefore roof exit seems like the only choice.

I am in an unincorporated county area which has adapted IPC. We have the least layers of government oversight in the populated areas of the greater metro area. Is there any chance of being granted a variance for retrofitting such a code compliance upgrade in a simpler manner than going all the way through the roof? Maybe a wall exit compromise that inspectors would allow in this situation, given the difficulty of achieving full compliance? It's not a conventional soil stack (so no human or food waste) and the trap breaks vapors from the lateral it connects to, so I don't consider that unreasonable.

If I hire a company to do this, how involved is running a pipe inside the exterior wall, up two stories and through the roof of a stick frame house, including flashing/roofing restoration and patching/restoring the appearance of any access holes in the walls? It seems like an expensive proposition, but maybe it's not as bad as I'm thinking.

Thanks for reading!

Hi,

To sum this up I found out the subgrade trap had rotted through at the bottom which caused the snake to get stuck rather than going through the trap. I ended up repairing the stand pipe and added a tall section of vent and Studor AAV. This will be converted to a through-the-roof pipe at a later date if/when a renovation or citation requires it. It works great. I also cleaned up a free but nicer/newer washing machine than what I had been using and put it in service after the repairs.

 

[Twowaxhack]

That’s what they do. Very typical.