Vent?

[swolsen]

Can anyone tell me what this is used for? To me it looks like a vent that would allow makeup combustion air for the furnace and water heater. Not sure. I did not notice where it came in on the inside but it caught my attention as I came across it from the outside. [:-magnify

http://tijonline.com/forum/uploads/swol ... Pic069.jpg

[hausdok]

Is that a chimney? Could it be an air inlet for a fireplace?

OT - OF!!!

M.

[Brandon Chew]

Hi Scott. It looks like the termination of the vent for the main building drain to me. In the basement, right near there, should be where the main building drain is exiting the house. There is probably a trap in that line and what you are looking at is where the vent for the trap exits the house.

The net free area of that vent looks much too small for it to be for furnace & water heater combustion air.

Brandon

[swolsen]

Hello Mike,

No that is not the chimney. Just brick veneer from the front west side of the home. The fireplace utilizes a metal flue up through the roof in the middle between the house and an addition and has a chase where it extends from the roofline.

Brandon, I think you may have it. That is near where the sewer line exits the building. Thanks for the response. I have seen these before but never thought to ask until now.

Thanks Brandon.

[hausdok]

Must be a regional thing. I've never seen one of those before.

OT - OF!!!

M.

[Chad Fabry]

If Brandon's right then that's not a good area for a picnic table.

I've never seen one either.

I agree that the net free area is too small to be an adequate combustion air inlet.

[Steven Hockstein]

I agree that it is a sewer vent. It is regional.

In some towns around here it was required as part of the local plumbing code to provide a through-wall vent and a whole house trap for the sanitary sewer. I see this mostly on houses built between 1945 and 1960.

Is it common in your area to leave the foundation blocks bare?

[Neal Lewis]

We see these frequently in NJ for older construction. The house trap cleanouts are usually recessed or flush to the basement floor, and they are convenient to broom the water seepage into. I've seen the through wall vents completely removed with no effect on drainage. A regular stack through the roof was also installed during original construction, so the vent seems redundant.

[swolsen]

This particular home was built in 1990. Here is the trap that Brandon was referring to, pointed to by the red arrow. The blue arrow points to the pipe that extends to the outside vent in my original post.

http://tijonline.com/forum/uploads/swol ... Pic033.jpg

This is a house that was built in 1993 in a nearby development. It too has the same type of trap with the vent pipe extending through the wall's band joist in the front of the building.

http://tijonline.com/forum/uploads/swol ... 529_p1.jpg

http://tijonline.com/forum/uploads/swol ... 347_p2.jpg

http://tijonline.com/forum/uploads/swol ... 528_p3.jpg

I learn something new every day.

[Chad Fabry]

We're required to extend the vent through the roof. Don't folks get bothered by essence of sewage ?

[swolsen]

Hi Chad,

For both of these homes, at the time, I did not detect any sewage gasses emanating from either vent. I am wondering if it has to do with the whole house trap. I am sure there must be some venting at one time or another, maybe as fixtures are being used.[:-sour]

I did neglect to mention that both of these houses do have vent stacks through the roof in addition to these side wall vents.

[Chad Fabry]

If they have roof stacks, what the heck are the wall vents for?

[swolsen]

I just got back from the building department for Colonie, NY where these houses are. The Residential Builing Inspector handed me a sheet with this very reqirement on it.

http://tijonline.com/forum/uploads/swol ... DWV001.pdf

He did say that this is still in practice today. I told him of my concern with regard to sewer gases venting into windows above these types of vents and asked him what the purpose of this vent was for. He did not seem to know and directed me to the sewer department. I spoke to the head sewer engineer at the sewer department and he told me that the sewer department's juridiction stops just before the home and reiterated the fact that it was a vent but could not elaborate on why it is installed in the wall.

From the diagram it looks as if it is a fresh air inlet and not an outlet. I would fathom that the through the roof vents need a source to draw the air from in order to vent the interiors plumbing since it can no longer get that draw from the street sewer having the house trap installed.

[fqp25]

Swolsen,

That is strange. Is this a requirement for new construction, or just for whole house traps?

[swolsen]

Hi Frank,

According to the Residential Building Inspector this (the trap and vent) is required on all new residential construction. I did not get into specifics as to when they started doing this but the two houses I came across are from the early 1990's. Not sure how far back it goes. I am not sure where they get this code from but I intend to talk to the plumbing inspector in my town to see if he can shed some light on it.

[Tom Corrigan]

Scott,

This standard NYS code stuff. Come to the next ASHI meeting and I'll explain it.

Tom Corrigan 518-281-7007

[Steven Hockstein]

One of my clients recently failed his plumbing inspection because he installed a whole house trap. The plumbing inspector required it to be removed. The builder usually works in NY and was confused by the differences in requirements.

[fqp25]

Is that a state wide code, or just regional?

I have always been under the impression that it's kind of a standard to remove them. Never seen any Code about it though.

What other antique plumbing do they require there? Do they require builders to install drum traps as well???

[Bill Kibbel]

Having seen hundreds of these vents, and originally thinking they're a dumb idea, I'll add what I have learned about them over the years.

They're called "relieving vents" or "fresh air vents" for the "building trap".

For the past several decades, building traps generally have not been permitted to be installed except some municipalities still allow them where local conditions "necessitate such traps". I don't know where or what those conditions are. Through-the-wall vent terminals are not permitted except for the vent for the building trap, where provided.

[homnspector]

"We're required to extend the vent through the roof. Don't folks get bothered by essence of sewage ?"

According to Hillary, there is no essence of sewage in NY.

O.S.D.S.

[Brandon Chew]

The building trap and vent is in the old NYS Code Manual with a note next to a schematic that says "provide building trap and fresh air inlet as above when required by building official". It is carried forward into the NY version of the IRC (currently based on the 2000 edition), with a change in the wording which now reads "Building (house) traps shall be prohibited, except where local conditions necessitate such traps as required by the code enforcement official." So, in NY, the decision is left to the individual AHJ and you will find them in some municipalities and not in others. The building trap/vent is completely separate from the regular plumbing vents that go through the roof and which are still required.

The purpose and function of the building trap and vent is similar to the individual fixture trap and vent, except it is for the entire house. The building trap creates a water seal so that gases from the outside sewer line do not flow back into the house drain plumbing, and the vent is there to ensure the building trap functions properly. One difference between the building trap vent and the fixture vents is that the building trap vent is connected on the inlet side of the trap.

Like Bill, I haven't been able to figure out yet what specific conditions warrant the use of the building trap in one jurisdiction and not in another. I suspect that the guy who made the original determination that they are needed for his municipality is either dead now or long retired.

Without the building trap, gases from the sewer enter the house plumbing and are vented from the rooftop vents. With a properly functioning building trap, they don't get inside the home.

I have a building trap and vent on my house. I've never smelled an odor coming from it when I've been working in my yard near it. Today was a calm day and I spent a good deal of time raking, mulching, and on my knees planting bulbs in a flowerbed with my nose about 2 feet away from the vent and I didn't smell any odors coming from it.

[hausdok]

Hi,

I spent the first 21 years of my life in New York State and grew up learning how to build houses there. I'd never even seen a building trap until I saw one in a photo posted here, so, yeah, that would jive with the "it's up to the local AHJ" thing.

OT - OF!!!

M.

[Chad Fabry]

They seem redundant even with a building trap. At least if the trap plugs you'd have sewage in the garden and all would be normal until you noticed it maybe weeks later.

[Brandon Chew]

This piqued my curiosity and I've done a little more research into it. There is some speculation that building traps were originally required as a means to keep sewer rats from getting into the home. A more likely reason is that sewer gases can be foul smelling and corrosive. In situations where the generation of excessive sewer gases might be a problem, the building trap keeps them from corroding the building's plumbing (probably not much of an issue with ABS or PVC) or from stinking up the neighborhood as they are vented through the roof vents.

[Jim Katen]

Originally posted by Brandon Chew

This piqued my curiosity and I've done a little more research into it. There is some speculation that building traps were originally required as a means to keep sewer rats from getting into the home. . .

You can scratch that possibility off the list. Rats will happily swim through a trap that size. It won't even slow them down.

- Jim Katen, Oregon