Any length max on horiz. vent branch (to get to main stack)?

13 years ago

Hi,

First, is there an exact name for the horizontal piece that multiple secondary vent stacks terminate in, that then runs over to the main vent stack?

As depicted in the bottom, rightmost picture titled "Terminating into header" on this page:

http://www.3dplumbing.net/ontplumbing/vent_stack.htm

Is it called a "vent header"?

(Asking because when I Google search on "vent header", I get pages that don't match in their descriptions. :-)

And my main question: Does the code put a restriction on how long that horizontal piece can be?

If I have a secondary stack vent running up to the attic, can I terminate it in a horizontal piece that might run 25 feet over to the main stack?

Or would I have to split up that horizontal distance with another stack vent in some way?

If it makes a difference, I'm in MA and I think we're under the UPC. I'm trying to learn enough that I have the right terminology to even see what might be feasible to do in my old house.

Thanks in advance!

Lee

Comments (7)

manhattan42
13 years ago
See the link below for Massachusetts CMR Plumbing Code.

Pay particular attention to 'headers' and Table 2 for vent pipe sizing.

Here is a link that might be useful: Mass UPC Vents and Venting
la_koala
Original Author
13 years ago
Thanks manhattan42! Thanks both for posting the link and for confirming that "header" is the right term to pay attention to.

I always have difficulty reading these ordinance-type of things. For example, it seems that a word or punctuation is missing from this one:

10.16 (5) (d) 2 and 3 reads:
2. The vent header shall connect to a vent extension through the roof.

3. When more than two four-inch soil or waste stacks are connected the vent header extension through the roof shall be five inches in diameter.

Does #3 really mean in essence:
"When more than two four-inch soil or waste stacks are connected to the vent header, the vent extension through the roof shall be five inches in diameter."

(Notice the addition of the word "to" and a comma added after "vent header" above).

I'm asking because #2 uses both the phrases "vent header" and "vent extension", and states that the vent extension goes through the roof. I can picture that.

But in #3 as written in the Mass UPC, it introduces what looks like a new phrase, "vent header extension" going through the roof.

And hence my confusion. :-)
It makes more logical sense (to me anyway) that if you've got more than 2 4-inch stacks basically connected together, that you'd want a higher diameter pipe as the single guy going out through the roof. But that #3 isn't communicating that well.

Thanks!
Lee
Related Discussions
Second Air Return Length
Q
Comments (7)
I'm not sure I got the 'message' across, but we were not thinking of entering the chimney chase - at all. The chimney enclosure outside presents a location on which to merely add another corner on the outside of it (making sure the original chimney enclosure remains sealed and intact), and thus, having a new adjacent chase totally empty in which to possibly run an air return duct down if choosing that option. But, still I'm not sure code would even allow that. While a friend of mine is pushing that option, I don't like this idea myself personally because of the length involved going to outside end of the house to go down, and then going back toward the center areas of the house in the crawlspace. That would add about 14 feet to the overall run. I'm just not sure what effect that would have on the benefits. However, it has come to mind another idea I can try, if I'm really curious about the length or effects of it in a second return run. I can simulate the second return with minimal work and try it out. Simply connecting a second return duct to my modified furnace plenum (when I get that done), I will then run the full length of the second duct I plan to use, out the attic door and down the stairs and to a chosen location, simulating the turns and bends all inclusive of the enclosed run that I would wish to make. Then I would put a filter on the end of it (temporary mount), and run my furnace system in various tests. I have an anemometer coming in the mail, so once it gets here I can use it to test the flow pressure at each main branch, original upstairs, and then my test duct downstairs. I will also be able to feel the actual return pressures for myself and compare them. From this type of simulation I should be able to at least ascertain whether or not such a return system can be adjusted for balance, and what the net benefits might be after using such a length. So that's what I plan on trying, without actually committing to any permanent options or modifying any structure yet. As always I still appreciate any thoughts and would like a pro to chime in anytime. Thanks again everyone.
...See More
New Master Bath venting help w/ pictures
Q
Comments (9)
Before we begin, to answer one of your questions, you can find the UPC vent size DFU table on the Vent page in your code check. It is listed as table 11 on the right hand side of the page. I can see a number of small problems on your proposed layout. 1. On the branch drain which is serving the W.C. & shower you show a cleanout on the end of the line with a wye & 1/8bend and a fixture arm to the shower, then another wye & 1/8 bend with a short horizontal offset to the vent riser. In that configuration you have a horizontal offset on the vent below the floor, but code prohibits any horizontal offsets on a vent until the vent reaches an elevation at least 6" higher than the flood level rim of the highest fixture served by that vent, which in this case you be 6" higher than the W.C. bowl rim. You could place the shower arm wye between your proposed location for the cleanout and the vent. In this manner the vent would be on the downstream side of the shower arm and assuming the vent rises vertically you would be ok. For the branch serving the W.C. and the shower the combined fixture load is 4dfu's and an 1-1/2" vent is rated for up to 8dfu's, but note the subscript 2 beside the dfu number. If you look at the second exception on the chart it says NO W.C. A wc requires a 2" vent. On that branch you only need a 3" drain until you reach the wye at the WC. From the WC wye to the shower and vent it can be 2" but be careful here as well. On the top of the drawing it shows the 2" vent has a horizontal offset to the vent through the roof. If any horizontal offset on a vent line exceeds 3' the entire vent line must be increased one nominal trade size. That means the entire vent would then be 3" and the drain line downstream from that vent opening would also need to be 3". If you have enough vertical clearance in the attic space you could make that offset rise at a 45degree angle because in plumbing any line that rises at an angle of 45degree or greater is said to be a vertical line. The lavatories are rated at 1dfu which would be an 1-1/2" drain line, but code will allow us to increase the drain line by one nominal trade size, which would then be 2". A 2" fixture arm is allowed to go 5' from trap weir to vent opening. I roughly scaled your drawing and you should be able to run a 2" line from the tub and tie the vent in at 5'. The vent should then rise between the two lavatories very close to the left hand lav as facing the lavs from the front. You could then run a 2" over to the other lav and still be under the 5' maximum, thus you would not need two vent risers on this wall. The total dfu load for the tub and two lavs is 4dfu's which could be vented with an 1-1/2" line, but since you have a horizontal offest greater than 3' the vent must be increase one nominal trade size, which would be 2" which you have already specified.
...See More
allowable number of fixtures on one stack?
Q
Comments (6)
There are no limits to the actual number of or types of fixtures that may be connected to a stack. Instead of limits to the number or types of fixtures the code has a table listing all the types of fixtures that may be connected to a DWV (drain, waste & vent system) and the table defines the minimum drain & trap size for the fixture and it defines a specific DFU (drainage fixture unit) load value for the fixture. The code then has another table that lists all the listed pipe sizes and the maximum allowable load on each specific size of pipe for both vertical and horizontal application, expressed in dfu's. By example, a lavatory bowl is listed as requiring a minimum 1-1/4" drain & trap and it is assigned a load value of 1 dfu. A WC (water closet -commonly called a toilet) that has a flush of 1.6gallon/flush or less is listed as requiring a 3" drain and it has a load value of 3dfu's. When designing the DWV system we begin by making a list of all the fixtures in the house and computing the total dfu load. From that we can check the pipe size chart to determine the size of the house main drain and house sewer. We then lay out the branch lines from the main drain to each respective fixture or fixture group such as bathrooms, kitchens, laundry etc and we compute the dfu load for the branch. Here again, we check the pipe size table to determine the size of branch pipe required. The exception being that if any fixture in the group is required a line larger than the dfu load table requires, we must use the line size required by that fixture. An example,, A tub/shwer combo is 2dfu's, the lavatory 1dfu and the WC is 3dfu's for a total of 6dfu's. The pipe size table says a 2" pipe may carry up to 6dfu's, however because of the size of solids in the discharge from a WC code requires a WC to have a 3" drain and we cannot reduce the size of a line in the direction of flow so we would be required to make a branch serving a WC with 3" pipe. Next we have to consider the venting. A length of pipe running from a fixture trap to a vent is defined as a "Fixture arm" while any length of horizontal pipe from a vent downstream to the stack or main drain is defined as a "Vented Branch". When attaching fixtures to a vertical stack we may not attach any fixture to the stack by means of a fixture arm if it is below a WC being served by the stack. by example, your stack is serving a WC on the second floor so you may not connect a fixture arm directly to the stack on the first floor. The option would then be to install a separate stack for each floor or you could install a vent between the fixture traps on the first floor and the point where the line ties into the stack. In this configuration, the section of pipe from the trap to the vent is a fixture arm, but the section from the vent to the stack is a vented branch, which may be attached to the stack.
...See More
washing machine connect to plumbing stack directly?
Q
Comments (5)
In order to properly answer your question we need to begin with some basic code definitions. TRAP-by code definition the trap is the U shaped section of the fitting that retains water to affect an air & gas tight seal between the fixture and the sewer line to prevent sewer gas from entering the structure. TRAP WEIR- just as the weir of a dam is the point on the spillway where water can overflow the dam, the trap weir is the physical point on the discharge side of the trap U section where water passing through the trap can spill out of the trap and into the trap tailpiece & drain line. FIXTURE ARM or WASTE ARM- While most people think of a fixture arm as the short section of pipe extending out of the wall where a sink trap is connected, that is not correct. The fixture arm is the total developed length of pipe from the trap weir to the vertical stack or vented horizontal drain line. Understanding that it is only one line, it then stands that the line must serve as both the drain & vent for the trap. Under the International Residential Code (IRC) the bottom of the fixture arm at the trap weir may not be higher than the top of the pipe at the vent opening, thus we can mathematically compute the maximum length of a fixture arm by dividing the diameter of the pipe by the pitch of the run. Example- The code standard for a bathtub drain line is 1-1/2" and all lines 3" or less are required to have a minimum pitch of " per foot thus the maximum length of the tub fixture arm would be 1.5" / .25Â = 6Â but be very careful here. Keep in mind that the top of the pipe at the vented drain cannot be lower than the bottom of the pipe at the trap weir so if you mistakenly run the line with a greater pitch, it will shorten the allowable length of the line and under no circumstances may you have a vertical offset. In addition, the code says, "Maximum developed length of pipe". (I have seen instances where you get a real hardnosed inspector and he/she will make you also compute the fitting losses. By example a 1-1/2" 1/8bend has a fitting insertion loss of 6" which means that while the 1/8th bend is physically only about 3" long, you have to compute it as 6"). The Uniform Plumbing Code (UPC) began with basically the same mathematical maximum as the IRC but then they de-rated the maximum lengths by about 40% thus we must either memorize the lengths or keep the code table at hand. UPC Table T10-1 1/14"ÂÂ2Â6" 1-1/2"Â..3Â6" 2"ÂÂÂ.5Â 3"ÂÂÂ..6Â 4" or larger 10Â The minimum length of a fixture arm when measured from the trap weir to the vertical riser, stack or vented horizontal drain is to be 2x the diameter of the fixture arm pipe. Now to answer your question; the tie in can be made at any convenient point on a stack or horizontal line, except, an un-vented fixture arm MAY NOT be connected to a vertical combined waste & vent stack if there is a watercloset (toilet) discharging into that stack at any point above. The solution would then be to install a separate vent on the line between the trap and the combined waste & vent stack. By doing so the line from the trap to the vent is classified as a fixture arm, but the line downstream from the auxiliary vent to the combined waste & vent stack is now classified as a vented branch and that may be connected to the stack but be careful here as well. The auxiliary vent must rise to an elevation at least 6" higher than the flood level rim of the highest fixture served by the combined waste & vent before you can tie the vent into the stack.
...See More
manhattan42
13 years ago
See the link below using the image from your first post.

The 'header' is the horizontal pipe that connects the vent stacks.

The 'vent header extension' is the vertical vent pipe that extends up from the vent header through the roof.

Here is a link that might be useful: {{!gwi}}
la_koala
Original Author
13 years ago
OK, thanks for clarifying that about the "vent header extension" piece.

You've been extremely helpful. If you don't mind, a follow-on question:
Can the 'header' horizontal pipe connect to an existing main stack (soil stack) which already terminates through the roof into open air, connecting above the point where any fixtures are?

Or is the code saying that the header configuration always require the vent header extension and terminating itself through the roof, requiring a second pipe through the roof?

My situation is that the main stack is at the front of the house (second story full bath, soil and vent for that bath, no other fixtures above the second story). The venting for the kitchen in the rear is not up to today's code (outside vent up the side of the house). I'd like to be able to run a new stack vent for the kitchen in that rear part of the house, and then connect that vent to a header running across the attic space above the second story to connect to the main stack vent in the front.

I'd really like to avoid making another hole in the roof and stay within code--thus my question of whether it is allowable to connect the header to the existing main stack vent, in the attic space that exists above any and all of the fixtures on any vent.

I hope my question makes sense. It seems that the last time plumbing was done in this house was over 50 years ago and the external stack is no longer allowed in my area.

Thanks!
Lee
manhattan42
13 years ago
Talk to your local plumbing code inspector.

I am not that familiar with the Mass. UPC. We use the IPC in my jurisdiction and the codes are different.

It appears that the UPC requires the 2nd stack penetrating the roof if the existing vent is not large enough to serve all fixtures and their DFUs.

Regradless, you would actually produce a better more efficient drainage system if you installed the 2nd vent extension through the roof imho.
la_koala
Original Author
13 years ago
Hi manhattan42, thank you so much for replying.

And thanks for your last thought about the efficient draining. I hadn't thought of looking at it that way, and that's a good "pro" on the side of going straight through the roof at that spot. (I'm going to need something to tell my spouse--who's queasy about leaking roofs--why putting another hole through the roof is better than the alternative.)

While I did have a brief meeting with our plumbing inspector a week ago (and just to see if the existing rear external vent was viable if we're redoing the kitchen) he seemed reluctant to talk to me, the homeowner directly. He kept saying I should hire the plumber and then he'd be happy to meet with the plumber.

(Which made me a bit dismayed that he only wanted to speak with plumbers, because a few years ago we hired a licensed, neighbor-recommended, well-known local plumber to put in a washing machine hook-up in the basement. We thought he had pulled the permit and was going to do the work to code. That guy put in an air admittance vent -- and now I come to find out from my chat with the inspector that the air admittance vents are not allowed! So all that work has to be re-done. If an inspector is truly going to only speak with the plumber, then I figure I'd better get educated on what's allowed and what's not so that I ask the plumber the key questions before I hire him/her and can feel confident that the right things will be done. Once bitten, twice shy.)

manhattan42, I appreciate all the info you've given--it's helped immensely!

Thanks again,
Lee
manhattan42
13 years ago
I believe Mass. is one of those states where plumbing must be done by a state licensed plumber.

That is why your inspector doesn't want to talk to you, the owner.

As far as your story about the air admittance valves, they are permitted under the UPC but only with the permission of the plumbing inspector and generally only when no other viable venting alternative exists.

Sounds like your plumber on the washing machine did not ask about the AAV nor call for any inspections...and why the inspector was PO'd...with every right to be.

Any length max on horiz. vent branch (to get to main stack)?

Comments (7)

manhattan42

la_koala
Original Author

Related Discussions

manhattan42

la_koala
Original Author

manhattan42

la_koala
Original Author

manhattan42

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

Any length max on horiz. vent branch (to get to main stack)?

Comments (7)

manhattan42

la_koalaOriginal Author

Related Discussions

manhattan42

la_koalaOriginal Author

manhattan42

la_koalaOriginal Author

manhattan42

COMPANY

BUSINESS SERVICES

GET HELP

CONNECT WITH US

la_koala
Original Author

la_koala
Original Author

la_koala
Original Author