Plumbing vents and operable skylights
My city requires plumbing vents within 10′ of an operable skylight to terminate a minimum of 3′ above the opening. I think this is a fairly typical requirement; I noticed that other cities in my area have the same requirement.
The code doesn’t state how you determine the height of the skylight opening; is it the low point or high point? Should I assume that since it is not specified, that high point is implied since when you open the skylight pretty much the entire area of the skylight is open? Therefore that is then determined to be ‘the opening’ with regards to the requirement. However, on the other hand, I’m thinking there’s a chance they may allow you to use the low point because the 3′ requirement may be high enough to take care of the differential between the high point and low point in most cases. Of course there’s the variable of differing roof slopes, which may be something that they don’t want to factor in…..
I’m more than likely going to call into my bldg. dept. with this question but thought I’d ask here first. Thanks for any info.
Replies
check in with blg dept
jonrossen wrote:
I'm more than likely going to call into my bldg. dept. with this question ...
That's a great idea.
we have something very similar here. it will be the highest point. they only thing you probablly have going for you if your going to try and argue that is that your inspector will most likely not get on the roof to measure it...
Sounds to me like unprofessional "roll the dice" advice. I'm not surprised.
At any rate, why cross the bridge on this issue after you have your vent and skylight in place when you can easily cross it before? By simply calling your building dept. and resolving your question beforehand you can approach it with the confidence that you work will not be re-jected or have to be re-done.
you really do have a hard time with reading comprehension
hence the adivce i gave dumbnuts...
Wow, some verball sparring over my skylight / vent question. I feel honored! :-)
Just to be clear, in case it wasn't in my original post, only the skylight is new. The vents are existing and if I totally remodel the bathroom, it won't be for another year or two. The skylight was done now because of timing; the house is being re-roofed. I did just enough planning and design for the future bathroom remodel to allow me to size and position the skylight and think about the kind of well that I want. In addition I'm hoping that the skylight will give me the motivation to go forward with the bath remodel sooner than later.
Yeah, after thinking about this I would think that high point of skylight is what is used; thanks for relaying your experience. I don't think I'm going to try and hope the inspector won't be measuring. I'd like to be in compliance because I think this is a reasonable code. However, to keep the vents in their current location and for them to be high enough, they will be freakishly high and really weird looking. As it turns out, I can move them; I didn't think it was possible at first. I can have them slope the allowable angle (> 45 degrees from horizontal) on the outside of the house and just be out of the 10' radius from the closest corner of the skylight.
glad you can re direct it.
Check to see if vents are allowable on the outside of the house. They aren't always allowed in cold areas because of frost plugging in the winter.
I don't that should be a problem here (west coast, SF area). My vents are now on the outside as well as my neighbor's and houses all around here have them. The examples I'm citing are very old houses and it could be 'existing non-conforming' but I have a difficult time believing that in my area they would be prohibited from being outside.
Even here in balmy southern Minnesota vents are allowed in outside walls (or at least were, as of about 20 years ago). Drains in an outside wall, of course, are a different matter.
Are they allowed outside the wall? That's what I was talking about. Inside an outside wall is different.
International Residential Code
The IRC, which has been adopted as the uniform building code by most States, requires a plumbing vent termination to be a minimum of two feet above the " top " of the sky light. Common sense would define the top as the upper most point of the opening, I think. I would suggest keeping the vent termination as far as possible from any opening, especially if the plumbing is connected to a private sewage system.
Thanks for relaying this info about the need to use the 'top' of the skylight. I've decided to move the vents and there is a solution that gets both vents just out of the 10' distance. I got sort of lucky in that there are no windows in the way for the rerouting of the vents and the corner window / bay popout that I have at the corner of the house is far enough away (> 10') that it won't cause any problems since I can't go any further than that for one of the vents.
Sons house has a 3" vent 10
Sons house has a 3" vent 10 ft above porch. Can smell it in the summer. 50 ft away from a opening skylight wold be more of a safe distance !! Even 15 ft away, you have an excellent chance of some choice indoor 'fragrances' during ;the summer.
Codes really overdo some things, this is one area that is not overdone.
A Law That's 100% Enforced
That is, the "Law of Physics."
WHY do you think the spacing is required?
I'll posit that you really don't want the skylight sucking sewer gas into the house. That sort of backdraft is all too possible. If anything, I'd err on the side of caution, and place the vent as far as possible from the skylight - and measure that height based upon the highest part of the skylight.
Thanks for the reply but.....
Whoa, you need to re-read my original question because the tone of your reply suggests that I'm unclear on why this code is necessary and that I don't understand its need to exist, and that I'm resisting complying with it or somehow being stubborn about the whole thing.. I *merely* asked how the '3' higher than operable skylight within 10' rule was interpreted with regards to top or bottom level of skylight. That's *all* I asked. At no point did I question the rule or suggest it wasn't necessary. I just wanted to know what was *required* by me by the code and then use my own judgement to come up with a design solution that worked while complying. As soon as I cut the opening in the roof after the skylight framing was done, I did notice the smell from the vent from time to time so I do have first hand experience as to what this code is about. I didn't feel that it was necessary to mention that in my first post, but I guess I should have done so in order to avoid getting unsolicited 'advice'.
opportunity for learning.......
There are vent terminal filters ( google Odorhog or Sweet air filters ) that will semi - purify the exhaust of an active plumbing vent pipe via charcoal activation.
The real value of this, and other forums is the sharing of tips, techniques, experiences, opnions, ideas, problems, issues, challenges, solutions, banter, and, general discussion. Readers visit with a variety of building skill levels; the smart ones are able to glean information and learn. I'm always fine with those who wander off topic - I'm in my 60's with 45 years of experience in the building trades and hold 5 licenses including master plumber, and, I know there is still much to learn...............
Septic Vent Filter Options
You can also look at http://industrialodorcontrol.com. They have a couple of options for residential septic odor.
Backwards Reasoning is All Too Common
For example, how many folks treat the highway 'speed limit' as if it were a MINIMUM?
It's almost gospel in the trades to attempt to do the least possible you can get away with. While these folks quite smugly assert that they've "met code," they've completely overlooked the introduction to the code, the very first few paragraphs.
These are the parts that say that the code is not an instruction book or design manual. When you build to 'code minimum,' you're using the codebook as your design manual.
I prefer a different approach. I prefer good design. It's been my experience that a good design invariable meets code .... while a 'code minimum' design is often a poor design .... and often doesn't meet code anyways.
Now, as to your vent ....
Every roof and every site is different. I'm glad you got a whif or two .... now you know what's at stake. While you were atop your roof, you may have noticed a thing or two about the way the winds act up there. For example, a collection of debris might suggest a 'dead spot' with poor air circulation. Or, as you poked your head over the ridge, you may have noticed a stiff breeze.
Use that information. Place the top of the vent stack where the wind is sure to carry the stink away. If that's a bit higher than what someone claims is 'the minimum,' so what?
Yes, I see where you are coming from. But you also have to be careful: You may come up with a design or idea that you feel is better than code minimum, but due to technicalities doesn't conform to code. You see, it's not always 'linear'. So, it's good to fully understand the code first.
Believe me, I had no intention of letting the code drive the design on this; but I did want to know what the code was. It's sort of like bounds testing in software testing. You want to explore the upper and lower limits to see where breakage occurs, just to know what you have on your hands. In this case, I was using the code as a starting point. Btw, the prevailing winds where I live are very obvious and the place where I'm moving the vents will be in a place where the winds will carry the fumes away more reliably.
A lot of times I confuse people about my intent when I ask questions about a certain subject. For example, they'll tell me that there may be 3 ways to do something. I'll then inquire about each of the 3 methods and most people think I'm asking the questions because I intend to use that specific method. So, when I ask about all 3 one by one, they think I've changed my mind twice. But what they don't understand is that I'm just exploring options, understanding the choices I have. Once I understand the 3 options fully, I can then think about it for awhile, then figure out which one I want to use, perhaps combine some if that's possible.
The venting and dissipation of septic odors can be influenced by many factors - topography, barometric pressure, prevailing winds, nearby structures, weather patterns & fronts, tree lines, mechanical devices, roof lines, septic tank activity, seasonal changes to nearby or overhanging flora & fauna, and more. Charcoal activated roof vent filters can be helpful, but, in severe cases when there is an interior, hidden odor source, a whole house trap installed where the main soil pipe exits the house, will provide a permanent solution to sewer odor.
In fact, a charcoal filter will eventually become loaded with odors and hence useless.
Getting Replacement Carbon
Filters like those found at http://industrialodorcontrol.com can last 3-5 years depending upon air-flow and hydrogen sulfide concentration. All the filters they have are able to accept replacement carbon that then gives you another 3-5 years.
If I were you ....
I would assume you should error on the side of going to teh high side unless you "love the smell of poop in the morning"
I think it's obvious that no one here likes the smell of sewer gas. In my case, the two existing vents that were within the 10' distance from the skylight were very problematic because not only were they in the 10' distance but they were very close (3.5' or so). So they were a problem functionally as well as not being code compliant.
To satisfy code AND eliminate the smell problem, I could have increased their height to the prescribed 3' above high point of skylight but that would have looked ridiculous. These vents were along the side of the house so they were close to the edge of the roof. They would had to be something like 6' high total to satisfy that height requirement. I would think that most people would think that having two vent pipes at the edge of a roof that were about as high as the ridge would look pretty ridiculous. They would have looked ridiculous merely satisfying code minimum and even more ridiculous 'erring on the side of being higher'. So, increasing the height was not a good option.
I found a great solution. The vents were combined and moved towards the front corner of the house and is pretty well hidden by a popout bay at that corner. This bay is one of those window seat deals that is in the corner of the front bedroom. There was a nice inside corner that we stashed the vertical rise of the vent pipe so it's hidden from the street. The entire side of the house looks a lot better now, so doing this for the skylight helped out the side facade as well.
The spot where the vent is relocated is a good one as the prevailing winds here pretty much blow west to east (from the water-SF Bay- to inland). My street is runs east/west so the the winds typically blow up the street; it will pick up the output from that vent on the corner just fine. I don't expect any issues with the vent moved to this location.
The location is also perfect to satisfy code; I measured exactly 10'-4'. I'm also a tad over 10' from a dormer window that is @ the front of the house.
I still haven't done anything to the bathroom ceiling, so I can stand on top of the ceiling joists and look out over the roof through the skylight opening. At the low end, the roof hits me at about knee to mid-thigh, so my nose is pretty high, much higher than it would be when the skylight is in normal use. I was out there a few times for a minute or two and didn't smell anything with the new vent location. I could smell sewer gas easily before we moved the vents.
PROBLEM: Solved! Thanks, everyone for your input
I ran ..
I ran all of my vents to within 2 or 3 feet of the ridge. some were run up in the rafter bays in cathedral ceiling areas, kind of a pain. No snow sliding down to break teh vents off and no odor. Nice to be safe. Glad you have figured out a plan for your job.