Panels over vent pipes?

Our roof is being measured this afternoon for our 7kw system. The radon and sewer line vent pipes that extend about 18" through the roof in places where I would like to have some panels. Is there any reason why I shouldn't cut off these pipes to about 4" long so the panels can mount over them, still leaving about 2" of clearance between the top of the pipe and the underside of the panel? I asked my plumber about it this morning and he didn't see why it would be a problem, but of course he doesn't know anything about pv. He said the only reason they are so long is so they don't get covered with snow. I'll ask my installer about it this afternoon as well, but would be happy to glean from anyone else's experience and/or expertise too.

Strawbale

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panels over vent pipes?

    I'd recommend against it. Even just cutting the pipes short will reduce the "chimney effect" that allows these vents to, well, vent properly. It's about having air flow over them that causes pressure reduction to draw the gases out. Admittedly it doesn't have to be much, but there are standards (which vary between areas) and your plumber should know this. It's not as dangerous as restricting an actual chimney flu, but it will reduce the performance of the vents and possibly violate loal code. Also, some of the gasses that come from the sewer vent may prove to be corrosive to the panel mounts.

    But you could look into relocating the vents; a couple of elbows and some more pipe they could possibly be brought out through a different location in the roof. Perhaps you'd be allowed to do this above the roof; running pipe outside up under the panels 'til it clears.
  • strawbalestrawbale Solar Expert Posts: 29 ✭✭✭
    Re: Panels over vent pipes?

    Thanks, I'll run this by my installer this afternoon too. I did think of rerouting the pipes above roof, but with the height of the boot I 'm not sure how much space would be needed for the fittings. I'm also not sure about how a horizontal piece of pipe and fittings would restrict air flow from the vent pipes. It could be challenging to find the proper degree ell to take the extension up the roof under the panel on a 4/12 roof.

    Strawbale
  • ambyamby Registered Users Posts: 13
    Re: Panels over vent pipes?

    I am similar situation. got between 2 and 5 vents in the way. also got 1 powered vent fan!
    I just assumed by default they have to be moved and was going to get estimate for under-the-roof (in attic) relocate.
    as Marc sadi, I dont expect it to be much complexity other than a few elbows and some more pipe length. as is (I checked in attic), these are not straight routed up and are having few bends in attic.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panels over vent pipes?
    amby wrote: »
    I am similar situation. got between 2 and 5 vents in the way. also got 1 powered vent fan!
    I just assumed by default they have to be moved and was going to get estimate for under-the-roof (in attic) relocate.
    as Marc sadi, I dont expect it to be much complexity other than a few elbows and some more pipe length. as is (I checked in attic), these are not straight routed up and are having few bends in attic.

    Careful: elbows add up. Too many will also reduce air flow to unacceptable levels. When you calculate heating ducts, for example, one 90 bend is like adding 13' of pipe! It may be necessary to remove the existing elbows, and re-route from the straight vertical pipe.
  • icarusicarus Solar Expert Posts: 5,129 ✭✭✭✭
    Re: Panels over vent pipes?

    I would NOT put the panels over the vents. I think you are asking for trouble. That said, in the real world, the venting size requirements for plumbing vents are WAY over sized. If you have access into the attic, cut them below the roof line, reroute them to the other side of the roof. If you have to add lots of pipe length you could up size the pipe size from 3" to 4" or 4" to 5". If you have galvanized or cast iron pipe, you can still cut the with a sawzall and transition to plastic with no hub clamp fittings.

    If you can't get to the attic, you could put an elbow on the pipe above the roof line (combination of el's!) to run the pipe up the roof line towards the peak and have it daylite above the panels.

    Tony
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panels over vent pipes?

    To expand on what Tony said; sometimes the vents work better when they're "shrunk" for the last few feet. Most of the local code regs are based on sticking a 4" waste stack through the roof; no consideration for what's actually going on in terms of air flow. Only recently, in fact, have they 'discovered' the advantages of venting sinks and tubs. Well, "recently" in terms of my life span. :p
  • SlappySlappy Solar Expert Posts: 251 ✭✭✭✭✭✭
    Re: Panels over vent pipes?

    the sewer vent pipes produce methane gas, highly explosive! Not only that, if you ever need to clean out the pipes. "rotor rooter" the panels will be in the way?
  • mike95490mike95490 Solar Expert Posts: 8,288 ✭✭✭✭✭
    Re: Panels over vent pipes?

    May as well consider the snow problem for the panels too. You don't want too much weight on them, and you don't want "dam" to form under them.

    re vent pipes, I consoldated mine in the attic, and ran 1 thru the roof. All to code, and the plastic drains don't clog up nearly as much as iron.
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  • strawbalestrawbale Solar Expert Posts: 29 ✭✭✭
    Re: Panels over vent pipes?

    Thanks for all your responses. My installer also counseled against simply cutting them off under the panels. The direction I am going now is to re-route them with elbows on top of the roof as icarus suggested. I need to play with what is available to see how I can match the 4/12 pitch while staying within the 6" panel clearance. I may need to try bending some of the pvc with a heat gun as well.

    I suppose rerouting the pipes in the attic would be ideal, but I really don't want to make more holes in my roof and need to close the existing ones, since my roof is only six years old. One of the guys measuring my roof this afternoon said the vents on his fairly new house don't even come through the roof. They all go up to the ridge vent and stop there inside the house. He said his whole development is that way.

    Strawbale
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panels over vent pipes?
    strawbale wrote: »
    One of the guys measuring my roof this afternoon said the vents on his fairly new house don't even come through the roof. They all go up to the ridge vent and stop there inside the house. He said his whole development is that way.

    Strawbale

    That wouldn't meet code anywhere that I know of. Venting into the attic is a distinct no-no, and that is essentially what they're doing. It is common to run vents sideways through an attic space and come out the gable end.
  • icarusicarus Solar Expert Posts: 5,129 ✭✭✭✭
    Re: Panels over vent pipes?

    Straw bale,

    Couple of things. First, ABS/PVC elbows come in every angle from 11.25/22.5/45/90 degree increments, so you can make virtually any angle you wish.

    That said, if you have the option of doing it in the attic I would highly recommend doing so. Patching one simple hole is only a matter of screwing in a shot of plywood with a strong back on it, and a shingle or two. Almost nothing is easier than flashing in a pipe with a rubber flashing boot. Shingles over the top ~2/3 of the flashing, flashing over the top of the bottom 1/3, with a flat bar and hammer takes a few minutes.

    The advantage of moving it in the attic, is a nice clean install. If you run the vent up the roof on the outside, you will need stand-offs etc to keep it off the roof.

    As for "roto rooting" drain lines from the roof vent. It CAN be done, but that it what cleanouts are for. A roof vent may have dozens of Els and Tees between it and any clog. Also, as noted, plastic pipe is very much less prone to clogging relative to cast iron/galvanized.

    Tony
  • LucManLucMan Solar Expert Posts: 226 ✭✭✭
    Re: Panels over vent pipes?

    The main reason for vents is to prevent a vacuum when the water is running down the drains, and to keep all pressures in the drainage system at atmospheric. With out a vent when you flushed the toilet it would be like holding your finger over a straw nothing would flow.
    Every house should have house trap to prevent methane from entering the house from the septic or city sewage system, this is also vented.
    Vents are raised above the roof to keep the snow from plugging them.
  • icarusicarus Solar Expert Posts: 5,129 ✭✭✭✭
    Re: Panels over vent pipes?

    Just to clarify, I think that vents are above the roof to help induce a draft, as well as to make sure that any sewer gas is above any opening window or door.

    As for a a "whole house trap" A proper septic tank serves as a proper trap, but on a house connected to public sewer, I have never heard of a "whole house trap". Every fixture should have it's own trap to seal gas in the pipes. "P" traps, drum traps and toilets are all effective traps. In certain instances seldom used drains, especially floor drains, require "trap primers" that leak a bit of water into them to keep them filled. Water in unused traps can dry out over time, and can indeed be "sucked" out if you have improper venting. I have even seen water in a toilet get sucked out of a toilet trap in a extremely high wind!


    If you ever smell sewer gas in your house, try pouring a bit of water in a seldom used trap, like the one in the utility sink in the laundry room, or the guest bath shower.

    Tony


    PS Getting a bit off the track here,,, sorry
  • strawbalestrawbale Solar Expert Posts: 29 ✭✭✭
    Re: Panels over vent pipes?

    Thanks again for all your input. As I've thought more about this I want to check into moving the vent pipes (1- 3" sewer and 4- 2" radon) a bit further up the roof, that is reroute them in the attic, patch old holes, etc. I need to check with our local code officials to see if I can indeed bring the four radon pipes together in the attic and only take one through the roof. I am still leary of doing this on my own, I don't want my roof to leak!

    What I don't understand-- if radon gas is the heaviest gas and 8 times heavier than air, why is it vented out the roof?!? Our house is on a the side of a hill. Why wasn't it vented out to a lower place down the hill? My wife asked this numerous times while we were builiding, but we never got an answer. My guess is that our pipes are simply in place in case we need to add a fan, and that as they are now they aren't doing anything. If that is the case, why not cut them off in the attic and we can always take them out through the roof if we ever need to add a fan.

    Strawbale
  • mike95490mike95490 Solar Expert Posts: 8,288 ✭✭✭✭✭
    Re: Panels over vent pipes?
    LucMan wrote: »
    Vents are raised above the roof to keep the snow from plugging them.

    I think there has got to be another reason - in LA and San Diego, where there is little chance of snow accumulation (well, before *Climate Change*) code requires vents 12" above roofing.
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  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panels over vent pipes?

    Vents both allow intake of air to facilitate water drainage and allow escape of harmful gases. The sizing and positioning of the vents affects the change in pressure inside the pipe, which can go from negative to positive depending on what is happening both outside and inside the pipe.

    I'm not going to render my opinions on whole-house traps (required by some municipalities) and radon venting. I'd be even less popular if I did. :p
  • icarusicarus Solar Expert Posts: 5,129 ✭✭✭✭
    Re: Panels over vent pipes?

    Talk to a local HVAC or plumbing contractor about the Radon thing, or talk to you local building official. When I used to build custom houses we were required to place a Radon detector in every new house. This consisted of a kit you left in a kitchen drawer, which the homeowner then send to the testing agency after several months of living in the house. I never hear of anyone having had enough radon to do a thing about it.

    I think you may be on to something thinking that the vent may be there in case you have to add a fan.

    Tony

    PS I applaud the idea of moving the vent. Doing the roof patch really is easy.

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  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Panels over vent pipes?

    http://en.wikipedia.org/wiki/Drain-waste-vent_system


    "Air admittance valve

    Air admittance valves (AAVs) are pressure-activated, one-way mechanical vents, used in a plumbing system to eliminate the need for conventional pipe venting and roof penetrations. A discharge of wastewater causes the AAV to open, releasing the vacuum and allowing air to enter plumbing vent pipe for proper drainage. Otherwise, the valve remains closed, preventing the escape of sewer gas and maintaining the trap seal. Using AAVs can significantly reduce the amount of venting materials needed in a plumbing system, increase plumbing labor efficiency, allow greater flexibility in the layout of plumbing fixtures, and reduce long-term roof maintenance problems associated with conventional vent stack roofing penetrations.

    While some state and local building departments prohibit AAVs, the International Residential and International Plumbing Codes allow it to be used in place of a vent-through-the-roof. AAV's are certified to reliably open and close a minimum of 500,000 times, (approximately 30 years of use) with no emanation of sewer gas; and some manufacturers claim their units are tested for up to 1.5 million cycles, or at least 80 years of use. Air Admittance Valves have been effectively used in Europe for more than two decades. U.S. manufacturers offer warranties that range from 20 years to lifetime."
  • strawbalestrawbale Solar Expert Posts: 29 ✭✭✭
    Re: Panels over vent pipes?

    I contacted my building code officer today and was up on the roof. The vent pipes are exactly the opposite of what I thought. The one 3" is radon and the four 2" are sewer. The building code officer said I could consolidate the four sewer pipes in the attic into one 3" and take that through the roof. So why did my plumber not do that rather than have four pipes going through the roof?!? So I intend to do that and move both 3" pipes a few feet up toward the ridge.

    Strawbale
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panels over vent pipes?

    dwh is referring to what the trade calls "cheater valves". They may technically be allowed, albeit not in some places, but aren't usually used except in tight situations where normal venting isn't possible - like "island" sinks. Some places allow them for any/all sink venting, but require the main stack to vent normally.

    It's all about them darn local codes! :p
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Panels over vent pipes?
    strawbale wrote: »
    I contacted my building code officer today and was up on the roof. The vent pipes are exactly the opposite of what I thought. The one 3" is radon and the four 2" are sewer. The building code officer said I could consolidate the four sewer pipes in the attic into one 3" and take that through the roof. So why did my plumber not do that rather than have four pipes going through the roof?!? So I intend to do that and move both 3" pipes a few feet up toward the ridge.

    Strawbale


    It's quicker (cheaper) while roughing in to just run a straight pipe up and out.

    Or as straight as possible I guess - I've seen some pretty twisty vent pipes.
  • icarusicarus Solar Expert Posts: 5,129 ✭✭✭✭
    Re: Panels over vent pipes?

    Easier and cheaper to got straight as DHW suggest. As for Air intake valves. I have used them for island sinks where conventional venting isn't possible, but I think that conventional venting is a better/cheaper more reliable solution, although I think the square inch requirements are pretty excessive.

    Tony
  • strawbalestrawbale Solar Expert Posts: 29 ✭✭✭
    Re: Panels over vent pipes?
    icarus wrote: »
    Easier and cheaper to got straight as DHW suggest.

    But considering four holes through the roof, rather than one with all the flashing and potential leaks 20 years down the road, as well as the aesthetics of 4 vs. 1, isn't the "straight up and out" rather short-sighted?

    Is easier snaking in the case of a clog another reason for not bringing them all together? In other words, do I need to keep any eventual snaking in mind when I bring these 4 into 1 before going through the roof?

    Strawbale
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Panels over vent pipes?
    strawbale wrote: »
    But considering four holes through the roof, rather than one with all the flashing and potential leaks 20 years down the road, as well as the aesthetics of 4 vs. 1, isn't the "straight up and out" rather short-sighted?

    Is easier snaking in the case of a clog another reason for not bringing them all together? In other words, do I need to keep any eventual snaking in mind when I bring these 4 into 1 before going through the roof?

    Strawbale

    You're right; connecting all four into one is more sensible. It's just that when they built the place the cheapest and easiest thing to do was four holes in the roof.

    As for clean-out, this isn't done from roof vents. Not much point in 'snaking' several feet of pipe that can't possibly have any clog in it. There is usually a "clean-out" someplace lower down. There should be a clean-out someplace lower down. You never know the way some places get built.
  • icarusicarus Solar Expert Posts: 5,129 ✭✭✭✭
    Re: Panels over vent pipes?

    No one snakes from a roof vent. There should be clean outs at strategic locations, additionally there should be clean out just outside the building line. As has been suggested, it is quite rare to need to snake pipes in a modern house. (Sewers are another matter due to roots/settling etc) With proper pitch and plastic pipes clogs are extremely rare. Bath tub/shower/teenage girls sinks accepted, as hair caught in the drain mechanism is THE leading cause of drains clogging.

    Tony
  • mike95490mike95490 Solar Expert Posts: 8,288 ✭✭✭✭✭
    Re: Panels over vent pipes?
    strawbale wrote: »
    But considering four holes through the roof, rather than one with all the flashing and potential leaks 20 years down the road, as well as the aesthetics of 4 vs. 1, isn't the "straight up and out" rather short-sighted?

    Is easier snaking in the case of a clog another reason for not bringing them all together? In other words, do I need to keep any eventual snaking in mind when I bring these 4 into 1 before going through the roof?

    Strawbale

    The plumbing installer wants to get to the next job fast. He's not a roofer. Let someone else solve that leaky problem.

    Snakeing - makes sure you can run a snake down the pipe and to the main. No "T" joints that would stop a snake.
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  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Panels over vent pipes?

    Actually, it's pretty common for lowbuck drain snakers to hop up on the roof and ream down through the vents. It's often quicker, since it saves on problems like finding and digging up cleanouts and breaking pipes while trying to unscrew the cleanout plug.
  • tallgirltallgirl Solar Expert Posts: 413 ✭✭
    Re: Panels over vent pipes?
    dwh wrote: »
    Actually, it's pretty common for lowbuck drain snakers to hop up on the roof and ream down through the vents. It's often quicker, since it saves on problems like finding and digging up cleanouts and breaking pipes while trying to unscrew the cleanout plug.

    It's also a lot easier to snake DOWN into whatever is clogged than try and get your head under a vanity or kitchen counter to make sure the snake isn't getting all kinked up going in sideways.
  • strawbalestrawbale Solar Expert Posts: 29 ✭✭✭
    Re: Panels over vent pipes?

    I finished consolidating my four 2" sewer vent pipes to one 3" in the truss area. Routed that as well as the 3" radon vent piper further up toward roof ridge, through and flashed. Patched and shingled the five holes. Thanks for your encouragement. It was easier than I thought, just time consuming. Now to be patient until my pv installer arrives....

    Strawbale
  • icarusicarus Solar Expert Posts: 5,129 ✭✭✭✭
    Re: Panels over vent pipes?

    Very good!

    Tony
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