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Author Topic: Vent Pipe Sealing  (Read 2175 times)
BC Bus
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« on: December 01, 2011, 10:06:02 AM »

I am getting ready to run a black water tank vent pipe through the floor and up through the rood of the ol GMC 4108.   I'm sure you can provide me with ideas on seals and sealing to the outside roof, and vent caps, and size of pipe.

Thanks

Bill
Gresham, Or
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Ace
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« Reply #1 on: December 01, 2011, 10:18:27 AM »

This has been beat to death but save yourself the worry of leaks and just run it out the top of the tank and then straight down thru the floor. Regardless of what people say that it can't be done, I'm still using mine after about 8 years and no smell or problems!
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Ace Rossi
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« Reply #2 on: December 01, 2011, 10:46:30 AM »

I agree with Ace.  5 years and no smell or other problems.
  Big John
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bevans6
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« Reply #3 on: December 01, 2011, 10:58:05 AM »

Y'all re-wrote the periodic table?  Methane is lighter than air, it rises.  It is trapped inside the tank unless there is a way for it to get out.  If you don't have a rising vent, then it either just accumulates or it gets out past the toilet seal into the bus.  

Your call on if that is good or not...

This is, btw, the synopsis of the "beat to death"...    Grin

Brian
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« Reply #4 on: December 01, 2011, 11:01:32 AM »

To the question:  you can buy a purpose made vent pipe sealing flange at the RV store.  It seals to the roof with adhesive sticky tape and around the 1.25" pvc pipe and usually has a little cap or other topper to keep the rain out.  Some have venturi's that are supposed to suck a vacuum in the tank when driving, etc.  Lots of choice.  You can also get little fans to put in the vent line.  Iffy if they actually do anything but make you feel better...

Brian
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« Reply #5 on: December 01, 2011, 11:22:43 AM »

Too funny but it is what it is
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Ace Rossi
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« Reply #6 on: December 01, 2011, 11:28:10 AM »

Ace, my vent pipe runs into the rear wheel well.  It has yet to bother me enough to rise to the top of the fix-it list.  So I have yet to practice what I preach...   Grin   In self defense I can only say that the previous owner (a high school teacher, yet) ran it into the wheel bay...

Brian
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BC Bus
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« Reply #7 on: December 01, 2011, 11:36:51 AM »

I guess I didn't know there were so many opinions on this topic.   I have decided to definitely run mine up through the roof so I will go buy a flange and vent top and do it to it.  Not that hard to do so why not.

Thanks for your input.

Bill
Gresham, OR
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« Reply #8 on: December 01, 2011, 11:39:46 AM »

You Mean a real honest to goodness teacher changed the periodic table? Shame on him!
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Ace Rossi
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« Reply #9 on: December 01, 2011, 11:55:41 AM »

I got two of these off of Ebay for less than $10, including postage.
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Dr. Steve, San Juan del Río, Querétaro, Mexico, North America, Planet Earth, Milky Way.
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« Reply #10 on: December 01, 2011, 12:32:24 PM »

I used 3m 5200 sealant at the roof penetration. Don't have anything on the end of the pipe yet, except a temporary cap to keep the rain out during winter storage. No leaks. Just make sure the penetration hole is a close fit.
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« Reply #11 on: December 01, 2011, 01:47:44 PM »

I used a flange designed for use on metal roofs. It has a rubber boot that goes around the pipe and seals around the pipe and will move if necessary then seal  the perimeter with any adhesive that you like --- personally I like the polyurethane from PL that you can pick up at home depot.

HTH

YMMV

Melbo
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Bussman84
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« Reply #12 on: December 01, 2011, 04:11:04 PM »

Bill, I also went through the roof on our MC-9, our old bus had them just coming out the tank and then pointed down like Ace was talking never had a problem but it was a school bus conversion with lots of ground clearance. So I wasn't sure how it would work on the MCI since there isn't much ground clearance when parked and I didn't want the gas to get "trapped" under the bus where it might cause a stink sitting outside. I used 1.25 black ABS pipe through the roof cut a pretty snug hole everywhere the pipe went through the bus then siliconed around the pipe at each location and used a vent cap similar to what Dr.Steve posted the picture of, only I got the Galvinized metal ones from a local RV supply store about $5 bucks a piece one for the Black and one for the Gray, and used the RV strip caulk to seal where the cap screwed to the roof. So far so good, Hope this helps.

            Billy
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« Reply #13 on: December 01, 2011, 04:42:21 PM »

well if you forget to dump the black tank,  AND YOU WILL someday. of the pipe comes out the bottom so does the overflo. where do you think the overflo goes if its roof vented...........  Just a thought, I have seen soap suds pouring out the top of RVs when they forgot to open the grey valve before doing laundry.  Our vent,    out the bottom this coach and the last
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« Reply #14 on: December 01, 2011, 05:46:57 PM »

not the sharpest tac in the box...but without a p-trap or s-trap doesn't
it make sense that every time you get off the library stool (whether you like it or not) you are venting your black tank ?
And if you have a weepy seal then the black tank is continually venting....
And correct me if I am wrong but methane alone is harmless....unless of course you are suicidal or homicidal.... Undecided
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Red Rider
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« Reply #15 on: December 01, 2011, 05:58:37 PM »

FWIW: I simply follow the plumbing code (UPC) and used a 1 1/2" ABS vertical pipe extending through the roof. I sealed it as Melbo stated with the rubber to the exterior. I took it upon myself to screw a ABS tee ( painted to match the finish) and mounted it facing front to rear. 6000 miles this past summer and no problems.
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Scott Bennett
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« Reply #16 on: December 01, 2011, 06:23:49 PM »

Another vote for the "through the floor" vent pipe. Works great, one less leak potential on the roof...and no issues whatsoever.
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Scott & Heather
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« Reply #17 on: December 01, 2011, 06:34:54 PM »

Not that it matters, but venting underneath is a violation of the NFPA 1192 RV code. At the very least people should know that there is a code--the enforcement is up to the guy doing the conversion. Personally, I don't care how someone vents their sewage tank. Just saying.
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« Reply #18 on: December 01, 2011, 06:40:01 PM »

Out the bottom is not a vent just a overflow all seated coaches rest room equipped are power vented with a fan Prevost has a sealed SS tank with a vent fan and they stink lol  

good luck
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« Reply #19 on: December 01, 2011, 06:41:00 PM »

I have had mine vented out the bottom for 3 years.  2 - 2" inch vents on opposite sides of the tank.  No issues so far. Just sayin..

Although I did leave provisions to vent through the roof if I find myself inclined.
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Brandon Stewart - Martinez, GA
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« Reply #20 on: December 01, 2011, 07:56:54 PM »

Eagle 19952, of course we are suicidal and homicidal==  WERE BUS NUTS
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« Reply #21 on: December 01, 2011, 08:49:02 PM »

Well, everyone knows that codes are merely handy suggestions.  This reminds me of a guy that wanted an easy way to connect his RV generator to his house in an emergency.  He made his own connection cord with male plugs on both sides.  He said it worked fine.  Nothing could go wrong with that, right?

To be honest, if I were building new, that vent would go out the roof.  However, depending on the complexity in a retrofit, I might cheat.
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« Reply #22 on: December 02, 2011, 06:46:49 AM »

I like to use Dicor Lap Sealant when i want to make sure something isn't going to leak.  Grin
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« Reply #23 on: December 02, 2011, 08:53:52 AM »

I like to use Dicor Lap Sealant when i want to make sure something isn't going to leak.  Grin

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« Reply #24 on: December 02, 2011, 04:25:13 PM »

Long ago, a busnut said they used the fitting that goes in the bottom of the kitchen sink as their roof sealing/penetrating device.

Doesn't stick up above the roof and hooks right up to regular plumbing fittings underneath.

Since we all enjoy leak free sink drains in our kitchens without another thought...
pretty neat idea?

happy coaching!
buswarrior
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« Reply #25 on: December 02, 2011, 04:48:46 PM »

I repair leaks under kitchen sinks every week.  A sink basket strainer assembly is not typically designed for a flexible install or any type of movement.

I would stick with something designed for a roof installation that is flexible.

BUT we are busnuts and we get a chance to do it anyway we want and then do it again and then do it again and -------------

Some things I have done LOTS and LOTS of times.

Just my way.

HTH

YMMV

Melbo
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« Reply #26 on: December 04, 2011, 10:16:50 AM »

if I were to run it through the roof, I would use some sort of clamshell type fitting that squeezes on both the inside and outside of the roof and use eternabond double sided to seal it. I've used hundreds of dollars of the stuff...and it's amazing.
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