tank vent help needed

[crown]

 sean does it mater if its rear or front of a/c i need to cut holes in roof looked on e bay for moterhome
roofs looks like there not 3 ft away not saying it corect just looking for all the imfo i can get before
cutting roof posting a picture

[Sean]

sean does it mater if its rear or front of a/c i need to cut holes in roof looked on e bay for moterhome
roofs looks like there not 3 ft away not saying it corect just looking for all the imfo i can get before
cutting roof posting a picture

Well, as I implied earlier, whether or not a roof air is considered a "motor-driven air intake" is open to interpretation.  Clearly, several RV manufacturers have interpreted that it is not, and I myself presumed that when I designed my coach (based on Dometic Penguin specs and the fact that many factory RVs had roof airs closer than 3' to the vents).  I later regretted that interpretation, because enough air is brought in by that unit to be a real problem when I flush the toilet.

Now, I have a bigger issue than most folks because of the air flush (every flush pushes 8-10 liters of air out of the tank through the vent).  But still, I think it could be a problem even with conventional toilets.

What I am saying is that you may get away with it under the code, but my advice is to keep the tank vent as far from any roof air as possible anyway, unless you want sewer gas in the rig.

I have very, very few regrets about design issues on my coach, and this is one of them.  FWIW.

-Sean
http://OurOdyssey.BlogSpot.com

[crown]

 sean what type of tolit do you have i am using a microphor tolit

[Nellie Wilson]

Geez, Louise!

Whatta bunch'a blarney. This ain't exactly rocket science, now is it? Let's see... holding tank. Hmmm.. air pressure and bad smells. One prevents good operation, the other prevents peaceful domicile.

Solution? A hole, preferably with pipe attached, venting into less pressure.  Kill two birds - pressure and stink - with one hole (sorry for the mixed mataphor  ).

Yeah, I know I'm gonna get flamed. Too simplistic, too 'female,' too 'not in keeping with some code' that nobody follows anyway.

To my point: Crown, just run a U- shaped pipe out the top of your holding tank and through your bin (luggage bay) floor. Save yourself tons of time and $$ and frustration. Better yet, use a piece of garden hose and some hose clamps to test it out. Doesn't work, nothing lost... but , guaranteed, it will work.

Nellie  Wilson.

[Sean]

sean what type of tolit do you have i am using a microphor tolit

We have a Microphor LF-210 air flush model.  Our waste tank is too far from the commode for a standard direct-drop unit.

... just run a U- shaped pipe out the top of your holding tank and through your bin (luggage bay) floor. Save yourself tons of time and $$ and frustration. Better yet, use a piece of garden hose and some hose clamps to test it out. Doesn't work, nothing lost... 

Unless it explodes.

Folks, there's a reason why vents MUST slope upwards at all times and exit through the roof.  This is true in houses as well as RV's.  Sure, you might get away with it indefinitely and never have a problem.  But the next guy might die from it.

I don't want to rehash this whole debate in this thread -- probably everything that can be said about this has already been said on this board already.  See this thread:
http://www.busconversions.com/bbs/index.php?topic=12131.0

-Sean
http://OurOdyssey.BlogSpot.com

[cody]

While in florida, we went to an rv show in Ft Meyers, I was looking over a brand new TravelSupreme with all the toys, the unit was show priced at a thrifty 500K, down from 650K according to the nice guy that was trying to sell it to me lol, I commented on the quality of the plywood in the drawers and the staples, I remarked that I prefered dovetails, he told me they were dovetail fasteners, I went ohhhhhhhh I see lol.  The vent on that one went from the tank in the back bay straight up to the top of the bay, took a 90 to the rear and into the fender well, then took another 90 and exited the fender well with a small scoop that aimed it to the back, I wonder what code that brand new coach was following.  That was a couple of years ago.

[Nellie Wilson]

Sean -

Not for one second do I doubt your wisdom and authority on this matter - and I sincerely mean that.

However, I am parked within 15' of a bus professionally converted in 1991 - by a well reputed converter - that has both fresh water and holding tanks vented through the bottom. Neither the previous owner - a corporation that used the bus as a mobile 'think tank' (sounds rather appropriate  ) nor the present owner (of some 15 years) has had a problem.

Anecdotal evidence? Yes. Convincing evidence? Also yes.

But buds can disagree, right? Luv ya!

Nellie  

[cody]

My bus was owned by a blues singer before I got it, he had it converted by the Caldwells, they are a very respected professional conversion company,  the black water tank had a straight drop out the bottom thru the bottom of the bay floor, controled by an air switch on the dash lol, the vent also went straight down thru the floor, I've been piling sawdust in buses, motorhomes, travel trailers and all sorts of rvs in between for years, I've seen probably every concievable combination of factory venting including a system years ago that fed the contents of the black and grey tank into the exhaust system that supposedly burned them creating a no dump tank lol.  I realize the codes are there, I also realize that they tend to have a way of getting around them as the engineering needs dictate at times.

[Sean]

However, I am parked within 15' of a bus professionally converted in 1991 - by a well reputed converter - that has both fresh water and holding tanks vented through the the bottom. Neither the previous owner - a corporation that used the bus as a mobile 'think tank' (sounds rather appropriate  ) nor the present owner (of some 15 years) has had a problem.

Anecdotal evidence? Yes. Convincing evidence? Also yes.

Viviane, I can share many horror stories with you of things I, too, have seen in "professionally converted" coaches and even factory RVs that would give you pause to ever consider buying one.  Any home inspector can also share horror stories of unsafe situations they have encountered on the job.

As I have said here many times in the past, just because some otherwise reputable and supposedly professional outfit has done something does not necessarily make it right or safe.  In theory, Toyota, as the largest car manufacturer in the world, ought to know how to make a safe gas pedal, too...

As I have also written many times, including in the thread I referenced above, codes exist, in part, to prevent unsafe situations that may occur in a tiny, tiny fraction of cases.  So anecdotal evidence that a certain way of doing things has not encountered any problems in some known set of observations is not convincing -- it's that .0001% when it doesn't work that gets you.  As I wrote in that thread, the chance that an airplane will crash is minuscule, and that the passengers would survive a crash smaller still, so why, then, do we equip every passenger with a life vest?

At some level, each of us, perhaps without acknowledging it, is relying on adherence to codes by other people constantly.  Would you get on an elevator if you knew that the guys who built it omitted the safety interlocks, or the free-fall brakes?  Or would you get on a ship if it had no life boats, water tight compartments, or life jackets?  Probably not.  Yet you don't crawl into the elevator shaft before every trip to see for yourself if these things were done -- you trust that someone, somewhere, is enforcing compliance to safety standards that you assume exist and have been well thought out to ensure your safety.  In fact, when this system of codes and enforcement breaks down, we even tend to be outraged: Why weren't hospitals in Haiti built to earthquake standards?  Who let those Colgan Air pilots fly that plane on too little sleep, and blithely chat away in the cockpit instead of watching the instruments, and paying attention to stall speed?

We all understand why cars need brakes, or why people are supposed to stop for red traffic lights, and so we understand (and mostly agree with) laws that dictate those things.  Few people understand why bedrooms need arc-fault protectors, water heaters need relief valves, or sewer manhole covers need holes in them.  For the most part, this lack of understanding is not an issue because most people do not wire their own houses, build their own water heaters, or run their own sewer systems.

People who convert their own buses, as a matter of course, are taking on a project that will require them to understand (or hire someone who understands) safe practices, and thus relevant codes, in electrical wiring, fresh water plumbing, drain-waste-vent plumbing, ventilation, heating, refrigeration, and, if applicable, gas line plumbing.  That's a tall order, and a forum such as this one can be a big help, but it is still fundamentally up to you to learn what you need to know to make a safe conversion.

On the matter of vents, the code is crystal clear and not subject to interpretation -- they must extend through the roof.  And the reasons, while less clear to many people, are well-founded and easy to research.  I spelled them out extensively in the other thread.  Advising people that this provision can be safely ignored based on extremely limited personal observation and other anecdotal evidence, while well-intentioned, ultimately does not square with my perception that you are a person genuinely interested in the well-being of those around you.

Most importantly, I would not want to see you (or anyone else) injured or made ill by an improperly vented system, which is why I also made a firm recommendation about your own vent situation in the refrigerator thread.  Hey, you're my bud, right?

-Sean
http://OurOdyssey.BlogSpot.com

[NewbeeMC9]

From someone who bought a previously converted bus,    While you are converting it,  take the time and effort to put the plumbing vents away from and downstream of your Roof vents and A/C.  and also put vents on the drain pipes.

I will say this is my first RV  of any kind so it is quite the learning experience.  If you're going down the highway at a pretty good clip and the ceiling vent is open even the slightest and someone flushes the potty, there is where you will wish you had put the extra effort into excellent venting .


My toilet is the Sealand ball valve type with the strait drop into the tank.  I don't know what others have.  If the tank were vented thru the bottom of the bus, then the potty would be the highest point, and the inside of the bus, therefore any gas that rises will vent inside the bus.   IIRC methane is odorless(gas company adds that smell) and I believe it may rise in air.  Either way, any gas rising out of the black tank is not welcome in the bus

There many ways to vent and some work somewhat and some is better than none (unless it is venting strait to the bay. )  but that doesn't make them it a particularly good idea.


If I ever convert or reconvert.  I would plan the vents, according to code since we know it. (remember code is a minimum requirement) and I would  have two vents on the tanks through the roof most likely and possibly an overflow through the bottom also, for chimney effect flow. Remember air(gas) needs a full path to flow.  I do not want the toilet to be a vent again   And I would try to make them away from and behind the roof airs now Sean .  The pipe drain vent through the roof could possibly work as one of the vents.


Just my opinion from experiencing what not to do.



Since my bus IS converted, what about these spring vent things you speak of??   Any info, pictures?

[PCC]

The AutoVent is available at any hardware store. Usually attaches with a 1 1/4" plastic connector. One such unit is onthis webpage: http://www.plumbingsupply.com/autovent.html

These can save the need to run every line out the roof, BUT, and I hope I never implied this, there MUST be at least one vent line from the drain system to the outside (to get rid of the gas vapors).

If not, the gasses will collect in the pipes, and that could make you think twice about lighting up.

[crown]

 ok lots of stuff to think about i am going up and out roof just not sure where yet i did come
up with a fix for the round roof jaccuzis use flex hose that uses standerd pvc pipe fittings
and glue so that will make the bend easy  sean my microphor is almost a direct drop to tank
can you tell me more about them i picked mine up at marathon coach one lucky day they
were cleaning up warehouse and this one had no tank lid bought it for $ 20.00 picked up the
next day and thay found the lid packed away and gave it to me thats all i known about them
thanks

[cody]

In this case I will agree that Sean is correct in the code and application of it, this code is often varied to a certain extent tho as we have all seen by factories and converters, I will give the floor to Sean in this code tho like I said, however, I have found many times that our resident code expert to be batting approximately 60% in the accuracy of codes and applications of them, this however, is a far better batting average than most of us have, what I'm saying is that it's important for all of us to research the codes ourselves, far too often we take information for granted as being gospel only to find out later that it has been replaced by a new code or adjusted to correct some new found flaw, so don't rely on what you read on the internet, do the research, buy the books and read them.

[Sean]

...  sean my microphor is almost a direct drop to tank
can you tell me more about them ...

Microphor makes many different models, including macerating toilets for marine use and self-contained models for railroad locomotives.

I have the type that uses compressed air to send the waste to the tank via a 1.5" waste line. It sounds like you have the type that uses a direct drop below a standard flap valve and requires a 3" connection.  This type is available in manual or electric flush.

The model number should be on a sticker inside the "tank" area.  If it's missing, you might have to go through several manuals to figure out which one you have.  But then all the installation and service manuals are available on Microphor's web site:
http://www.microphor.com/html/downloads.html

[AAVs] can save the need to run every line out the roof, BUT, and I hope I never implied this, there MUST be at least one vent line from the drain system to the outside (to get rid of the gas vapors).

Just to be clear about this, AAVs are permitted as secondary vents.  Each and every drain must still be vented outside.  The AAV is used to provide the required anti-siphon air admittance within the maximum 6" distance from the trap.  This allows the actual vent to be further away.  This type of installation is the only way to implement, for example, an island sink installation.

... I will give the floor to Sean in this code tho like I said, however, I have found many times that our resident code expert to be batting approximately 60% in the accuracy of codes and applications of them,

Sheesh, Dan, I've made two or three mistakes in several hundred posts, and you're only giving me a 60?

FWIW, even code inspectors make mistakes -- I've sent more than one back to his code book.  These codes are voluminous, no one can possibly memorize all of them, and it's common for us to misremember something that is in one section as being in another.  Also, most codes are updated every three years.

This is why I try to look up each and every provision on the spot when I post here.

FWIW, my 1192 is two revs out of date (I have the 2002, and the current version is 2008), and I can't justify buying the latest version just to answer questions here.  The mistake I made recently in another thread (http://www.busconversions.com/bbs/index.php?topic=14724.msg157584#msg157584) was the result of relying on someone else's (bad) information about a change to the code, along with having provisions from the ABYC standards swimming around in my head, which are not relevant here but similar enough to be confusing. (The solenoid we were discussing is mandatory in the ABYC standard, optional in the RV code.)

I did cave in and bought the 2008 NEC when I started teaching coach electric systems (I used the 1999 code when I designed my bus), and so all my posts on electrical systems are based on actual reference to the latest code.  And now I've discovered that I have limited access to the 2008 RV code as well.  When I find I have made a mistake, I always go back and correct it.

-Sean
http://OurOdyssey.BlogSpot.com

[cody]

All I'm saying, is that even the most knowlegeable among us can be wrong, don't just take what a person reads on the internet as the final word, hey any sports hero that batted 600% would be fought over by any team, right? lol  I even remember once that I thought maybe I had made a mistake in a refinishing article, but I was wrong lol.