couple of plumbing questions

[viento1]

Hi guys,

I purchased one of those instant hot water heaters from ebay and have not installed it yet. From what I understand they work quite well, no power draw, no ugly hole in side of bus.

As far as the code goes... I am probably one of those guys who should get the book - oops!

[Sean]

Why would methane build up in a bottom vented tank any more than in a top vented one as long as the vent is open?

Methane gas is lighter than air.  In a proper always-rising vent, the methane rises out the top of the vent and continues rising, dissipating in free air.

If you loop the vent line so that it goes down, the methane will rise to the top of the loop and remain there, which is, itself, a hazard.

Furthermore, when enough gas emits from the tank to finally push the methane out the bottom vent, the methane will be below the coach, and it will rise through any openings right back into the bus.  Depending on air currents, etc, it could rise right into a compartment with spark-producing equipment and cause an explosion.

Lastly, whether it is methane or anything else, most sewer gases rise, so when they finally get pushed out the bottom vent, they will rise into the coach, where they can make someone ill or worse.  Gases will also tend to build up in the tank without a continuously rising vent, and, ff you have a trapless RV toilet (which is most of them), some of that gas will rise back into the coach when the flush gate opens.

If the vent is plugged there is no difference.

Plugged vents are a problem.  If you do not use your rig daily, I recommend inspecting the vents before every trip.  This is a poor justification for doing the venting unsafely and in contravention of accepted codes and standards.

Does this code book apply to bus private bus conversions?

Depends on the state.  Not all states have adopted all parts of this code.  I don't have a list, but if you Google the code on government sites, you can get a general idea of just how widely accepted this code is:
http://www.google.com/search?q=nfpa+1192+site%3A.gov

(Note that many states, counties, and municipalities do not have ".gov" domain addresses, so this search is extremely incomplete -- it's just to give you a sense.)

But why would you want to do something unsafely just because the state you happen to be in is lax about this sort of code enforcement?  I can assure you that they are not as lax when it comes to vents in fixed structures -- vents must always rise continuously to the outdoors.  It's only because privately built RVs are such a tiny fraction of their overall jurisdiction that they pay little attention -- they know that manufactured RVs are already built to this code.

If a waste tank overflows where does the excess go?

It is unlawful in all 50 states for your black waste tank to overflow.  Some states are more lenient about gray waste.

As has already been written, if you overfill the black tank, it will back up into the toilet.  If you overflow the gray tank, it will back up into the shower pan.

This is one reason I recommend against combined tanks, BTW -- in a combined tank system, when the tank overflows, raw sewage including black waste can back up into the shower pan.  Yuck.  (The other reason is that if your P-traps happen to empty, due, say, to driving conditions, then sewer gas from the black tank can back up into the rig.  Even if you have separate tanks, I recommend priming all your traps whenever you stop and get leveled.)

-Sean
http://ourodyssey.blogspot.com

[gus]

If Methane is present it makes pressure so it is always flowing from the vent, even the slightest pressure will push it our a bottom vent. The pressure won't build up and suddenly push accumulated gas out the vent.

I have never smelled any gas from my vent, even the slightest breeze will dissipate the gas so the chance of it ever being concentrated is nil.

My toilet flows to the bottom of the tank, no methane comes out my toilet.

Do you inspect your rooftop vent before every trip?

So far I haven't seen or read anything that says a bottom vent is unsafe. If I thought it was unsafe I wouldn't do it.

There are a number of other busnuts with bottom drains and none of them have ever posted about any problems.

Vents in fixed structures are there primarily to prevent a vacumn in the drain system, not to release gas. These vents actually take in air rather than vent it out. Traps keep out the gas.

[Sean]

If Methane is present it makes pressure so it is always flowing from the vent, even the slightest pressure will push it our a bottom vent.

That's not correct.  Methane can sit in the top of a loop of pipe for hours.  It does not "make pressure" -- only the generation of additional gas inside the tank will create additional pressure.

The pressure won't build up and suddenly push accumulated gas out the vent.

I did not say it would.  I only said that when additional gas is produced, the methane would be pushed out the bottom and then immediately begin to rise, possibly back into the coach.

I have never smelled any gas from my vent, even the slightest breeze will dissipate the gas so the chance of it ever being concentrated is nil.

My toilet flows to the bottom of the tank, no methane comes out my toilet.

So far I haven't seen or read anything that says a bottom vent is unsafe. If I thought it was unsafe I wouldn't do it.

There are a number of other busnuts with bottom drains and none of them have ever posted about any problems.

All four of those statements represent a common logical flaw -- since I've never had a problem, and other people I know have never had a problem, and we've been doing it this way for a long time, it must be safe.  The problem with that reasoning is that many things are safe, and cause no problems,  99% or 99.9% or even 99.999% of the time.  Yet history is full of tragic tales of problems that could have been avoided had people just known what could happen, even though some things don't happen often.  Codes are created for exactly this reason.

Do you inspect your rooftop vent before every trip?

I don't go on trips, I live in my bus full time, so there is no opportunity for nests to get built, etc..  But that's not really germane to the discussion, now, is it?  We weren't talking about routine inspections, we were talking about design and construction standards.  I suspect many people don't inspect their running lights every day (although I do), either, but that does not relieve the coach builder of the obligation to install them.

Vents in fixed structures are there primarily to prevent a vacumn in the drain system, not to release gas. These vents actually take in air rather than vent it out. Traps keep out the gas.

This, too, is incorrect.  If vents only needed to admit air to prevent vacuum, there would be no need to run them to the roof (as is required by the Uniform Plumbing Code), and every fixture could just have an AAV on it.  All waste lines are required to be vented to the outside in order to vent sewer gases.  Try venting your sewer line into your living room for a while, and I am sure you will soon notice that, indeed, sewer gas comes out.

Proper traps keep gas from flowing back out of the stack and into the structure through the fixture drain.  But each time a fixture drains, gases in the waste lines are displaced, and those gases have to have some place to go.  That place is up and out the vent stack.

Code (both the RV kind and the UPC) even dictates the size of vent lines and stacks all the way to the roof.

Lastly, I have already pointed out the exact code requirement in black and white.  So it is indisputably the law, at least in most jurisdictions.  And I can assure you that the equivalent requirement in the UPC for fixed structures actually is the law in every jurisdiction in the US.

And now, you can no longer say that you have never read anything saying a bottom vent is potentially unsafe -- you just read it right here.

-Sean
http://ourodyssey.blogspot.com

[bevans6]

I'm the OP, and want to thank everyone, especially Sean, for the  discussion.  Really confirming things I already knew, at least from a house point of view, but wanted to double check.  My black tank is currently vented into the top of the rear axle compartment, which forms the floor of the bedroom, said floor is probably not proof  to incursion from sewer/methane gasses.  At least it was vented somewhere...

Today's job is to start to re-plumb the coach, fixing issues (like that one, and having the water pump installed  by dangling it from it's lines in mid air), start to plan for cutting the fridge side access panel, and a few other things.  Even if I have to fix a few things, it's a whole lot easier than starting a conversion from scratch!

Brian

[Blacksheep]

I have been reading this and as always Sean is a walking bag of knowledge or at least knows where the answers to code questions are, but what I did was to go out to my bus which still has the original holding tank and I'm still looking for the vent. How did a commercial transport bus get built, run and carry upwards of 40 people at a time without a vent going thru the roof? I'm sure Prevost not to mention all other transporters were built unsafe to carry these people! So if their vent didn't go thru the roof so the methane gases could go upward into the atmosphere, then just where did it go? Is there another means of venting the large SS "combined" holding tank that is oem on mine and I'm sure other buses?
Just curious!

Ace

[Dallas]

Ace,
I'm not sure about your H3, but the Prevost's that we saw in Ohio had a 3/4" or 1" hose running from the factory lavatory waste tank up to the vent on the back of the bus where the cap comes down.
I think the reasoning was that since these weren't motorhomes, but used mainly for the transport of passengers, the only regulations they needed to follow were DOT and NTSB.
I've seen the same typr of vent hose on MCI and Setra and VanHools.

YMMV

Dallas
(Smoke - Groan) 

[skolbibp]

If you're cutting holes in the baggage door panels IBP may be able to supply panels with vents so it will look more like the factory style panels.  If you have any questions please don't hesitate to call me at 1-800-468-5287 x232

Thanks
Steve

[Blacksheep]

Dallas I have looked and looked with out finding any type of vent in or around the cap area or any type of hose! Besides if they used a hose that small would it be sufficient? Everyone is saying it should be 2 inches!

Ace (not smoking OR groaning YET) 

[Sean]

... Sean is a walking bag of knowledge ...

Interesting choice of words, Ace...

... my bus which still has the original holding tank and I'm still looking for the vent. How did a commercial transport bus get built, run and carry upwards of 40 people at a time without a vent going thru the roof? ... So if their vent didn't go thru the roof so the methane gases could go upward into the atmosphere, then just where did it go? Is there another means of venting the large SS "combined" holding tank that is oem on mine and I'm sure other buses?

As Dallas wrote, there should be a vent hose leading up from the tank if you hunt around.

That said, this type of toilet is very different from an RV model.  Many have no trap or flapper, and so the tank is open to the inside of the coach at all times, with only possibly the toilet seat in the way.  This type of toilet system must have a fairly strong chemical additive in it, one function of which is to break down the waste chemically, rather than bacteriologically.  One of the safety issues with inadequate venting is the possibility of airborne pathogens entering the living space, and this, too, is mitigated by the strong chemical disinfectant.  Another key difference with passenger coaches is that, typically, waste does not remain in the tank even overnight -- most motor coach restrooms are emptied at the end of every day.

Lastly, in general, a passenger motor coach does not constitute a living accommodation, so the safety issues are different.  For example, food preparation is usually not done, nor are all the occupants generally sleeping on board.

All of that said, I don't know about you, but I would not want a bus-type toilet for my house.  In part, that's because the venting is really not adequate for the purpose, as anyone constrained to spend an entire bus ride in row 14 can attest.

-Sean
http://ourodyssey.blogspot.com

[Blacksheep]

Sean the bag word just came out as habit and not meant to be disrespectful. You know like bag of bones, Ole bag, etc! all in fun!

With that said, back to the vent!

You said that all buses are usually emptied every night! Hmm, when camping with full hook ups, in a livable bus, the waste tank is merely a pass thru with nothing much if anything at all staying in the tank!

Also you said that buses must have a very strong chemical additive to help break down the waste. How many times have we read here that additives are not needed or good for that matter? Why would bus companies do this IF it's not a good idea?

As always I am probably a little confused as to the contradicting reports here such as flapper, no flapper, large vent, small vent, Vent up, vent down, additives, no additives, smell, no smell!

All in all, a toilet is a toilet. It does one thing. Gives you a place to deposit your waste. I can't imagine a BUS toilet not having some sort of seal such as a flapper or valve other than the toilet seat to seal off what odors etc. may rise upward from the holding tank! Also why don't bus builders that build buses for transporting people, have separate holding tanks for gray and black? Mine was a combined tank! Another thing I was told was the wrong way to go!

Bottom line is, if it (the tank, toilet, vent was good enough to have in a bus to transport 40 plus people and approved for use, why wouldn't a similar set-up work for a couple 2-3-4 people on a camping trip?  I mean they will probably let it all out once they hook up to the camp sewer! I ALWAYS drain my tank either before I leave for home or while I am camped! How can this be unsafe?

My 2 inch vent goes downward thru the floor of the bay and rearward. I have YET to see, smell or have any type waste problems with this set-up! Notice I didn't say YET? I don't see any problems arising anytime with the way my system is designed! I would really hate to see anyone put un-necessary holes in a roof of a bus if they didn't have to!

Sorry but sometimes, as I have said many times before, people need to look OUTSIDE the box! I agree codes are written for various reasons but even the game checkers has rules that are supposed to be followed but very often they are challenged with the two playing parties! The point is, not everyone follows the rules and I doubt very seriously that someone will have their bus blow to smitherines because they vented down instead of up!

Again... just my opinion!

[Dan C]

The original toilet on my bus, 1990 102A3, was as Sean described an "out-house". Just a toilet seat covering the 9" diameter hole to the tank. These tanks were dumped every day, but the real reason that the oder did not enter the coach is that the tank was vented the the air cleaner and the the engine ran all day. As long as the engine "sucked" on the tank there were no oders. This was not the case when I first used the coach on a 4 day run and shut the engine off when not driving. Household bleach came to the rescue. Many people asked me why we all remove the original toilet. I tell them that "I did not want an 'Out-House'" in my moterhome.
Dan

[Sean]

You said that all buses are usually emptied every night! Hmm, when camping with full hook ups, in a livable bus, the waste tank is merely a pass thru with nothing much if anything at all staying in the tank!

If you always have full hookups, then there is no need for a tank at all.  The rules and best practices are formulated based on the idea that an RV is self-contained and can, theoretically, be used for a period of several days without hookups.  As such, they need to be set up properly for this usage.  Moreover, as I am sure you know, a sewer connection is the least common type of hookup -- many, many parks providing electricity and water do not provide sewer, or sewer is provided only in certain premium spaces, and, instead, the park has a dump station.  I would say that 97% or so of the times we have had electricity available, there has been no sewer hookup.

As a separate note, I will point out that even if you always choose a site with sewer, generally you should not leave your black valve (or combined valve if so equipped) open.  You should keep the valve closed until the tank is at least a quarter full or so, and re-close the valve after dumping.  This is to prevent the build-up of solids in the tank.  So even with full hookups, a proper vent is still required.

Also you said that buses must have a very strong chemical additive to help break down the waste. How many times have we read here that additives are not needed or good for that matter? Why would bus companies do this IF it's not a good idea?

You are comparing apples and oranges -- RV toilets and bus toilets are very different.  Bus sanitation systems are required to use chemical disinfectant (and note that this is different from deodorizer, which is often the only thing RV tank additives contain).  I am talking, here, about a standard coach restroom, not a bathroom in any kind of conversion, to include entertainers or executive coaches, which usually have RV-style bathrooms.

... I can't imagine a BUS toilet not having some sort of seal such as a flapper or valve other than the toilet seat to seal off what odors etc. may rise upward from the holding tank! ...

Then I submit you have not used the restroom on very many passenger buses.  I try to stay out of them myself, but that didn't stop me and most of the other ~40 people on a 96A3 from coming down with a norovirus en route from Prudhoe Bay to Fairbanks.  Many were hospitalized, and my wife and I spent two days of misery in a Fairbanks hotel.

Bottom line is, if it (the tank, toilet, vent was good enough to have in a bus to transport 40 plus people and approved for use, why wouldn't a similar set-up work for a couple 2-3-4 people on a camping trip?  I mean they will probably let it all out once they hook up to the camp sewer! I ALWAYS drain my tank either before I leave for home or while I am camped! How can this be unsafe?

Again, the designer or builder of an RV can not assume that tanks are drained frequently.  Nor can the "good enough for a passenger bus" reasoning be applied to something which is not a passenger bus -- they don't have seatbelts either, but many states require them at all "travel" seating positions in an RV.  Declaring your Prevost to be an RV exempts you from many rules you would be subject to if it were a bus, such as having a class-B CDL with air brake (and passenger, as applicable) endorsement, keeping an hours-of-service log, and stopping at scales and inspection stations.  And it subjects you to other rules, such as NFPA-1192, that are not applicable to passenger buses.  You can't cherry-pick just the rules you like from both categories.

My 2 inch vent goes downward thru the floor of the bay and rearward. I have YET to see, smell or have any type waste problems with this set-up! Notice I didn't say YET? I don't see any problems arising anytime with the way my system is designed! I would really hate to see anyone put un-necessary holes in a roof of a bus if they didn't have to!

Not wanting to put a 1.5" hole in the roof is, IMO, a poor reason for failing to follow safe, accepted, and compliant practice in the industry.

It is extremely unlikely that any problem will arise from a downward vent.  However, I will point out that it is extremely unlikely that an airplane will crash-land in the ocean, and even less likely that anyone would survive the event, less likely still that any survivors will make it out of the airframe alive and safely.  Probably all of these things are less likely than someone getting sick from sewer gas in an RV.  Yet still we require airlines to carry life rafts -- for something that will probably never happen.  Now ask the folks who survived the ditching of Cactus 1549 if they were glad such a regulation existed.

As I have said here many, many times, these rules, which constantly evolve over time, do not really exist to prevent problems that are common or could be commonly anticipated by the average person.  They exist to prevent generally unlikely problems that have demonstrably happened in the past to someone's detriment.  I will further tell you that such rules usually do not get codified until many such problems have occurred.

Sorry but sometimes, as I have said many times before, people need to look OUTSIDE the box! ... The point is, not everyone follows the rules and I doubt very seriously that someone will have their bus blow to smitherines because they vented down instead of up!

So, what you are saying is that the rules don't apply to you, or maybe to bus nuts in general, and we should all be free to do things however we wish, so long as we personally believe it is safe.  While that is a lofty ideal and might work if absolutely everyone who built anything had the technical chops to do it right and safely every time, history has proven otherwise, and society long ago decided collectively not to allow this.  Just try to build a house in any municipality in this country without following the rules, and see how far you get.  Or perhaps something closer to home -- try to make a race car without following any rules, then show up at the track without proper safety equipment, and see if they let you race.  The line has to be drawn somewhere, and in the field of constructing living accommodations, whether those are mobile or not, those lines are very clear.

No one follows every rule, not even me (gasp).  But I maintain that it is irresponsible for anyone to come here and deliberately advise people to do otherwise -- especially if those people being so advised are already unsure enough of how to do things correctly and safely that they are asking questions here.

If you are starting from scratch, following the accepted practices adds only minimal expense and inconvenience -- why would you want to risk anything at all to save a few dollars?

-Sean
http://ourodyssey.blogspot.com

[Len Silva]

As it stands today, the powers that be are quite lenient with us.  No special license or test to drive a twenty ton bus, the insurance companies don't look too close at what we build, or what codes were followed.

If there were to be a rash of accidents and/or lawsuits with bus conversions and anyone ever put two and two together, you can bet that would (and probably will) change.

It behooves all of us to use due care and diligence in designing and building our coaches.  Fortunately, most folks on these forums do care. Unfortunately, there are many out there that do not belong to our groups, nor do they care.

Len

[Blacksheep]

First of all nobody came here at least I didn't and insinuate that I didn't care how things were done! I think people should take notice on what's done right or wrong and especially if its a safety issue! As Sean stated, very unlikely a downward vent will cause major problems and in telling someone that it CAN be done because it HAS been done is not advising someone to do something that will harm them!
What I truly think is that rather than worry whether your vent goes in the proper direction, some people should take a really close look at what THEY are driving on the road! How many buses have you seen at a rally up close and personal and ask yourself how in the heck did it make the trip? Now that is something people should look at! Tires, brakes,major oil spots from leaks on the engine, air leaks that are clamped with vice grips, broken windshields, doors that don't close and lights litterally hanging off the bus yet they still drive them on yours and my roads. You get my point I'm sure! What's more important? A safe ride or a toilet vent?
I'm not saying the codes are a bad thing and everyone should follow them to a T. Heck even our resident code meister admits to not following the rules entirely so what makes you think everyone else has or will for that matter?
Even noobs are going to see on other conversions that there are other SAFE ways of doing things that actually work.
So you can preach until the cows come home. Your not going to convince NOOBS or OLDS to follow the book!

Ace