couple of plumbing questions

[Len Silva]

Ace,
I agree completely.  It's scary when someone asks electrical stuff because they have no idea how it should be done.  It's a whole lot scarier when they ask those questions about brakes. ....Oh, brakes need to be adjusted, I didn't know that!

I've seen some charter and entertainer buses that I wouldn't ride on.

Now, as to our buses, I can get worked up about electrical and propane. Frankly, I don't much care how someone else does their sewer vent.  It is highly unlikely that it will impact me, and if it does, I can move.

A hot skin or fire on the bus parked next to me is a concern.

I'm an OLD and I'm convinced.

[Blacksheep]

Len I'm in agreement with you too but we sort of swayed from the plumbing issue!

My point was, there are a whole lot more important things on a bus to worry about than following a code for a vent tube!

Ace

[Sean]

My point was, there are a whole lot more important things on a bus to worry about than following a code for a vent tube!

Ace, I agree with this completely.  I'm not trying to make a mountain out of a molehill, I'm just responding to the arguments that there is no reason for the concern -- if there were really no reason for it, it would not be in the code.  And, frankly, some of the counterarguments advanced have just been plain wrong, and I think people who come here for information and learning deserve to hear the facts, not speculation.

If someone came to me for advice with an existing bus that was not properly vented, I would inspect it and make an informed guess about whether or not it was a big enough concern to warrant tearing things out to fix it.  I would not blindly say it has to be changed (although a code inspector might do just that).  I can probably even say the same thing about some electrical concerns.  But if people are starting from scratch with an empty shell, there is really no excuse for not doing it correctly from the beginning.

-Sean
http://OurOdyssey.BlogSpot.com

[kyle4501]

But if people are starting from scratch with an empty shell, there is really no excuse for not doing it correctly from the beginning.

-Sean
http://OurOdyssey.BlogSpot.com

If some one is wanting to convert a bus, it is better if they understand the system they are installing BEFORE the installation. Once they know the preferred way, they are better able to make an informed decision as to what 'their way' is.


Ignorance can be cured, but there ain't no fixing stupid. 

[gus]

We're talking two kinds of vents here, drain vents and waste tank vents.

I repeat, the primary purpose of a building drain vent is to take air in, not vent methane. Traps keep methane out of a building. The reason vents go through the roof is because they must be kept higher than the highest drain, not because they vent methane. This is a common myth and may even be believed by some plumbers.

Drain vents in an RV serve the same purpose, without them the traps would be sucked dry every time water went down the drain system. These vents could go out the side of the RV if desired since they take air in, not out. Check valves can also be used which take air from inside the bus and avoid more roof holes and long vent pipes. I use these valves.

A waste tank vent is slightly different but not much. This vent allows sewer gas to evacuate as the tank is filled with liquid and allows fresh air to enter when the tank is emptied. Without this vent the tank would bulge when filling and collapse when being emptied.

The reason for large building roof vent pipes is that the vents are so long and the drain pipes so large that a small vent pipe would not allow enough air to enter the drain pipe as the liquid flowed out. My bottom vent pipe is only 1.25" and perfectly adequate because it is so short.

Any pressure of any kind in a waste tank will evacuate methane if it is present, including incoming liquid. The theory that it will accumulate in the loop is just a theory, nothing more. The theory that there is enough methane in an RV waste tank to be hazardous is also just theory, nothing more.

If anaerobic bacteria is allowed to grow in an RV waste tank there won't be any significant methane, or solid waste for that matter. The problem is that most RVers seem to insist on cleaning the waste tank at every dumping or adding strong chemicals. Bad. This kills the little ab who will do the job much better if only allowed to live. I never completely empty my waste tank.

There is nothing to indicate that methane in an RV waste tank is a problem. I've never heard of an RV explosion caused by methane?? I've also never heard of a methane explosion in a home for that matter. Just because it is posted here that it is a danger doesn't make it so. These are opinions.

Saying that a bottom vent is incorrect or unsafe is baseless. Saying it is doesn't make it so. I'm always amazed when a poster says another poster is wrong with no base for such a statement. Disagreeing is one thing, saying another poster is wrong is another thing altogether and not necessary. I was under the impression that we post here for the information of the questioner and that it was up to him to decide what is right and what is wrong?

Codes are very often more political than technical or safety based. Copper vs PB water supply pipes is the best example I can think of. PB is superior in every way to Cu yet it is not approved in many location. Why? Because it protects the Cu suppliers.

One can make a choice, blindly follow mindless codes or think! It is easy to follow mindless rules and regulations but a bit more challenging to think.

If I thought for a minute that my bottom waste tank vent or my long toilet drain pipe were safety hazards I would change them but so far there has been nothing reliable posted to indicate that. My ole Grandpappy told me long ago to beware of experts and engineers!!

[MCI-RICK]

Hello everyone!

I've really enjoyed following the discussion.  I never thought a post on waste and venting could be so captivating.  There's always something that you can walk away with if you looking.  I now know to close the dump valve after the tank is empty when I'm staying hooked up.  I don't think anyone mentioned that doing this would also prevent sewage odors from rising into your bus from the massive tank below ground.  I know those odors rise when you uncover that tank from experience.  If you dare to stand directly over the tank when you uncover it to hook up, prepare to receive the perfume of all those that came before you.  I'm a newbie with buses but I've been RVing for years and have experienced that unforgettable aroma on several occasions. 

I'll remember to keep my black and gray tanks vented separately.  Thanks everyone!   

Rick   

[sweeney153]

There is nothing to indicate that methane in an RV waste tank is a problem. I've never heard of an RV explosion caused by methane?? I've also never heard of a methane explosion in a home for that matter. Just because it is posted here that it is a danger doesn't make it so. These are opinions.

I did a google search. the first thing to come up
Debris from the Makati mall explosion last Friday that left 11 people killed, 112 wounded and three others missing show signs of a possible methane gas explosion,
http://www.gmanews.tv/story/65439/Blast-site-shows-signs-of-methane-explosion

Then i searched youtube
Methane house explosion
http://www.youtube.com/watch?v=U5vbcG1lwiQ


Its Not a myth

 Methane explodes

[Sean]

We're talking two kinds of vents here, drain vents and waste tank vents.

In most RVs, my conversion included, these are one and the same.  Sure, you could have separate tank and fixture vents, but why run the extra pipe or cut another hole in the roof?  For that matter, for most RVs, wet-vented systems are permitted (there are limits on the number of fixtures, and size limits), unlike in most fixed construction.  So careful design lets you get by with a single stack for both waste and vent.

I repeat, the primary purpose of a building drain vent is to take air in, not vent methane.

You keep saying this, but it's only partly correct.  Properly constructed vents do both, and I can assure you that the bulk of the gas flow in a sewer vent is out, not in.

Traps keep methane out of a building. The reason vents go through the roof is because they must be kept higher than the highest drain, not because they vent methane. This is a common myth and may even be believed by some plumbers.

Again, the reason vents go through the roof is to allow sewer gas to escape at a level higher than the living quarters.  If what you say was true, we could simply vent waste pipes into cabinets, or even the attic -- yet the UPC is exceedingly clear on this issue:  vents must proceed continuously to above the roof line.  Period.

Drain vents in an RV serve the same purpose, without them the traps would be sucked dry every time water went down the drain system.

Yes.  But since they are, by definition, also connected to the waste line, they ALSO VENT SEWER GAS.  There is simply no way to avoid this and have the vent work properly.

These vents could go out the side of the RV if desired since they take air in, not out.

Again, gas flows BOTH WAYS in a vent.  And the gas that flows out is sewer gas.

Check valves can also be used which take air from inside the bus and avoid more roof holes and long vent pipes. I use these valves.

What you call "check valves" are referred to in the trade as Air Admittance Valves (AAV's), and discussed in the code as "anti-siphon trap vent devices."  They are indeed, permitted in certain situations.  However, THEY CAN NOT SUBSTITUTE FOR A VENT THAT GOES ALL THE WAY TO THE ROOF.  You still must vent the fixture at the earliest opportunity:

7.7.5 Anti-Siphon Trap Vent Devices. An anti-siphon trap vent device shall be permitted to be used only as a secondary vent ...

(underline emphasis mine).

If you do not know or understand what a "secondary vent" is, I refer you to the UPC.

...
The reason for large building roof vent pipes is that the vents are so long and the drain pipes so large that a small vent pipe would not allow enough air to enter the drain pipe as the liquid flowed out. My bottom vent pipe is only 1.25" and perfectly adequate because it is so short.

I am not sure what you mean when you say "large building roof vent"  -- are we back to buildings, or still talking RV's?  Because my code says the vent must be a minimum of 1.25", the same size you used, although adding enough fixtures or certain wet venting requires one trade size higher -- 1.5".  But, again, it must go through the roof, as I cited earlier.

Any pressure of any kind in a waste tank will evacuate methane if it is present, including incoming liquid.

Precisely what I said.  And, if that evacuation happens below the coach, then methane and other sewer gases can then rise right back into the coach.

The theory that it will accumulate in the loop is just a theory, nothing more. The theory that there is enough methane in an RV waste tank to be hazardous is also just theory, nothing more.

Just to be clear, while I have cited the problems involving methane for completeness, my bigger concern (as well as the code's) is not methane itself, but other sewer gases, including hydrogen sulfide, and any pathogens that might be along for the ride.  Sewer gases entering residential spaces is a proven problem from which many people have become ill -- it is not a "theory."  This is one reason why the codes mandate that vents proceed directly to the roof.  A simple Google search will turn up hundreds of cases of people becoming ill and even being hospitalized when sewer gas entered an occupancy space, including school and office closures, residential condemnations, etc.

If anaerobic bacteria is allowed to grow in an RV waste tank there won't be any significant methane,

Now, this one takes the cake, because the primary byproduct of sewage digestion by anaerobic bacteria IS methane.  (By contrast, aerobic bacteria would produce carbon dioxide.)

or solid waste for that matter. The problem is that most RVers seem to insist on cleaning the waste tank at every dumping or adding strong chemicals. Bad. This kills the little ab who will do the job much better if only allowed to live. I never completely empty my waste tank.

Here, I agree with you -- the health of the tank will be best served by keeping the bacteria alive, which means don't put harmful bacteria-killing chemicals in the tank.  But please don't tell us this does not produce methane and other sewer gasses -- this is exactly what it produces.

There is nothing to indicate that methane in an RV waste tank is a problem.

I would say the code itself indicates that.

I've never heard of an RV explosion caused by methane?? I've also never heard of a methane explosion in a home for that matter. Just because it is posted here that it is a danger doesn't make it so. These are opinions.

A simple Google search revealed dozens of homes that have suffered methane gas explosions or fires from sewer problems.  You can certainly look them up.  That's fact, not opinion.  As for RV's, well, I confess I could not find any reference to RV explosions due to methane in a brief search.  But, again, the primary safety concern is not methane, per se, but other sewer gases along with airborne biologic pathogens.

Saying that a bottom vent is incorrect or unsafe is baseless. Saying it is doesn't make it so.

I'm always amazed when a poster says another poster is wrong with no base for such a statement.

It's not "baseless" -- it's in the code.  The code is the "basis" for my statements.  And, the code makes it "so," whether I say it here or not.

Disagreeing is one thing, saying another poster is wrong is another thing altogether and not necessary. I was under the impression that we post here for the information of the questioner and that it was up to him to decide what is right and what is wrong?

Gus, I did not "decide" that it was "wrong" -- the code says you should not do it.  That makes doing it unlawful.  That's what I said -- it was you who contradicted that, and asked for an explanation.  Now that I have acceded to your request and explained why the code says what it does (bearing in mind that I did not write the code, I only quoted it), you are accusing me of making things up.

Codes are very often more political than technical or safety based. Copper vs PB water supply pipes is the best example I can think of. PB is superior in every way to Cu yet it is not approved in many location. Why? Because it protects the Cu suppliers.

Setting aside, for the moment, the fact that I do not buy into these sorts of conspiracy theories, and assuming you are correct, please explain to me who is benefiting "politically" from the requirement to extend RV vents to the roof.

One can make a choice, blindly follow mindless codes or think! It is easy to follow mindless rules and regulations but a bit more challenging to think.

As I have said on this board many times, I don't buy this notion that any of us can ignore all rules and regulations and do whatever we want simply because we can "think" and that thinking leads us to believe that we know better than the law.  That is a slippery slope.  Right now, it's plumbing.  Later, maybe it's headlights, or air brakes, or propane.

I'm not a fascist, but neither do I want to live in anarchy.  I don't want to live in the world you propose, where anyone at all, regardless of qualification, gets to build anything they want.

I would also like to know where you got the notion that the codes are "mindless."  That flies in the face of reality, and is disrespectful of the people who have spent countless hours working on them.

... My ole Grandpappy told me long ago to beware of experts and engineers!!

Great.  I invite you to take a ride on an airliner, roller coaster, or elevator designed by people who did not finish engineering school.  If you could even find one here in the U.S. -- doubtful, precisely because our concern for the safety of the general public here generally keeps such things from entering service.

Actually, for that matter, you should give up bus ownership right now -- those darn buses were designed by, gasp, engineers.

-Sean
http://OurOdyssey.BlogSpot.com

[Dreamscape]

Many codes were designed because of someones death, so therefore OSHA and others to protect us from making stupid mistakes and saving lives, could be yours! I prefer to be safe and not argue over stuff that has already been thought through. I'm vented thought the roof! And can sleep better at night, wake up in the morning without a headache or worse, not waking up!

~Paul`

[FloridaCliff]

There are sometimes many ways one can do something.

But sometimes there is only one right way, like it or not..

Hey, even the porta potty guys run there vent through the roof......

[Blacksheep]

Cliff that's why they call me Blacksheep! I guess everything I do and have done is wrong and won't work! Stems all the way back to my tanks and how they were done and they would never work but guess what, still hanging, still no leaks and best yet, still haven't killed anyone on the interstate!
I'll just keep my vent going out the bottom of my porta potty and see you down the road!

Ace with his mobile methane conversion!

Geez....

[Len Silva]

By now, everybody here knows the right way to do it and where to find all the information you will ever need.  There is one right way and a hundred less right ways to do it.  There can be no argument with doing it right.  There are multiple arguments with doing it less right (I didn't say wrong).

I must point out that if I were looking at a used conversion that didn't make an attempt to follow the various codes, I would scrutinize it far more carefully than I might otherwise.

[JackConrad]

Hey Ace, maybe if you ducted the vent into your engine air intake, all that methane would increase your HP?  LOL  Jack

[happycamperbrat]

Hey Ace, maybe if you ducted the vent into your engine air intake, all that methane would increase your HP?  LOL  Jack

That is kinda what I am wondering...... I dont really want to put holes in my roof either (if not necessary). I have an RTS and my engine is way in the back, so would there be a problem if I ducted my system to vent near the top part of my engine compartment or out the top where the AC is into the already vented area up there (though I guess if I ran the factory AC I would just be throwing the gases back into the living areas)?

[BG6]

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 is lighter than air, and odorless.  It is not toxic, but displaces oxygen and is explosive in concentrations between 4.5% and 14.5% in free air.

If you are venting below the tank, your vent pipe will trap methane rather than venting it, filling both the pipe and the tank.  The only gas to be released will go out through the drains -- into the coach -- or that which is forced out the vent.

Venting upward keeps the concentration below 1% while venting downward puts the concentration at anywhere between 1% - 100%, depending on factors such as when it was last drained.  Also, if you are venting under the coach, that methane may get inside through any seam, hole, crack, etc.