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Author Topic: tank vent help needed  (Read 5087 times)
crown
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« Reply #30 on: February 03, 2010, 09:44:26 AM »

 thanks one more time sean mine is a microphor L F 220
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« Reply #31 on: February 03, 2010, 11:12:16 AM »

Check vents, work like a charm, save lots of work, still need to vent tanks.        http://www.mobilehomerepair.com/checkvent.html   Available at the big box stores for a few $$$$
« Last Edit: February 03, 2010, 11:59:21 AM by jjrbus » Logged

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« Reply #32 on: February 03, 2010, 11:27:04 AM »

Air Admittance Valves, or "check vents" or whatever you want to call them, are there only to vent a fixture so that it drains properly.  They have absolutely nothing to do with venting noxious gases from a storage tank.  Totally different application, and they contribute zero to that function. 

Anyone who ever lit a fart on fire knows methane is flammable, and if you want to ride around with a tank of it under your floor, that''s your business.

Brian
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Sean
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« Reply #33 on: February 03, 2010, 01:26:55 PM »

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, ...


This, I agree with completely.  I have always recommended to folks here on the board that they actually purchase the latest copies of these publications for themselves.  NFPA 1192, the RV code, is available as a PDF download for $37 directly from the National Fire Protection Association:
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=1192

NFPA 70, the National Electrical Code (NEC), is also available as a PDF download, for $85:
http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=70

The NEC, however, is also usually available in most public libraries.  Just make sure you are looking at the latest edition, which is 2008 (the next one comes out in 2011).  You may find it's cheaper to just photocopy the pages you need, as the entire NEC is enormous and contains many sections that are not relevant.

The RV code (1192) is not as widely available in libraries, and moreover it is almost entirely germane; well worth the $37 to have your own copy.

Having said all that, I know there are lots of people here who just will not buy these books.  So I will continue to write, here and in BCM, about code related issues.  Beyond that, some of the code is hard to read, and can benefit from plain English interpretation (yeah, yeah, I know -- some of what I write is hard to read, too).  In the course of the eight years or so that I have been on this board, I've probably gone to these codes a couple hundred times just to answer questions from other members.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #34 on: February 03, 2010, 02:09:55 PM »

This tank vent thing has been kicked around endlessly.

The fact remains that a bottom vent is no problem and numerous installations have proven this.

I'm still waiting to read about a methane gas explosion caused by a bottom vent!

This vent is as much for taking in fresh air as it is for venting sewer gas. My book on home plumbing doesn't even mention that the vent exhausts sewer gas. When anything goes down the drain it creates a vacumn and the vent takes in air so the traps won't be sucked dry.

There is more hot air about this subject than there is methane!
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Sean
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« Reply #35 on: February 03, 2010, 02:34:05 PM »

This tank vent thing has been kicked around endlessly.

You mean in this thread:

http://www.busconversions.com/bbs/index.php?topic=12131.0

where I took you to task for all the assertions you just made again, even though they are provably wrong and still contravene the law?

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The fact remains that a bottom vent is no problem and numerous installations have proven this.


A bottom vent is illegal, and numerous installations have simply proven that the problems are rare.  Rare is different from impossible, which is why the code reads the way it does.  The fact that millions and millions of buildings have never been hit by lightning does not mean that lightning never hits buildings, which is why building codes require lightning protection.


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This vent is as much for taking in fresh air as it is for venting sewer gas. My book on home plumbing doesn't even mention that the vent exhausts sewer gas.


My book on baking doesn't explain why baking powder makes things rise, either (only that it does).  I can assure you that
  • Your book on home plumbing DOES tell you to vent through the roof, even if it does not detail all the reasons why.
  • The Uniform Plumbing Code (UPC) DOES mention that vents exhaust sewer gas.

As I told you in that thread, I invite you to vent your fixtures directly into your house for a few days, and then tell me that no sewer gas comes out.  (Please stay somewhere else, though, during the experiment.  I don't want you to get sick.)

As has already been written in this thread -- don't take my word for it.  Get the code; it's all there in black and white.  And do a little research and you will find that, yes, buildings have exploded from build-up of sewer gases, and many more people have simply gotten ill from them.

-Sean
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« Reply #36 on: February 03, 2010, 02:45:00 PM »

thanks one more time sean mine is a microphor L F 220


The LF-220 is an electrically operated, direct-drop model.  Unlike manual toilets from Thetford and others, this model tends to use quite a bit of water; the spec is half gallon per flush.

The amount of water entering the bowl after the flap closes is controlled by a timer.  If you use city water pressure (rather than exclusively relying on your internal water pump), you will find a wide variation in pressure and flow rate as you move from site to site, which will vary the amount of water in the bowl.  For this reason I strongly recommend you put a pressure regulator on the toilet supply line.  We use a compact model made for irrigation systems by Watts.

The manual for this toilet can be found here:

http://www.microphor.com/pdf/LF-220_Manual.pdf

HTH,

-Sean
http://OurOdyssey.BlogSpot.com
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gus
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« Reply #37 on: February 03, 2010, 02:53:27 PM »

I'm pretty sure I didn't say no sewer gas vents through a vent.

I guess I better move my vent, I certainly wouldn't want to have anything that is not exactly according to code.
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Sean
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« Reply #38 on: February 03, 2010, 03:12:10 PM »

I'm pretty sure I didn't say no sewer gas vents through a vent.


You didn't?  I guess I misread this, then (emphasis mine):

... 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.


In fact, you argued this point with me for several more posts.  Perhaps you are starting to believe?

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I guess I better move my vent, I certainly wouldn't want to have anything that is not exactly according to code.


As I wrote in the other thread, I would carefully inspect a completed conversion and assess all aspects of the venting system before deciding if an unapproved vent needs to be fixed.  As I have already acknowledged, problems are rare, and there are certain to be other issues of more pressing concern.

As I have also written, nothing, and I include my own bus in this, is ever going to be "exactly according to code."  But it is irresponsible of you to be handing out advice that flies in the face of the current state of understanding, and dismiss it as "no problem," especially when that advice contravenes the law.

-Sean
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« Reply #39 on: February 03, 2010, 05:16:10 PM »

This solves the requirements....I think.

Black water tank vent thru the roof.  Grey water tank vents thru the roof.   Each P trap is followed by a vent through the roof.  All  my vents are 2 inch.  All vents run vertical and the toilet is a straight drop.  If you must deviate from this you need to compensate or you are taking your chances.  No straight drop....microphor.  No vent after P trap....anti siphone valve.
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« Reply #40 on: February 03, 2010, 07:46:24 PM »

Black water tank vent thru the roof.  Grey water tank vents thru the roof.   Each P trap is followed by a vent through the roof.  ...  All vents run vertical ...


Just to clarify:

Vents do not need to remain vertical.  They only need to continuously slope upwards.  Nearly horizontal runs or runs at angles such as 45° are permitted.  Vents may also come together into a combined vent stack, as long as certain rules are followed about minimum sizing.

So, no need to make your roof look like Swiss cheese; in a carefully designed system, even one with two separate tanks and three fixtures plus toilet, you can still get by with one single 1.5" vent through the roof.

We chose to use separate vent stacks for black and gray, principally because the air-flush toilet moves a lot of gas out the stack with every flush, and I wanted no possibility that back-pressure at the roof cap could push sewer gas back down the gray stack and out a fixture drain with a partially empty trap seal.  So I actually have two 1.5" vents terminating through the roof (just a couple inches apart).

My kitchen sink is over eight linear feet from the vent stack (and tank connection -- it's a wet vent), and around two 90° bends (the sink is right in the middle of the bus, at the end of a counter that separates the galley from the salon), and I had no trouble getting proper slope on both the drain and vent sides of the waste tee all the way to the stack.  No AAV needed.  FWIW.

-Sean
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Nellie Wilson
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« Reply #41 on: February 03, 2010, 08:59:05 PM »

Sheesh.

Where the heck is that code book when you need it? Guess I'll just steer clear of the Tex-Mex and salsa. Or go find a public flusher.  Smiley

You go, Gus!

Nellie

PS. For the record, my tank is properly vented (per this as yet unveiled code) by a 1.5" pipe, traveling in a continuously upward direction, whereupon it farts straight into the face of the failing ozone layer. (Oopps, that may open a whole new can of methane).

Happily, I have no "motor-driven air intake that opens into habitable areas" - except, occasionally, my dinosaur of an engine -  so I needn't be "downwind" of anything, except the blunt (but aerodynamically designed) snout of my bus.

Amazing though, isn't it, how codes and laws and such are always drafted by lobbyists? And championed by folks having a horse in that particular race? So just call me cynical... or maybe I just have a different world view?

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Sunchaser Art
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« Reply #42 on: February 03, 2010, 11:33:10 PM »

For what it's worth, I used spa hose and routed it through the pocket door wall and up to the roof.  Seems to work fine, PVC glue to attach on the top and bottom, and real cheap.  Here's a link to the work in progress:

http://www.webcove.com/eagle/images/2007-11/04/11wallwvent.htm

Good luck,

Art
www.webcove.com/eagle
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Nellie Wilson
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« Reply #43 on: February 04, 2010, 03:54:04 AM »

Hey Sunchaser -

That looks pretty nice! Smart place to put it, too.

Wish I'd had my tank before building stuff inside, but things went the other way around... so I had to tear stuff out to run the vent. Much better your way.

Nellie Wilson
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« Reply #44 on: February 04, 2010, 05:03:59 AM »

 thats what i am doing useing spa tubing thanks all i learn a lot hear
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john
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