| Author | Message | ||
| christopher Rating: N/A |
does the vent really need to be a 2" pipe? the volume of water is not that great in a coach. would one inch 0r 1 1/2 be just as effctive? thanx chris | ||
| CoryDaneRTS Rating: N/A |
Which Tank are we talking about? If we are talking about Potable tanks, the only reason I would NOT tell you its ok to go smaller is because at some parks a water wagon goes around for your filling convenience. However, some of those wagons are high PSI for filling your tanks. If your vent can't dissapate the pressure, your tank will act as the relief vent. Grey system or black system you need to look at one thing. What size is your drain line to the dump???? Normal RV's have a 3" drain line so you have to figure the amount of air volume you will have sucking into the tank as you are dumping your tanks. If you have a macerator with a 1 1/2 inch hose, the vent can be much smaller. My old rv had the 3" line for drain and the vent on the roof was 1 1/2 I believe. I never had a problem dumping with that configuration. That in itself indicates to me that you need to figure 2 to 1, that is if 3" drain then 1 1/2 vent and so on. Any others out there have another idea, chime in. Good luck cd | ||
| ChuckMC9 (Chucks)
Rating: N/A |
If you're talking fresh tank, see this thread on why it needs to be somewhat larger. I'm using 1-1/4". ...hoping I don't get creamed for this pointer. | ||
| christopher Rating: N/A |
i was talking about the waste tank. mine has 2 2" vents. i wanted to make the kitchen sink one one inch and keep the batroom one at 2" i think it will work thank you gentlemen chris | ||
| Luis (Sundancer)
Rating: N/A |
You are going to have individual vents for the kitchen sink and bathroom? The way I did it is to drain into the grey tank and than combine one vent for the dark and grey to the roof of the bus. Then of course a small vent into the bay for the fresh water. Just adding my 2 cents. | ||
| John that newguy Rating: N/A |
You can also use the concealed vents. They can be installed in walls, cabinets, etc.. No need to go through the roof... | ||
| Gary Stadler (Boogiethecat)
Rating: N/A |
I installed one single 1-1/4 inch vent that serves both grey and black tanks. They are tee'd together just below the roof so I only had to pierce it once. Never any problems. I'd think twice about using concealed vents though- they are fine if only keeping the traps from sucking out but they won't work for a black tank that is creating methane... somewhere a vent must go thru the roof to vent outgassing stink-n-stuff | ||
| John that newguy Rating: N/A |
Took the gas right out of my a.. I should have added that comment, Gary.. Thanks for the clarification! | ||
| Sean Welsh (Sean)
Rating: N/A |
Christopher -- Minimum vent size, per code, is 1.25". That needs to be one pipe size larger (1.5") if you have a wet-vent system, or for use with specific larger waste lines. Luis -- you still need to have an individual vent for each fixture, and these vents must continue through the roof. They can be combined, of course, above the flood line of the highest fixture. If you try to simply plumb a waste line to the tank unvented, you will suck the trap dry. JTNG -- there really isn't any such thing as a "concealed vent" I believe you are talking about an air admittance valve (AAV), and these can only be used to "vent" specific fixtures under very specific circumstances. AAV's are uni-directional, only letting air in to the system, while vents are bi-directional, allowing air in to relieve back-pressure, but also allowing sewer gases out. As you have already acknowledged, a waste line using an AAV must still eventually be direct vented through the roof. All of this is spelled out in great detail in ANSI/NFPA 1192, though most of it is repeated from the Uniform Plumbing Code. 1192 permits things in RV's that the UPC would prohibit in a fixed structure (such as most wet venting), so 1192 is a better publication to have handy. It's available on-line for less than $50. Everything in these documents is there for very good reasons... -Sean | ||
| R.C.Bishop
Rating: N/A |
Residential code calls for 2", assuming it is not the "stack"///// My vent line= 2" down to 1.5"; goes thru the roof and is definitely "concealed". I use the original roof vent. I have six of them from front to rear of coach; three each side. ( Austin Hardware Nr. 23 Roof Vent..sans fan,page 433 in my catalog). No one knows but me.......  Do it your way!...and MAYBE suffer the consequences. RCB '64 Crown Supercoach (HWC) | ||
| TWODOGS (Twodogs)
Rating: N/A |
my holding tank vent is 1/2 " cpvc...does fine..exets bus in floor of last bay..when I have the ball valve on to fill the holding tank...know it's full when water is coming out the vent | ||
| John that newguy Rating: N/A |
From: http://www.toolbase.org/tertiaryT.asp?DocumentID=2127 "Air admittance valves (AAVs) are pressure-activated, one-way mechanical venting ports, used in a plumbing system to eliminate the need for conventional pipe venting and roof penetrations. Wastewater discharges cause the AAV to open, allowing air to circulate for proper drainage. Otherwise, the valve remains closed, preventing the escape of sewer gas and maintaining the trap seal. Using AAVs can significantly reduce the amount venting materials needed for a plumbing system, increase plumbing labor efficiency, allow greater flexibility in the layout of fixtures, and reduce long-term maintenance problems where conventional vents break the roof surface. " The topic morphed onto a discussion of kitchen/bath waste venting, aside from the holding tank itself. Why have drain vents poking holes through an otherwise waterproof roof, when one vent pipe serving both grey/black tanks will suffice, and AAVs can take care of drain flow? The holding tank vent pipe does not have to go through the roof and will work as long as it is sufficiently higher than the holding tank. Just don't put it under a window.. You can route it out the bus rear or high on the bus side wall (run inside; venting outside). | ||
| Jim-Bob (Pd41044039)
Rating: N/A |
Going back to the thread about the fresh water tank vent that siphoned out the water: If you use a 3/4" pipe, put a tee at the highest point & install an "AAV" (or siphon breaker) at that point. If the tank overflowed, the AAV will admit air & break the siphon. This is commonly used with marine toilet & engine plumbing to prevent siphons which could sink the boat. (siphons back into boat if not broken.) Jim-Bob | ||
| Sojourner (Jjimage)
Rating: N/A |
It only siphon when tank is collapsing (thin wall type) or do what Jim-Bob post about breaker or 2” vent to avoid siphon, which is air passage over water level flow in larger vent horizontal pipe. Usually ¾” is sufficient for strong-build fresh water tank. 1 ½” or larger vent for waste is best to avoid back-spray or flush while flushing. It you go thru roof type vent, install same size “tee” so “traveling-air” flow thru without create pressure in tank to avoid indoor smell. It being use on railroad caboose (long gone) and passenger cars. Found a photo of this set-up in http://www.fmca.com/fmc1999/augmag/tips.asp Scroll down to “Odor Prevention”. Or this http://www.rv-360.com/ or http://www.XTREMEVENT.com/ Or Boon Dockers http://wiffaway.com/ Or round hat type to match pipe size would work, similar to semi-truck air intake. Keep it low to avoid knock-off. FWIW Sojourn for Christ, Jerry | ||
| Sean Welsh (Sean)
Rating: N/A |
JTNG-- I did not say that each fixture needed a separate hole in the roof --- it is permissible to combine all the vents at some point higher than the flood rim of the highest fixture, and then they may exit the roof together. With regard to AAV's, as I said, using them does not relieve you of the requirement to still vent those lines directly to atmosphere. Here's the relevant section of the code: "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 in accordance with the following: (1) An anti-siphon trap vent device shall be installed in accordance with the terms of its listing. (2) One anti-siphon trap vent device shall be permitted to serve not more than two fixtures. (3) Anti-siphon trap devices shall not be used as a primary vent for toilets or holding tanks. (4) When a fixture drain or main drain bypasses a holding tank, that drain shall be vented by a primary vent. (5) Anti-siphon trap vent devices shall not be used on more than two consecutive fixtures before being vented to outside atmosphere. (6) Two fixtures protected by one anti-siphon trap vent device shall be drained by a common 1-1/2-in. (38.1-mm) minimum drain. (7) The device shall be installed in an accessible location that permits a free flow of air." Also, your suggestion to side-vent the system, rather than continuing the vent through the roof, also requires great care and imposes further restrictions: "7.7.6.1 Roof Extension. Except as otherwise permitted in this standard, each vent pipe shall pass through the roof and terminate vertically, undiminished in size, not less than 2 in. (50.8 mm) above the roof. Vents terminating on curved roof recreation vehicles or recreation vehicles with elevating tops must pass through the roof or upper side of the recreation vehicle at a point as high as practicable and not less than 6 ft from the ground level." Section 7.6.9 further spells out the requirements for side-venting of individual fixtures, but it makes little sense out of context so I will not copy it here. If you are going to dispense advice that sounds like code-speak, you should at least cite the relevant code -- the web site you referenced has to do with fixed structures only. Also, be aware that many, many jurisdictions do not permit AAVs at all in fixed construction, and some permit them only to solve intractable problems such as certain island drains. -Sean | ||
| John that newguy Rating: N/A |
There are "codes" and there are "things that work perfectly well"; I prefer the latter, when the former doesn't make good, practical sense. | ||
| Sean Welsh (Sean)
Rating: N/A |
John, What you "prefer" to do for your own situation is one thing (maybe). When you take it upon yourself to dispense advice to other people, then you either need to keep it legal, or be very clear that you are advising something which is contrary to code. If everyone in the world took it upon himself to ignore applicable codes and did things that, to him, only made "good practical sense," imagine what the world would be like. Would you board a commercial airliner built only to some individual's common sense? How about get into an elevator designed the same way? Or do you just take for granted that these conveyances are highly regulated, and derive some confidence that there are codes and regulations which these manufacturers MUST follow, no matter how much they believe some provision is "not really necessary"? And, yes, I've already heard the arguments that the life safety implications of these examples are on a completely different plane than, for example, AAV's in RV's. But deciding for one's self what codes to ignore and what ones to follow is the camel's nose inside the tent. Where does it stop? Am I free to put 400lbs of propane in an unvented compartment with a spark-producing device, and then park my rig right next to yours? Aren't you, my unknowing neighbor, entitled to the same protection of law as those people on the elevator? Think about it. -Sean | ||
| John that newguy Rating: N/A |
Up in the hills of Massachusetts when the snow packed the roof and covered the vents, all the codes requiring it up there defeated their own purpose. When the vents go through the commercial RV roof, and poke out directly in front of the air conditioner or fan intake, those codes defeated their own purpose. There are some of us that take note of the purpose of a "code" and make it's intention applicable to the job at hand. | ||
| Sean Welsh (Sean)
Rating: N/A |
"When the vents go through the commercial RV roof, and poke out directly in front of the air conditioner or fan intake, those codes defeated their own purpose. " That's why the code ALSO prohibits waste vents from terminating within 3' of any intake vent. You need to read the *entire* code, and not simply take pieces of it out of context. Codes are there for a reason. History is full of horrific tales of death caused by simple mistakes or oversights made by otherwise bright people. Codes have developed over many, many years to ensure that these sorts of mistakes and oversights are not easily made. Part of my participation in this forum is strongly advocating adherance to applicable codes. Shortcutting the code just says to me (and to code inspectors, not that you will encounter one) that you are either too lazy (or cheap) to actually follow the code, or not experienced enough to have understood the code in the first place. I'm betting, again, you would not buy a skyscraper from a builder who did not follow the building codes, but, instead, told you he just "...[took] note of the purpose of [the] 'code' and [made] it's intention applicable to the job at hand". Codes are not mere recommendations that can be followed only when convenient for the builder. When adopted, they are mandates that must be followed to the letter. Code authorities do not recognize you, me, or anyone else as being exempted from the code. -Sean | ||
| Johm that newguy Rating: N/A |
All in a day's work.... "Sept. 22, 1998, has to go down as one of the darkest days in the history of IAPMO. In a one-day period, the membership voted to turn back the clock 30 years on plumbing code advances. The criticisms at the end of the day varied from, "I've never seen it this bad," to "There goes another nail in the coffin," to "This is the worst I have ever experienced." They were all talking about the final actions on the code changes to the Uniform Plumbing Code." -------- "Logic doesn't matter There were many fine technical presentations made for various code changes. All for naught. Prof. Tom Konen of the Stevens Institute of Technology was seeking recognition of ANSI/ASME A112.18.3. He explained the details of this standard for regulating faucets with miniaturized backflow preventers. The changes were soundly defeated. Ed Saltzberg made an excellent presentation on horizontal wet venting and circuit venting. Unfortunately, he was followed by a fear-mongering presentation based on myths and innuendo. The technical presentation lost to absurdity, and wet venting and circuit venting were again rejected. The other rejections included: CSST (corrugated stainless steel tubing) for gas, air admittance valves, side wall venting, one-step solvent cement, macerating toilets and multipurpose piping for residential sprinkler systems. Basically, nothing new was added to the code. " From: http://www.pmengineer.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2732,9672, 00.html Do a "Google" and locate the vast amount of information regarding "codes" and how literally they should be taken. | ||
| Sean Welsh (Sean)
Rating: N/A |
John, There are good reasons why the income tax laws stink too, and why speed limits on many rural roads are too low (or too high, depending on whom you ask), and why the tort system in the US is hideous. Still, each of us is obligated to follow these laws. Certainly, we can work to change them through many channels, but we don't get to unilaterally decide to ignore them. The position you are advocating is unsupportable: that each of us gets to pick and choose what laws we will follow, without regard to consequence. There is a name for such a system: anarchy. Frankly, that's not the system within which I want to live, and, fortunately, for the most part, it isn't. As I've said before on this board and elsewhere, I'm no saint, and I've had my share of behavior that fell on the wrong side of the line. But I'm not going to get on this or any other public forum and advocate to others to deliberately ignore or violate those laws and standards that have been put in place for the good of us all, and neither should you. It's irresponsible, plain and simple. I'm sorry that your perception of your own righteousness won't let you see that. And please, don't sling babble that you've dug up on the internet at me -- I can use Google just as well as the next guy. One can find authoritative opinion on the internet to support any position at all. I know very well that this set of issues has been debated in code circles for ten years, and you don't even have any idea what *my* personal opinion is on the matter -- I haven't ventured it, since it's irrelevant. The standard is the standard, and, until it's changed, I have to support it (and follow it myself). Lastly, please understand that I am absolutley compelled to respond to this, on behalf of anyone reading this thread who is really and truly trying to determine his own path forward. If someone out there reads through this entire thread, and then decides for himself that, for example, he isn't going to vent through the roof at all, that's fine with me (well, I wouldn't go into his coach), but I will be secure in the knowledge that he made that choice knowingly, with as much correct and factual information as possible. -Sean | ||
| John that newguy Rating: N/A |
Sean- You're mixing Anarchy with Freedom, and Guidance with Tyranny. The "law" has to be logical. If law isn't logical, it is not law, but arbitrary rule by force. And that sir, is tyranny. The previous link displays how your "codes" come to be, and how logic and good engineering were set aside by the ego and power of those that regulate the "code". If a mistake is made in the formulation of a "code" that would result in injury if followed, would you suggest it is followed into it's injurious path? If so, you have been brainwashed into believing that the People should fear their Government, rather that the Government fearing the People. You prevent tyranny; rule by force, by taking the steps needed to thwart it as soon as it occurs. Following blindly; to encourage those around you to follow blindly rather than to use their own God's gift of logic and common sense, is aiding and abetting tyrannical control. There. I said it and I'm glad. | ||
| Ian Giffin (Admin)
Rating: N/A |
Thank you, gentlemen, for those excellent arguements. I think there has been a lot said on this thread to suggest to the novice reader here to consult a local expert, as well, where it comes to tank venting. Again, thank you and I look forward to reading your views on other threads. Best regards, Ian Giffin www.busnut.com | ||
| ChuckMC9 (Chucks)
Rating: N/A |
I@n, although it is unlikely that an offer by you to counsel some senior gov't officials to your south in the finer points (or blunter points ) of genteel diplomacy would be embraced with enthusiasm, there are those who would be grateful and appreciative recipients of same. | ||
| Luis (Sundancer)
Rating: N/A |
And this is why I really enjoy this BB. I must say I learned something new and enforced other old beliefs. | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
Thanks to these kinds of posts, our coach is getting better all the time. While this board is a bear to get caught up on when we have been gone on a trip, it is always one of the first things that I concentrate on when we get back. Thanks, fellas. Tom Caffrey PD4106-2576 Suncatcher |