What's preferred method of venting black/gray tanks? 2" pipe through the roof?
Not crazy about the idea of drilling holes up there, or a pipe from floor to ceiling in the bathroom, but if that's the only way...?
Thanks
Our goes from the tank through the floor and then the roof with a vent cap. Have seen some vent out the wheel well area in the rear too. Mine is a 1-1/2"ABS And the grey "ys" into the black vent pipe so only one goes up and out.
through the roof. check all the rv's and tt's. they are almost all through the roof. when vented in a wheel well or such, there will be times where you will smell the odor. Hole? No big deal with all the other openings already. Change things up in the future? just add a patch with rivets or screws and sealer. Nobody would see the patch anyways, and I wont tell...
I know that most modern RVs and TTs have a vent through the roof, but our combined gray/black tank has a single 1/2" tube which goes out the top of the tank, takes an immediate u-turn, and then exits out the floor of the bay. The bottom of the tube is cut at a 45-degree angle to promote suction as the bus moves forward. We don't have any issues with odor coming from the vent.
P.O. on mine routed both vents to a PVC pipe leading to the battery bay on my 4104, with a cap included for storage. Can't comment on the effectiveness in action yet, but personally I'd prefer the occasional whiff over an additional hole in the roof.
IMHO if it's a bus, no body penetrations, if it"s a conversion/tiny house - go for it and do what makes it functional. Our 1953 in-service 4104 started getting converted by yours truly in 1979. There are plenty penetrations through both long sides, the roof, the wooden floor, the bottom bay aluminum floor, & through bay bulkheads, etc. No leaks and are all there for a purpose - including a roof air, solar arrays for house & chassis, & a host of upgrades and remodels along the way. AFAIC it was a Greyhound intercity bus, now! It's a GMC converted coach... That's our story & we're stikin' to it. It's truly comfortable self contained home where ever we park it... :^
Ours started venting out the floor of the wet bay. Kept getting odor inside, eventually moved to the roof. Only issue now is I put it too close to the vent . Oh well. that's just exhaust vent now.
In order to ventilate the black and grey tanks with fresh air so the aerobic bacteria there can do their thing, I have a unique design. Each of those tanks has two 2" vents on its top surface; the black tank has a 2" vent pipe going up inside a closet and exiting to a forward-facing louver just below the roof gutter, both tanks are inter-connected by a 2" pipe, and the grey tank has a 2" vent pipe that goes down to just ahead of the differential and points back. When driving, air is directed by the upper louver vent down into the black tank, across the tank and out to the grey tank where it again blows across and then down to road level where a rudimentary venturi pump sucks out all the stinky air at road level. When parked the airflow is reversed, with cool air from under the bus entering the grey tank's lower vent pipe, passing through both tanks and exiting the black tank's upper vent, courtesy of natural convection. So far, so good!
John
Geez guys you are venting for the methane gas just like your home not the odor .Passenger buses have a sealed tank with a suction fan to pull the methane gas from the tank,holding tanks have lot of nasty gases that are lighter than air which means it rises
We went straight thru the roof with a metal building boot, however under way it seems that it is pressurizing the waste tank. Not sure how to solve that problem
Quote from: 6805eagleguy on April 29, 2021, 08:05:56 PM
We went straight thru the roof with a metal building boot, however under way it seems that it is pressurizing the waste tank. Not sure how to solve that problem
Put one of those spinning nose&fin things on top of it, that will ensure the wind passing it sucks outward instead of pushing in. Had that issue on my old RV and that fixed it nicely.
Thanks everybody!!
Quote from: 6805eagleguy on April 29, 2021, 08:05:56 PM
We went straight thru the roof with a metal building boot, however under way it seems that it is pressurizing the waste tank. Not sure how to solve that problem
Pressurizing the tank, or hurtling down the highway is dragging a vacuum on the coach interior?
Having the driver's toll window open when someone steps on the pedal... various busnuts have been able to splash the occupant of "the little room" ...
After spending time with the boat folks, i will put two large vent pipes into and out of the waste tank. Lots of air, no bad smells, little to no air, lots of bad smells.
The boat peeps have to manage this more closely, as they don't "dump" , they get "pumped" , so harder to send it all away...
Happy coaching!
Buswarrior
Quote from: Nova Eona on April 29, 2021, 03:48:43 PM
P.O. on mine routed both vents to a PVC pipe leading to the battery bay on my 4104, with a cap included for storage. Can't comment on the effectiveness in action yet, but personally I'd prefer the occasional whiff over an additional hole in the roof.
Seriously? You might want to rethink this one. As Clifford said above that is Methane gas coming out there. Just takes a spark and the right timing and batteries sometime have those kind of events.
I planned to block out the two rear 1/4 round windows and decided that they would make a good spot for venting the on demand water heater and holding tanks. So far so good--no leaks and no stink. Jack
(https://i.postimg.cc/SNTY0xVF/4(3).jpg).
(https://i.postimg.cc/CxRBwp6Z/IMG_7668.jpg).
Quote from: Dave5Cs on April 30, 2021, 09:20:10 AM
Seriously? You might want to rethink this one. As Clifford said above that is Methane gas coming out there. Just takes a spark and the right timing and batteries sometime have those kind of events.
The pipe terminates right next to the louvered vent on the door, developing a methane concentration high enough to be problematic seems unlikely. I could easily elbow it into the wheel well to the side, but I've been rebuilding the water system over the winter so I have yet to even try it out properly yet.
In all my years as a mechanical contractor, I cannot tell you how many times people (customers) would ask if their roof would leak, or it there was any other way to vent a gas unit without cutting holes in the roof. I would explain to them that probably every house in the world (?) has multiple holes cut in their roofs for plumbing vents, gas vents and other types of venting and penetrations. It is such a common thing that it should be no problem at all. Having been in that position, I would install 10 vents out the roof of my bus, and then sleep like a baby.
Plumbing codes require that vents to go out the roof. I don't know what applies to RV's (there is no doubt some code out there regulates RV plumbing). I would suggest going out the roof, and then devising a way to create a suction effect for driving so that you don't cause the tank to become pressurized while underway (such as was suggested in other posts). Enjoy!
Here we go again, huh? Yes it's true that methane gas is lighter than air but guess what, it isn't the methane that stinks. It's both colorless and odorless. So while it can be a fire hazard if concentrated, it isn't what makes your waste tank stink.
Those gases are heavier than air. So you might have to re-think your strategy a little. To get them to move out the top of a roof vent there has to be some sort of airflow through the tank. And to encourage aerobic decomposition which gets rid of those stinky gases there needs to be airflow.
Also, if you let the stinky gases build up in the tank and you have a roof vent only, then they will eventually pile up in the vent tube all the way to the top and when you open the flush valve just the weight of the stinky gases will make them run back down the vent tube and push stinky gases out the toilet.
There are ways to solve this but what's most needed is a method that runs fresh air through the tank all the time both OTR and curbside and has no energy cost. That way the anerobic decomposition does not produce the stinky gasses in the first place and then they don't accumulate.
Ideally airflow would be out of a roof vent when curbside, and a suction would be pulled against the tank OTR. The best way to do that? Hard to say really. Lots of ideas have been tried.
Seems like it'd be a good idea to locate a low pressure area when moving, like at the rear of the bus, maybe up high. Would convection be enough? IDK. But it seems like a bilge fan tied to the bathroom light switch could help a lot. Just some ideas.
Jim
Sounds like a good application for a small solar panel tied directly to a fan somewhere.
Pretty sure that none of us hold the waste in the black tank long enough for bacterial decomposition. I know that I dump ours long before that happens.
The reason for the vent is pretty much to provide for a proper flow of waste into the tank. If the air can't get out, new liquid can't go into it.
My two "T" pipes come out in line with each other and 4 inches apart. I agree with " Let that methane go up and out". Only flaw is my pipes are near the vented roof/fan like most. When I forget to close the roof vent at a campsite and do not have the fan on, and a breeze comes from behind the bus, the roof air scoops it right back into the bus. If you already have a roof vent, keep that in mind before you punch holes in the roof. Lots of ways to waterproof those pipes on the roof. Worry not. Good luck with it!
Quote from: buswarrior on April 30, 2021, 08:37:19 AM?
Having the driver's toll window open when someone steps on the pedal... various busnuts have been able to splash the occupant of "the little room" ...
:o Yes that happened. Didn't relate it to the window tho. We have a 2 inch vent. What exactly would a second vent do?
Methane is not a friendly gas it displaces oxygen and will get you I saw a worker pulled from a 4 ft deep x 4 ft round manhole the methane killed so it is up and away for me now
Quote from: 6805eagleguy on April 30, 2021, 05:23:52 PM
:o Yes that happened. Didn't relate it to the window tho. We have a 2 inch vent. What exactly would a second vent do?
The second vent is to allow for lots of air flow, in and out, of the waste tank. The bad smells come from a lack of oxygen, lots of air, the wrong bacteria don't thrive.
This is aimed at stationary issues, not so much the ram air stuff.
Those who have lots of available oxygen in their waste tank, do not have bad smells.
The splashing? That is a powerful option available to the driver...with great power, comes great responsibility...
Happy coaching!
Buswarrior
Quote from: richard5933 on April 30, 2021, 02:25:29 PM
Pretty sure that none of us hold the waste in the black tank long enough for bacterial decomposition. I know that I dump ours long before that happens.
Bit of a misconception there since the bacterial decomposition actually began before you even ate the food. You'd really be amazed at how fast liquification occurs. In the city solid waste never ever shows up in the sewer. Only black water. How long do you think it takes to go from an apartment complex to the street?
Quote
The reason for the vent is pretty much to provide for a proper flow of waste into the tank. If the air can't get out, new liquid can't go into it.
Not really true either. A properly designed system will not stink. One with only one vent only large enough to allow inflow will always stink. You can only hope to contain and disperse it.
Jim
Go study the newer job johneys they have roof vent and even with toilet seat up, no odor.
Um, not exactly right? They have a chemical smell and have you seen the stuff they leave in those when they drop them off? No decomposition of any sort going on there would be my guess. A foul witches brew of some sort. But, if you'd rather cart around a few carboys of that stuff in your spare storage space why not? Oh, and with that open toilet there's plenty of air available for aerobic decomp if it ever did get started. Without that who knows what they would smell like? Not sure exactly what you're trying to say here.
Jim
I see that. The seat area is domed and vent pipe comes from that area through roof. With seat up, no fumes come up from that area even when 3/4 full or being used. Natural draft. Big improvement over old ones.
1 1/2" PVC pipe (one for both tanks) through the roof, 30 plus years no leaks with a T cap on top for venting, has worked for me.
I like the idea of a sweep T on top with the sweep to the rear creates a venturi effect
I saw a couple of roofers one time clean the vent pipe with an M-80 once when their buddy was using the pot-o-let. Not a pretty site. :o
Quote from: Dave5Cs on May 02, 2021, 01:15:45 PM
I saw a couple of roofers one time clean the vent pipe with an M-80 once when their buddy was using the pot-o-let. Not a pretty site. :o
ROFL 🤣🤣🤣🤣🤣🤣 ROFLMFAO