Best Location for Plumbing Vent

[Melbo]

I am getting ready to install my plumbing vent.

I am trying to think about air movement while driving.

I have a ceiling vent fan that will be in front of the plumbing vent.

Should I locate the plumbing vent more toward the center of the coach or more toward the edge.

There is a window that is located behind where the vent will exit the roof.

Any suggestions or experiences will be helpful

Melbo

[gumpy]

Well, I can tell you my current situation. I located mine in the middle of coach, just off center. It's in front of the rear roof hatch. We're experiencing odor when driving, and I've determined it's probably being pulled back into the coach through a faulty and leaking gasket around the roof hatch. I can feel the breeze coming through the hatch when my wife is driving and I'm sniffing.

That reminds me... I need to change the location of the vent this fall.

craig

[jjrbus]

Not surre on the roof exit. But the gas/fumes rise making the pipe between tank and toilet a collection point. So when you flush the toilet you have the possibility of 1 to 2 cubic ft of gas/fumes entering coach. In hindsight if I were doing it again I would put a 3in to 1 1/2 inch tee as high as I could in the toilet pipe and vent from there.

[TomC]

I used 1 1/2" pipe.  Two are on the passenger side on the roof and one on the drivers side also on the roof.  All have the T shaped venturi vent that does not rotate from Camping World.  Works well.  Only time I get smell is when the windows are open and the gray tank is stinking.  Nothing a little Clorox doesn't take care of.  Two vents for the gray and one for the black. Good Luck, TomC

[belfert]

Well, I can tell you my current situation. I located mine in the middle of coach, just off center. It's in front of the rear roof hatch. We're experiencing odor when driving, and I've determined it's probably being pulled back into the coach through a faulty and leaking gasket around the roof hatch. I can feel the breeze coming through the hatch when my wife is driving and I'm sniffing.

That reminds me... I need to change the location of the vent this fall.

Where would be a good place to locate the vent?  I assume I need a vent at each fixture (besides the toilet)?

I'm not a plumber, but I will have a helper who has done some plumbing.

Brian Elfert

[H3Jim]

I have one 2" vent. 

Like Tom, I have a T shaped fixed venturi opening on the top.  Since I put the vent in, I have never smelled any gas or bad odors.  I have never put any disinfectant or odor stopper in either the black or gray tank. The vent is on the drivers side, along with the toilet and kitchen sink.  The bathroom sink and shower are on the passengers side.  All done with 2" pipe for lots of air and water flow.  I think, although can't prove, that the 2" pipe allows enough air flow in and out of the tanks that the tanks have aerobic bacteria, hence odor is not an issue.  I have flushed the toilet (an RV type that opens up and drops straight down)  in all kinds of conditions, moving, not moving, wind, no wind, full tank, empty tank, half full tank etc.

The vent portion is mostly straight up or I used 45's not 90's so lighter air ( gases) will ascend easily and rapidly.

Part of the vent is a wet vent, where the kitchen sink drains down a short section of pipe that is both drain and vent, but being 2", there is no problem in doing that.

On the passenger side where I do not have a vent, I stubbed off a pipe that could be used as a vent if need be - either through the roof, or the internal flapper type.  I have not needed it in a year of use, so I will just leave it stubbed off and finish my walls.

I joined the vents for the black and grey, above the tanks.  If one tank fills, it can overflow into the other, so technically because they are attached this way, they are both considered black tanks.  In practice, I keep such close eye on tank levels, overflow is not likely to happen.  I have tank sensors that are accurate enough I can tell almost to the gallon how full each of my tanks are.

The vent is about midway from front to back, and in from the side about 15".  It is not near a roof hatch,  or any windows. 

[prevost82]

I put 2- 1 1/2" vents out the bottom of the coach (one on each side of the tank) with "T's" on the ends for venturi's. We get no odor when parked but if we do get odor driving (I think it's coming from the toilet over flow vent) I turn the Fan-tastic Fan on so it's blowing into the coach, pressurizing the inside of the coach and no more smell.
Ron

[belfert]

I put 2- 1 1/2" vents out the bottom of the coach (one on each side of the tank) with "T's" on the ends for venturi's. We get no odor when parked but if we do get odor driving (I think it's coming from the toilet over flow vent) I turn the Fan-tastic Fan on so it's blowing into the coach, pressurizing the inside of the coach and no more smell.

What type of toilet?  I wasn't aware that toilets have an overflow vent.  I have a Thetford Bravura.

Why two vents for the tank?  I like the idea of under the floor as long as I don't get odors during driving.  Under floor would be a lot easier.  I assume the sewer gases naturally rise.  How do the gases vent if the vents are lower than the tank?

Finally, do I need to have vents at the fixtures if I vent the tank?  If I need fixture vents, can I use the cheater tye vents used for standalone kitchen islands?

Brian Elfert

[H3Jim]

I hated the idea of cutting a hole in a perfectly good roof, but I got over it.  For some time I had my tanks vented in front of the duals.  I had odors when parked and lots of odors when I flushed.  the 2" vent out the top really made a big difference.

Some toilets do have an overflow feature, my thetford aria does not.  When they do have the overflow feature, they are designed so there is water in an internal trap so gases can not escape, much the same as any sink trap.  Ony when the toilet has not been used in months and the water evaporates, does gas escaping become an issue.  I suspect that Prevost82's smell is coming from his vent pipes.  When a coach is moving there are many different high and low pressure zones and one of them is sucking air in from the area near the vent outlet.  Great idea to presurize the coach interior with the Fantastic fan, but I believe it should not be necessary with a properly designed vent system.  I like his dual 1 1/2" vent pipes, he can get cross ventilation which is good.

While there are the plumbing codes to follow, I think there is some art as well as science (or in my case luck) in the design.

[Melbo]

Thanks for all the info

I am going to install the passive vents at every trap to keep the air from sucking them dry

All of my vents will be tied together and vented through a 2" pipe out the roof

I also will have a 1 1/2" vent that can draw air from the outside up from the bottom

But it also sounds like a properly treated tank will prevent the odors in the first place

I still have not decided if the 2" vent will be better at the center or side of the coach

I can locate it any where I want now but not next month by then I have to know where to put it

Keep the info coming

Melbo

[Ace]

My black and grey tanks are one of the same. The vent is a two inch pipe coming out of the top side of the tank and then with 1, 90 "L" going straight down thru the floor with a 90 "L" turning it rearward. I put a baloney cut on the end of the pipe like a bike pipe and I have never had any odor what so ever under ALL circumstances! I didbn't want to go thru a perfectly good non leaking roof either! 

Ace

Forgot to say that this is on the drivers side just ahead of the rear wheels

[prevost82]

Brian..I put 2 vents one on curb side and one on the drivers side of the tank (tank is 24H x 23W x 60lg with baffles) Without the 2 vents, when I when around a corner it would suck the P traps dry on one side and compress the air on the otherside, putting 2 vent

I have a Sealand ceramic toilet, some where at the back of the bowl there is a small hole for overflow. I went straight up 4" then did a 180 down through the floor with a T on the end. I personally don't think it matters which way you vent it (through the roof or floor). I don't get any more smell out of my basement vent them someone with a roof vent....like Jim I just couldn't come to grips with a hole in the roof.
Ron