Hiding Galley Vent Pipe in Wall

[justgoclimb]

I'm currently redoing the plumbing on my 72 Overlander and I'm stuck on what to do with the galley vent stack. I thought it ran behind the inner skins, but there is no way 1 1/2" pipe and fittings can fit in that space. My service manual doesn't specify the pipe size for this vent - just labels it as "pipe, vent, bend, galley."

I want an open layout here and don't want to see a pic pipe running to the ceiling. Does anybody know how this originally worked? I don't have the old pipes for reference because the trailer was gutted when I bought it. Any ideas on alternate solutions?

[Tom Nugler]

The vent pipes do go through the walls in the galley. My repair manual shows a galley vent pipe(#28, probably same manual), pre bent, going up to the roof.
While I haven’t seen this in my ’72, my ’67 had a collection of bent and flattened vent stacks for the bathroom that ran in the walls and closets. The pipe ends are round as they exit the roof into the vent covers.
I suspect Airstream has gone the same route for these years as well.

As far as plastic piping goes I know that the older ABS piping in the Vintage rigs will deform with heat better than the modern PVC. Maybe using an electric paint stripper heat gun on a pipe while compressing it between some wood will produce the results your looking for.

Tom.

[Minno]

I believe we re-used our vent stack, and, yes the pipe was flattened a little. It does go up in between the inner and outer skins. I also remember having to seal all the holes in it because the factory put up the inner skins with rivets through the stack. Best to avoid that!

Kay

[vinstream]

I have a very simple solution to your problem... Remove the vent stack!!! If you use a Hepvo Valve and have your tank vented you will no longer need a vent stack. I use them on every drain and love the simple way they work and will never dry out the p trap and stink up your trailer.. Hepvo Waterless Valve

[Lance M]

I've used the Hepvo and they work very well. You will still need to vent the gray tank some way. In '72 the galley vent stack goes into the wall below the level of the galley counter. It is a one piece, formed oval ABS pipe.
Check out Aerowood's thread for how he did his vent.
http://www.airforums.com/forums/f416...nte-26902.html

[justgoclimb]

Tom, thanks for clearing that up and enlightening me a bit. Just took a blow dryer to some PVC and managed to bend it in sections to fit along the wall. However, it still protrudes a little bit past the ribs. For 1.5" pipe to truly fit within the 1.5" walls it must have to be flattened a bit.

But now I'm thinking about scrapping it anyway and going with the waterless trap. It looks perfect. I'm curious though now how I should vent my grey tank? I am making the black tank in my 72 a grey tank, since it didn't come with one originally and I will be installing a composting toilet. Would I be able to use one of those waterless traps for a shower if I install one? I'm holding off on the whole bathroom for now, but will be adding it down the road.

[justgoclimb]

Looking at air admittance valves - seems like if I put one back by the grey tank it will solve all my problems, and I can just close/patch up my current roof vent holes. Any reason not to do that?

[Lance M]

The tank must be vented to allow water to occupy space filled with gas in the tank. You must have at least one roof vent for the gray tank. Two is better, but one is a must.

[Aerowood]

If I've done this paste right on my phone you should see my vents that run in between the interior and exterior skins

http://www.airforums.com/forums/showthread.php?t=26902

Vents start around post 420

[HiJoeSilver]

Been thinking about vents for the last day or so as I get ready to reinstall my plumbing.
I've got one main vent stack that comes off the gray and black tanks and up to the roof. I'm good with having that vent.
One problem was that it was pushed down into the bottom of the tank originally, so as water rose above the bottom of the vent pipe air couldn't vent up the stack. New stack will get a second hose clamp on the vent pipe itself above the fitting it enters to keep it from going to far down onto the tank.
Originally the bath sink drain tied into the vent stack, stupid design because water flowing down the sink drain can block air from flowing up the vent causing air to bubble up in the shower. Luckily there is another tank inlet about 4" over from the vent stack outlet that was un used. This is where the sink drain will be going, and should have in the first place.
Vents that,even as an engineer, I don't get and likely won't be replacing are the stubby vents on the drain line themselves. They vent into the trailer. As long as the tank is vented there is no physical reason for them. If for some reason there was a build up of air pressure, say in the line from the kitchen sink to the tank(my longest drain line) it would push the water in the trap up and vent up through the sink. It will lift the water in the trap slightly until if can get past the seal , air escapes , water resettles sealing the trap again and the air escaping ends up in the same place as the stubby vent vents do, but no stubby vent to break and fill the trailer with stinky gas, which seems to happen a lot. The few inches of water pressure aren't enough to damage anything.
If the vent stack were to clog you would get the exact same thing if pressure built up in the tank, with or without the stubby vent, air venting into the trailer. The place where the vent stack being clogged being a problem is in the opposite direction. If the vent was plugged and you drain the tank it could create a suction on the tank and suck the seal out of a p trap, the stubby vents don't allow air to enter this way anyways so they wouldn't stop this.
I bought a HEPVO hoping it could replace the shower p trap so I didn't have to have a box sticking down but I can't figure a good way to install it since it only transitions to tube and not pipe and the space available. I really hoped it could connect right to the schedule 40 but doesn't.
The way the gray tank was in originally made it about impossible to remove because there weren't any connections to break and the tank had connections on opposite sides. It was also nearly impossible to get the pipe out of the tank inlets even with the tank removed, pipes having been cut to remove it. When I put it back all the inlet lines will be getting stainless steel reinforced mission clamps so that if I need to drop the tank I can undo the mission clamps , unbolt the drain valve and get it out easily.

[HiJoeSilver]

Originally Posted by justgoclimb

Looking at air admittance valves - seems like if I put one back by the grey tank it will solve all my problems, and I can just close/patch up my current roof vent holes. Any reason not to do that?

The vent on the tank is mostly to let air escape as water fills the tank. An air admittance valve won't work in that direction. You also want the vent higher than the highest drain going to the tank so if the tank gets over filled the water rises in the pipes until it, in most trailers will starts to flow into the shower pan. Also the tank vent needs to be to the outside. Easiest way to be higher and outside is through the roof.

[justgoclimb]

So I think I'm going to do away with the galley vent and use a Hepvo trap on the sink. There is another roof vent in the rear bathroom area curbside that I would like to use for the grey tank vent, but it wouldn't be coming directly from the tank. The tank is under the floor more towards the driver side of the rear. I think the vent I want to use was originally for the shower. Are there any issues with setting it up like this?

[HiJoeSilver]

I'll admit when wrong, the stubby vents aren't vents but vacuum breakers, at least 2/3 of mine. 1 mush have been replaced. Still I'm going to swap over to HEPVO as well. Figured out how to make the one on the shower work.
Interestingly looking at the service manual for my trailer, the us and canada model drain systems are identical except canada doesn't have the in line vacuum breaks.

[Minno]

We married our black and grey vents together into 1 vent when we replumbed, so I don't think distance is an issue with what you want to do using the rear vent. We haven't had any problems with it.

Kay

[justgoclimb]

Very happy to report back that I found an easy solution that I hope works. I found some flexible pvc at Home Depot - it was labeled as spa hose or something and you could buy it by the foot. It came in 1", 1.25", and 1.5" inner diameter. I went with 1.25" to make sure it would fit in between the walls, which it did perfectly. 1.5" would have been too fat.

I patched up the galley roof vent opening because I won't be using that one. Instead, I'm using the other vent opening that was back by the bathroom. This vent I think was originally hidden by the shower and actually ran outside of the wall, so there was a hole cut in the fiberglass endcap where it went through. But I wanted to run the pipe inside the wall since I'm downsizing the bathroom and that area will be exposed by the bed.

Anyways, I was able to get the pipe up through the vent and then run it down between the skins along one of the ribs. I just popped a few rivets so I could pull the endcap back enough to fit it in. It was actually much easier than I expected, luckily. The pipe bent along the curve perfectly and is now inside the wall. You'll see in the pic below that I need to replace the vent gasket to seal that area up there. But once that's done hopefully it'll be all good. I got a step-up fitting to take the 1.25" vent pipe to 1.5" so I can connect it to the rest of my drainage pipes. I was told I can use regular pvc cement with this flex pipe, so it really shouldn't be any different than bending regular schedule 40. And the rest of my PVC is white, so it fits right in. Black isn't really used around here.

This will be my one roof vent in the whole system. When it's all finished, I'll have two sinks and a shower draining into a grey tank. No black tank. I'll be using a Hepvo valve on all the drains so this will primarily be to vent the grey tank.


Flexible pvc coming out the bottom, not trimmed yet.

Pipe going out the roof vent, which clearly needs a new gasket.

[emmadow]

I'm replumbing our 1965 Overlander. Can I do away with the vent pipe by the kitchen and vent the kitchen sink to the rear vent pipe?

[Monza]

I'm in the middle of planning my '72 plumbing, so in the same boat.
I don't think you can- I assume your kitchen vent pipe is tied into the fresh water system, the rear vent is black and grey (if you install grey). I guess you could run a vent pipe from the kitchen to the back, but that seems like a hassle.


Maybe look at the Hepvo vacuum break mentioned early in the thread?

I could be totally wrong...

Good Luck.