Is there any reason that the vent pipe that goes through the roof can't be vented through the wall of the lower section of the trailer or just replaced with an air admittance valve (AAV)? I'm taking the cabinet out of the bathroom in my 2088 and moving the toilet to make more room so I need to relocate the vent. I'd rather not make another hole in the roof if i can help it. Any ideas?

The vent pipe "exhausts" odors and other gasses from the toilet tank. As such, you want the outlet up high so they are carried away by the winds and not blown back into the trailer. If you took it out of lower section, you'd need a long exterior pipe to vent it high enough. I don't see how that could be a practical or attractive setup.

I don't know how AAV's work, so I can't comment on those, but keep in mind that the vent pipe is an exhaust pipe. From the name, it sounds like an AAV might be an inlet valve?

- Jack

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Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan, LiFePO4 battery 12V DC Electrical System, SoftStartRV mounted on A/C
2024 F150 Platinum FX4 3.5L PowerBoost SCrew

It is an inlet and is used in houses to let the pressure equalize in the system when water is draining and also to seal out sewer gases from coming in the home. I also found some valves that replace the P-traps that seal out the gases from the tank. My only question is if I dont use a vent to let the gases out, will the system pressurize and result in a blowout?

Hepvo Waterless Valve

TheAAV valve prevents the water from being sucked out of the p trap and in no way takes the place of the Vent. The vent exhaust the smelly gasses from the tank which are also explosive gasses. I see no way that you could exhaust the system thru the side of the bottom half. Due to the danger of a buildup of these gasses, this is a system that a amature should not change fool with. Remember the word explosive.

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Jim L & Faye
2805C
2003 Silvarado diesel crew cab
2017 Silvarado, crew cab 1500 6.2L gas w/ 8 speed tranny
central VA

If you look at the link Misfit provided. the AAV does not stop water from being sucked out of the p-trap.
I eliminates the p-trap.
I am a retired plumber/remodeler.
I eliminated the tall stand pipe in my hi-lo that penetrates the ceiling. I installed a negative pressure valve in the closet cabinet. It only allows air to be introduced into the system when there is a draw/suction(during draining). The neg vent must be plumbed higher than the tallest p-trap.
I did install 3/8" vent line, to vent pressure from tanks during high heat and material breakdown. Right below the neg pressure vent, and to exit under the trlr.
And JimL is correct that methane is explosive. At least you can smell the gas to alert you of the need to vent area!

I have NO ceiling vent for the black tank and it works excellent.
Use of a tank deodorizer/cleaner is still needed to make all of the system reasonable smelling, but only 2x per month or so during the summer during use! We only needed the cleaner once during our 2.5 month sojourn.

steve

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2002 ford f350, 7.3 diesel
1985 hi-lo funchaser
kb0nai
kd7ctk

The drain line from the kitchen sink is 1 1/2 inch but transitions to 2 inch a couple of feet from inlet to grey water tank (don't really know why). At this transition point the vent line comes up and ties into the vent pipe for black water tank, then straight up through the roof. There is a vent under the sink for the grey water tank (since this is just grey water, I wouldn't think methane would be an issue). Would I still need the vent pipe for the grey water tank since it has the vent under the sink?
As for the black water vent, I was thinking of using a washing machine outlet box and mounting it in the wall from the outside. Then bring my vent line into it and using the vent cap from the roof inside the box which will allow it to be recessed into the wall so there would not be interference when lowering the top half. I got the idea from the furnace vents that are recessed the same way.
All the plumbing and outlet box will be covered by an enclosure and the toilet will sit on top of enclosure raising the toilet height. Also, how can I transition from the black water tank flange to the new toilet flange approximately 6 to 8 inches higher? I removed the cabinet that housed the vent line and plumbing and want to move the toilet to the corner and increase the size of the existing vanity width wise.
I know the inlet to the tank is a 3" threaded connector. Is there an adapter pipe that i can buy somewhere to raise the toilet flange? I know I will have to tap a new hole and flange into the black water tank where the toilet is going to go. I'm not an amateur plumber, just amateur at RV plumbing. Thanks

As a non-plumber I can still tell you that a sink wont drain without a vent behind it. The air needs to replace the water in its stead.

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Jim in Memphis
Wife of 45 years is Brenda
Recently sold our 1997 24' Classic
2014 Ford F-350 6.7 Diesel Crew Cab

My kitchen sink has a rv style and size, of a neg pressure valve with the under sink plumbing, from the factory. This is the vent for the grey tank.
The one I installed is for the black tank. I used the existing piping, except for the end that rises upwards to the roof vent......which is what I deleted near the top in the cabinet.

Misfit have you checked out the layout from below? The tanks are very thin wall, and not alot of lateral room for changes to piping.
Everything is doable, and I wish you the best. Keep us informed.

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2002 ford f350, 7.3 diesel
1985 hi-lo funchaser
kb0nai
kd7ctk

All of the plumbing is above the floor. This all started because the floor around the toilet has been wet and I need to cut it out and replace it. To get to the floor I had to gut the bathroom. As long as its already gutted, I figure I would change some things around to make it more suitable to my liking. I have an 88 funchaser so it probably isn't much different from yours. There was barely enough room to sit on toilet with that useless wardrobe closet in the way. So I dissasembled the cabinet and would like to use the cabinet front to expand the tiny vanity cabinet. But the first thing is the floor. To change that i am going to have to get all the plumbing out of the way so I can carefully cut out the bad floor back to some kind of floor supports. The bad thing is the floor literally sits right on top of the black water tank. Cutting floor out is going to be very tedious. Thought about dropping the tank but that looks like a ton of work. So its touch and go and trial and error I guess. I'm open to suggestions on how to proceed here. Been doing remodel work myself for years but this is a whole different ballgame. I know my way around a house. If you tear into this thing the way you do home demo you can cause a ton more problems. As one remodeler to another,HELP! LOL

If you look at the pictures posted here by Mike, the bathroom pics are kinda what I am trying to acheive here.
http://www.hilotrailerforum.com/f2/1...ker-free-1001/

Misfit
there are no floor supports to attach to. The floor is one piece. when you cut the floor you will have to install a block to nail to.
There will not be any room above the tanks for this to happen that I could see.
I agree that the closet and toilet/tub arrangement is very tight.
I had thought about moving these same items. Thus my comment about taking a good look at the under side to see what might work for you.

In the long run it may be that removing all of the offending existing structures, tanks/tub/closet, may be the easiest and most efficient means to come up with what you want. It will make repairing the floor much easier for sure.

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2002 ford f350, 7.3 diesel
1985 hi-lo funchaser
kb0nai
kd7ctk

An AAV will enable it to drain but the tank will still need a vent. There are a couple of reasons for this: 1- A holding tank can build up pressure that needs to be relieved, 2- There are two general types of bacteria in holding tanks: aerobic and anaerobic. The aerobic bacteria break up waste and turn it into CO2. They need oxygen to thrive. The anaerobic bacteria produce noxious gasses. They like an environment with little or no oxygen. In other words, a well ventilated tank should have less odor.

Raul

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Raul

2408T
2010 Nissan Frontier, 4x4, Crew Cab

Ren, There aren't any floor supports? What is there to attach a block or the new floor to? Should I not cut out the old floor and just cover it up with new wood? Maybe a hardwood in the bath area over the existing floor may be the way to go if there aren't any floor joists to attach to. What do you think?

Many including DH have had to do this repair. This has been discussed on 6-11-2011 by Robod. Another thread is 7-12-2014. It goes into to great detail and should answer your questions. Didn't want you to not have an answer to your question.

Misfit
sorry my computer was freaked out.
You have more to deal with than just the floor. You were talking about changing the location of the toilet. Have you viewed the black tank location from below.
I don't know if you can change the flange location on the tank. I doubt it.
But others may have done it.
There may be a tank configuration that when installed will give you the access???

keep us updated, someone else may want to duplicate your work.
I know I am interested!

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2002 ford f350, 7.3 diesel
1985 hi-lo funchaser
kb0nai
kd7ctk

Began the plumbing today and I think it turned out well.

Attached Images

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All of that PVC sure looks a lot cleaner than anything I would have done!!

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Fantastic Wife
2005 Toyota Tundra V-8 4.7L
2705T Tow Lite
1999 21T Tow Lite

Just dont look behind me where I accidently kicked over the can of purple primer and it rolled all the way across the floor leaving a purple line on my vinyl flooring. LOL. Good thing I was planning to replace the flooring cause its most definitely ruined.

Perfect opportunity to put in a wood floor.

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"Ruben"
2404T, 2003 2500HD 4X4 GMC Sierra SLT Crew Cab w/Astro camper shell and 2003 Chevy Tahoe LE 4X2
Far West Texas

No matter how careful I am, I always get the purple primer on more other stuff than on the PVC.

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Fantastic Wife
2005 Toyota Tundra V-8 4.7L
2705T Tow Lite
1999 21T Tow Lite