Replacing Tank Vents and Sealing Old Mounting Holes

[SilverCabin]

I decided to replace both my tank vents with the newer Lippert 360 Vents that Airstream is now using. I needed to replace the black tank vent as I was getting some sewer gas in the trailer when the wind was from a certain direction, and I had a small leak in the area.

After removing the black tank vent, I'm pretty sure I found the water leak. The flange was cracked and not covered by caulk, and all the mounting screws showed signs of rust.

The photos below are the gray tank vent after removal and the mounting area. The first photo is the vent body after I removed it. Note all the cracks in the flange. Seems like the factory is using drill drivers to mount these and running them too tight. This is where the leak was on the black tank vent.

So now I have some questions for the group about mounting these new vents:

1. Notice the small void in the caulk on the right between the pipe and the roof. Both vents have the same void. Is there a reason that that's there, or should I caulk that to seal it up completely?
2. What's the trick to remove the film left from the caulk? I tried denatured alcohol, but it didn't seem to do anything.
3. The new Lippert vent body is smaller in diameter and only four mounting screws. What's the best way to plug the old holes? I was thinking of inserting a pop-rivet, then caulking them.
4. The old vent body crossed the roof seam, so when I removed the vent, some of the caulk was damaged. The roof seam caulk is still pretty tight and doesn't need to be redone yet, so can I just patch the seam caulk where it was damaged? Or do I have to remove and replace that segment?

Thanks for the help,

Randy

[SilverCabin]

Another thought. The old vents are mounted on a large circular gasket. You can see it at the bottom of the old vent in the photo above. The instructions that came with the Lippert vents just say to mount them directly on the roof in caulk, no gasket. I'm thinking about cutting down the old gaskets and using them between the roof and the new Lippert vents. If I had to remove one of them in the future, it would come off the roof a lot easier if it wasn't glued to the roof.

Any thoughts?

Randy

[SilverCabin]

Continuing my solo effort...

After doing some further research on this site, I discovered a couple of things:

1. The consensus on plugging the holes seems to be: push in some sealant, then a pop rivet, and then sealant over the top. This isn't a structural area, so pop rivets should work.
2. To remove all the old caulk residue, some recommend a CRC product, Brakleen. I bought a can, but I can't recommend it for the white-painted roof. It softens the paint so that you can remove it with a fingernail scratch. You might be able to see the area where the paint was damaged in my photos. I found that denatured alcohol and a little McGuires Cleaner Wax did the job satisfactorily.

I decided to reuse the old gaskets as they were in good shape, so I cut them down to size. To get the vent body flush with the roof this required removing that final glob of caulk around the pipe, where there was a void anyway. When I install the vent, I'll be caulking the gap around the pipe before I set the gasket in place.

I also discovered that Airstream was using screws that were too short. They were using #8 1/2" screws and had to torque them down hard to get a good bite. Sheet metal screws are supposed to be at least 50% inserted to get a good hold. I will be using #8 5/8" stainless steel screws. Then I won't have to torque them down so hard and crack the flange.

The below photos are the black tank vent pipe area ready for installation of the new vent, and the new vent dry-fitted to the pipe.

More later,

Randy

[SilverCabin]

Short workday today. Got all the holes drilled for the rivets to plug the old screw holes and to mount the new vents. After drilling the holes for the rivets, I realized that I could have just driven back in the old screws (or replaced them with new stainless steel screws) and sealed them with caulk. It might have been easier than what I'm doing now.

I did find that one of the screws holding down the old vent on the gray tank was right on top of a roof rib. I don't think it was even set all the way down because when I went to drill that hole for the rivet, I hit the rib and stopped. Upon examination, there wasn't a hole in the rib that the screw was in, so it was just holding on to the roof sheet metal and caulked. That's the hole that's empty to the right of the new vent in the picture below.

My plan now is just to fill that hole with caulk. All the old holes (soon to have rivets inserted) will be under the new sealant. The instructions for the new vents say to caulk from the base of the tube out one inch from the fixture. That's a lot of caulk, but I looked at a newer Airstream parked near me in our storage facility, and that's the way Airstream did it.

Lastly, I decided to use AdSeal for my sealant. I have two fresh, unopened tubes, and it's holding up really well on my 6-year old roof. Whatever they were using in 2006 didn't last long on my old Airstream as it was flaking away and had to be replaced in 2012, so I'm confident that AdSeal will do the job here.

I hope to finish this tomorrow.

Randy

[SilverCabin]

Well, I didn't get back to my project on Saturday as planned, but I finished today. Everything went smoothly.

I gave the area a quick wipe with denatured alcohol to ensure a clean surface for the AdSeal. Then I filled each of the old holes with the sealant and inserted a pop rivet. I then caulked over top of each rivet.

With the old holes filled, I caulked around the vent pipe, put the gasket in place, then screwed down the vent base. Set all the screws snug without distorting or cracking the base. The first photo shows the completion of these first two steps.

Following the instructions, I caulked from the base of the vent out about 1" from the edge. This covered all the old screws and places where I had scratched the roof paint. I then used a putty knife and a wet finger to tool the caulk to get a finished look. The second photo shows the vent installation after this step.

Lastly, after gluing the funnel into the vent top, the top is glued in place over the vent base. If Airstream had left the pipe a little longer, you wouldn't need the included funnel that directs any stray rain down the pipe into the tank. The pipe is an exact fit into the top. The final photo shows the complete installation.

BTW: This took about one half of a tube of AdSeal.

Thanks for following along,

Randy

[SilverCabin]

Two dry fittings are necessary to ensure the gasket is trimmed correctly and that the final installation of the top with the funnel glued in-place will be able to be installed on the vent base. The curved roof of the Airstream makes this necessary.

If you are going to reuse the gasket, put it in-place before you trim it to size. Then dry fit the base and top, with the funnel glued into the top (do not glue the top to the base yet), to the vent pipe. Mark the gasket where it needs to be trimmed, and then trim it to fit. If you try to eye-ball the alignment without the dry fit, it will be off slightly when installed.

Dry fit again when you are ready to drill the holes for the base. Put the gasket down, then set the base with the top attached but not yet glued to the base. The funnel when inserted into the pipe will align the base with the pipe. Holding the base in-place carefully remove the top and then punch the holes for the screws.

These dry fits will ensure that the gasket is fully under the vent base, and that when you set the top in place, and glue it to the base, the funnel will be in the pipe and the top will align with the base.

Randy