Be sure to sign up for the weekly RV Travel Newsletter, published continuously every Saturday since 2001. Click here.

Thursday, April 26, 2012

Water is Evil. How to Find and Fix RV Vent Leaks - Part.1

This week I am going to be taking a look at how to fix 14" x 14" vent leaks. Not that I wanted to look at that, mind you, but it appears that Murphy (who was, as we know, an optimist) decided it was the thing to do. Yay!

Here's the situation:
Vanity Sink Fluorescent Light Removed
I was going about my regular de-winterization routine when we decided it would be a good idea to clean the vent fans and inside of the domes. Seemed like a great idea! Especially after the Stinkbug Invasion of last year. There was some NASTY bug bits left over from the fight. Well, after they were all cleaned up we did a few more housekeeping tasks and called it quits for the day. That night we had a heavy rain. The next day I went down to continue the work inside (it was still raining) and found a VERY wet trail leading to a saturated headliner area. In my RV the whole inner ceiling is carpeted. It's quite nice, Velcro sticks to it like crazy! Well the roof is slightly curved so water will drain off the top. That's a good thing. Although it will also drain from a leak in the vent in between the fiberglass roof and the wood and foam sandwich below all the way to the edge. In this case it was pooling near the vanity sink overhead fluorescent light.

Roof Curvature
 I dried everything as best I could and scrambled up on the roof with some trash bags and painter's blue tape. After taping the bag over the vents and seams I realized tape doesn't stick so well to wet fiberglass. Back down for a towel and back up to fix the problem. Not knowing whether the leak was patched (or something much worse was going on...the mind tends to go to the worst scenarios!) I went back inside and stayed for a while to keep an eye on it. After an hour I went back up to the house and called it a day.

Temporary Leak Fix
Here we are 5 days later and it looks as if there has been no additional water seeping in. The ceiling seems dry and what I can see of the inner roof structure is dry. The temporary fix worked!

Now we have to fix it correctly.

Since I have no idea where the leak is actually coming from, it could be the screws in the vent flanges, the caulk around and under the flange, the edge of the roof, the right thing to do would be removing the entire vent, cleaning everything and re-installing the vent properly. That's a much bigger job than I want to tackle at the beginning of the season! Who knows what evil lurks underneath! Better to start that job AFTER the end of the season. I know, you should always do it the right way to avoid problems down the road. I say it enough myself. I guess I'm just a bit antsy to get RV'ing!

Here's what I will try:

I purchased some bonding tape a 4" x 50-foot roll that has had great reviews as a seam sealer and leak fixer. I will take out all the screws and clean the top of the vent flanges of all the lumpy caulk and previous repairs. Once it's mostly flat I will put some NON-Silicone sealer in the screw holes and re-install the screws. Once finished I will carefully place four pieces of the tape (one on each edge) to cover the flanges all the way up to the vent itself. I will press down the tape until I get the air bubbles out and it is uniformly adhered to everything. Then I will cross my fingers and hope it works!

Shower Skylight
I'm thinking about filling any air gaps (from the inside) with expanding foam. Not sure that's wise...but I will look into it. I've also discovered a small crack in my bathroom shower skylight. Of course it is a non-standard shape and size. So far I haven't been able to find a replacement and I am not sure a regular dome will clear the luggage rack on the roof.

Next Week, you'll see the job being done and the results. Stay Tuned!

Be Seeing You...Down The Road,

Rich "Wanderman"

See Part 2: Click Here!


  1. Yeah, roof vent leaks suck.

    My last one, I tore the entire roof vent assembly off and removed the layers of alternating henry's asphalt patch and snow roof that was up there from previous owners till I got down to bare aluminum.

    I then used Trimetric caulk (I think that's the name of the stuff, really thick sticky caulk) on the base of the new vent assembly to glue down the new vent, after which I coated all the edges and screws with Dicor self leveling caulk, over which I rebuilt the roof level back up a 1/8" of an inch with layers of snow roof with over lapping layers of fiberglass mesh embedded in it.

    Hasn't leaked since.

    Now, what I'd recommend is if you still have the inside part of the vent assembly down, treat the wood (once dry) inside with winwax wood hardener to prevent it from being susceptible to future water penetration.

    Now, off subject, but what style is your vanity fluorescent light fixture?

    I'm still perusing for a used round tube style fixture for my kitchen (I went to twin tube fixture in my dinette area and I love how much light I have now for less amperage than my previous two wedge bulbs consumed) .

    1. Big Matt,
      This leak(s) I have opted to patch until the end of the season when I will likely pull both vents and fans and start again. I am leaning toward the Eternabond style tape kits with some expanding foam patches. Still researching that.

      The vanity light fixture is a thinlite 2 tube T8F15 2 bulb assemble. My side switch is squeezed against the wall, so there is an identical on/off switch on the face of the vanity itself. It has a "pebble" style translucent cover and works quite well. I put a couple of LED strips (Warm White)in there and another switch to select them. Works well and looks good. of course you always look terrible under fluorescent light, especially in the morning! Maybe it's just me!

      Rich "The Wanderman"

    2. Thanks Rich, I have the twin T8F15 fixtures, trying to locate a used circline fixture to use in the kitchen area vs another twin straight tube. Most of the thin-lite ones are round 9" tubes which only put out around a 1000 lumens, so I'm watching to see if I can catch another 12" unit similar to their more expensive model to instead which puts out 1800 lumens.

    3. Big Matt,
      I added LED Warm White strips to both my 12" fluorescent fixtures and the other two, longer ones. The strips actually produce more lumens than the fluorescent tubes at an even lower power draw.

      The vanity fixture is a two tube just like yours.

      Look for the SMD5050 style. You wouldn't need to find new fixtures, you can adhere these almost anyplace you can get power to and they generate very little heat.

      Rich "The Wanderman"

    4. Thanks, I'm still waiting on them to solve the directionality of the LED bulbs that they currently suffer from, most are maxing out at 120 degree light output range, which isn't bad, but still less than 360 degrees of a standard fluorescent tube.

      I do have a couple LED bulbs, I used one as a replacement in a fixture above my sink and it puts out a decent light level, but it's also twice the size of the original blub that was in there, I ended up having to redesign the contact assembly for the base so that the bulb could sit more horizontally in the fixture (base from the original incandescent bulb was angled down to hold the blub away from the reflector) so that I could put the cover back on.

    5. Big Matt,
      Take a look at the newer technology LED bulbs, the output levels are MUCH higher for a given size. All my replacements closely match the original size and output a similar amount of lumens. The tube style fluorescent wastes a lot of output into the white reflector. better to have more directional may be better. it was in mine.

      Rich "The Wanderman"

    6. Hmm... mine doesn't have a white reflector, rather a polish aluminum back plate, granted they're old McLean Industries fixtures from the 80s vs Thinlite units that have painted steel bodies.

      I have been looking at the newer LED bulbs, but haven't found an attractive looking replacement that produce a higher lumen output to the wedge base bulbs that were in my original fixtures (Crystal clear plastic that's formed into a magnifier lens, which when I tried to do a scuff job on to make them somewhat opaque, cracked), looking for 820 - 1000 lumens per bulb.

    7. Hmmmm.....I'll look around...

      Rich "The Wanderman"

  2. We had just purchased a new (used) trailer and after cleaning the roof off, we developed a vent leak. The funny thing is, even though the water was coming in the vent the leak was not actually around the vent, it was at the end seam and leaking back. Eternabond worked like a charm. We removed all the previous silicone the old owner slopped on the roof and sealed everything with the tape. It is very easy to use and sealed great, no more problems.

    1. Glad to hear another bonding tape miracle! You are absolutely right about the MUST of removing all silicone. It won't adhere to it at all. When will people learn, slopping more goop over a leak won't always work, but will always make a mess!

      Rich "The Wanderman"

  3. I say it enough myself. I guess I'm just a bit antsy to get RV'ing!

    1. FRC,
      I know EXACTLY how you feel!

      Rich "The Wanderman"


Thank you for your comment. Our moderator checks each one to make sure we keep the Spammers away. So the comment will not appear immediately.