After removing several black and grey tank roof vents during roof repairs, I noticed a common rusting problem with the screws mounting the vent cap to the roof. This problem has shown up across all 18 of the black and grey tank vents I have removed so far. I am not sure what year Sunline started using this style of tank/plumbing vent.
I am passing along the findings so when club members change their tank vents due to damage or are up on the roof caulking other areas, they can seal the vent in a better way to prevent this leak in the future.
This rusting screw issue may be a larger industry-wide issue. I know Jayco and Coachmen have used this vent, and both companies sealed them as Sunline did.
The tank/plumbing vent I am referring to is a Custom Plastics two-piece plumbing vent. The vent has a lower base to hold and seal off the vent pipe's sides and an upper cap with three mounting legs covering the open vent pipe. Here is the original manufacture, I do believe. Custom Plastics | Specialty (Select Roof Vents) They are an excellent vent cap; I have no issues with the vent itself; the problems come with how the installer seals the vent to the roof.
Here are some pictures to show problems. These two tank vents came off of different campers with extreme opposites in roof maintenance over the camper's life, yet the rusted screw issue displays the same mode of rusting.
This vent cap is on my 2004 T310SR I changed in 2019, which I have maintained the roof since 2007.
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In 2017 this vent cap was removed from my 2004 T1950 project camper, now in restoration. This camper did not have very much roof maintenance since it was new. I can tell the original caulk still existed in many areas with no touchups.
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The screw rusting leak mode was in the same place between those two extremes and the other 14 vents I have had off over the years.
Here is the problem as I see it happening. These pictures were from my T310SR when I changed the vents in 2019 as they started to become brittle. I know the caulking was still in good condition, yet the rusting screw issue still prevails.
The problem starts at the three screws that attach the vent cap through the vent base and then onto the roof circled in red. This picture shows how the water was getting to the screws even with good caulk on the perimeter, which was well maintained.
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Not every screw rusted the same; how much water collected in each location could be different. The top of this screw holding the cap and base in the red circle is not rusted at the head like the other two on the same vent. The other vents I removed over the years had similar patterns; some had all three screws heads rusted, others only one or two.
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The red arrows and circles point to the problem areas, which have no added sealant to prevent water from getting to the screw threads from the inside of the vent cap. Water collects and puddles in the gap between the vent cap's three legs in the red arrow area as the vent cap covers the vent base.
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The circles show the dirt witness trail the water followed to get to the screw threads.
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The screws removed in this picture are next to their corresponding holes. Two of the three screws that go through the cap and base have the most advanced corrosion. Once the screws start rusting at the exposed threads at the cap and base junction, the rust keeps migrating up and down the entire screw over time. In some cases, the wood in the roof supporting the screws was rotted, not leaving screw clamping pressure to the cap.
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What is missing is sealant on the backside of the vent cap legs at the screw locations, like this. Here is the fix if you are not removing the vent. Clean the area and caulk with Dicor lap sealant. You can do more if removing the vent. (See the next reply in this post.)
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The simple lack of caulking behind the vent cap legs is the problem. There are no directions that come with these vents on how to seal them, and the issue may still be ongoing today on new campers. I never realized this issue until enough of them keep coming up with rusted screws; there is a repeating problem. Some of the screws in the pictures above have rust only at the tip of the screws; this I feel is from attic moisture rusting from the tip of the screw upward. The 1” long screw hangs below the 1/2" OSB reinforcing pad used on the Sunbline rubber roofs exposing the screw end to the attic environment. This vent is next to the shower steam dome, a general area that allows moisture to enter the attic.
Here is a vent cap off one of my good friends Jayco. You can see there is no caulk behind the vent cap legs.
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If you are looking for replacement vent caps of this style, here is where I have found them to be cheaper. The cost on the web is all over the map. Free shipping also differs. I have also noticed the patent may have run out on this vent, as other brands are for sale with very slight tweaks in the molding process.
I have used RV Upgrades in the past and had a positive transaction.
https://www.rvupgradestore.com/Custo...-p/22-0516.htm
I will add a second reply with the “how-to” remove and install a new vent for those who have not been through this before. These plastic vents do not last forever; sun damage makes them brittle.
Hope this helps
John
For more pics on the tank vents, see my Flickr page here https://www.flickr.com/photos/camper...57717746807667
I am passing along the findings so when club members change their tank vents due to damage or are up on the roof caulking other areas, they can seal the vent in a better way to prevent this leak in the future.
This rusting screw issue may be a larger industry-wide issue. I know Jayco and Coachmen have used this vent, and both companies sealed them as Sunline did.
The tank/plumbing vent I am referring to is a Custom Plastics two-piece plumbing vent. The vent has a lower base to hold and seal off the vent pipe's sides and an upper cap with three mounting legs covering the open vent pipe. Here is the original manufacture, I do believe. Custom Plastics | Specialty (Select Roof Vents) They are an excellent vent cap; I have no issues with the vent itself; the problems come with how the installer seals the vent to the roof.
Here are some pictures to show problems. These two tank vents came off of different campers with extreme opposites in roof maintenance over the camper's life, yet the rusted screw issue displays the same mode of rusting.
This vent cap is on my 2004 T310SR I changed in 2019, which I have maintained the roof since 2007.
In 2017 this vent cap was removed from my 2004 T1950 project camper, now in restoration. This camper did not have very much roof maintenance since it was new. I can tell the original caulk still existed in many areas with no touchups.
The screw rusting leak mode was in the same place between those two extremes and the other 14 vents I have had off over the years.
Here is the problem as I see it happening. These pictures were from my T310SR when I changed the vents in 2019 as they started to become brittle. I know the caulking was still in good condition, yet the rusting screw issue still prevails.
The problem starts at the three screws that attach the vent cap through the vent base and then onto the roof circled in red. This picture shows how the water was getting to the screws even with good caulk on the perimeter, which was well maintained.
Not every screw rusted the same; how much water collected in each location could be different. The top of this screw holding the cap and base in the red circle is not rusted at the head like the other two on the same vent. The other vents I removed over the years had similar patterns; some had all three screws heads rusted, others only one or two.
The red arrows and circles point to the problem areas, which have no added sealant to prevent water from getting to the screw threads from the inside of the vent cap. Water collects and puddles in the gap between the vent cap's three legs in the red arrow area as the vent cap covers the vent base.
The circles show the dirt witness trail the water followed to get to the screw threads.
The screws removed in this picture are next to their corresponding holes. Two of the three screws that go through the cap and base have the most advanced corrosion. Once the screws start rusting at the exposed threads at the cap and base junction, the rust keeps migrating up and down the entire screw over time. In some cases, the wood in the roof supporting the screws was rotted, not leaving screw clamping pressure to the cap.
What is missing is sealant on the backside of the vent cap legs at the screw locations, like this. Here is the fix if you are not removing the vent. Clean the area and caulk with Dicor lap sealant. You can do more if removing the vent. (See the next reply in this post.)
The simple lack of caulking behind the vent cap legs is the problem. There are no directions that come with these vents on how to seal them, and the issue may still be ongoing today on new campers. I never realized this issue until enough of them keep coming up with rusted screws; there is a repeating problem. Some of the screws in the pictures above have rust only at the tip of the screws; this I feel is from attic moisture rusting from the tip of the screw upward. The 1” long screw hangs below the 1/2" OSB reinforcing pad used on the Sunbline rubber roofs exposing the screw end to the attic environment. This vent is next to the shower steam dome, a general area that allows moisture to enter the attic.
Here is a vent cap off one of my good friends Jayco. You can see there is no caulk behind the vent cap legs.
If you are looking for replacement vent caps of this style, here is where I have found them to be cheaper. The cost on the web is all over the map. Free shipping also differs. I have also noticed the patent may have run out on this vent, as other brands are for sale with very slight tweaks in the molding process.
I have used RV Upgrades in the past and had a positive transaction.
https://www.rvupgradestore.com/Custo...-p/22-0516.htm
I will add a second reply with the “how-to” remove and install a new vent for those who have not been through this before. These plastic vents do not last forever; sun damage makes them brittle.
Hope this helps
John
For more pics on the tank vents, see my Flickr page here https://www.flickr.com/photos/camper...57717746807667