Here is a picture of “how-to” remove and install your tank vents.
Most Sunline roofs are not a direct walk-on roof. When servicing items on the rooftop, precautions need to be in place to prevent damage to the roof system or you falling through it. Start with putting a canvas or other protective material over the rooftop to stop abrasion.
Using a sturdy ladder, reach from the side, place manageable sized plywood pieces onto the tarp to spread your weight out over a larger area. 3/8” or thicker plywood 24 – 30” wide by 48” long works well.
Feel the roof for the stiffness of the rafter locations that are under the rubber or metal membrane. Place the plywood over a minimum of two rafters to support the single sheet of plywood. Take care getting on and off the ladder. Crawl around on your hands and knees while working on the roof helps also.
Using a heat gun, gently warm the old sealant, use a metal putty knife with all blade end edges dulled/rounded up, and scrape up the old caulk.
Remove the six screws.
Warm the lower base of the vent to soften the butyl tape. Gently work the putty knife under the base flange. Take care not to dig the roof. Lift the old cap and base off the roof.
Gentle heat and scrape what you can to get the old sealant and butyl off the roof.
With nytril gloves on, use mineral spirits on a rag and wipe the area clean. Do not pour a cleaner on the roof; only apply with a rag. Rubber roofs are affected by these cleaners when left for a long time. You can scrub. Wipe the roof dry as soon as you have completed the mineral spirits cleaning. Follow with a high flash cleaner, Naphta, denatured alcohol, lacquer thinner, etc., on a rag and wipe clean and dry the entire vent area. The high fash cleaner will remove leftover residue from the mineral spirits and dry quickly.
Prepare the new tank vent base with high-quality butyl tape. Tape 1” wide x 1/8” thick works well. Here is the brand I use and where I buy it. GSSI MB-10A butyl tape https://www.bestmaterials.com/detail.aspx?ID=19987
Other steel building or roofing supply places sell other good brands as well. I caution to “not” buy butyl tape from Amazon. I have had too many unusable rolls shipped by their packing process.
Clean the base and top of the mounting flange with the high flash cleaner. Place the butyl tape on and fold/bend it to a circle making pleats as you go. Do not stretch it; it will thin. Leave the release paper on until you are ready to install.
Apply three strips to the places the vent cap will mount.
After the butyl tape is on, hand wipe 303 UV Protectant on a rag inside and outside of the vent base and cap, wipe on thin, and wipe until dry. This product https://www.goldeagle.com/product/30...ve-protectant/
You can get it at the auto store or retailers. This protection will extend the life of all plastic and rubber roof items. I apply 3 to 4 times a year after cleaning the roof. Inside the vent will only get the initial treatment.
I install a plastic window screen over the vent pipe to keep insects and spiders from nesting. Cut the screen large enough to cover the pipe. The screen will collapse over the pipe. Test fit if needed before removing the release paper on the vent base.
Remove the release paper from the vent base, and warm the butyl with the heat gun. Align the screw holes in the vent base to the roof holes. An ice pick helps. Press base over the pipe holding the screen until the vent base starts going over the pipe.
Using stainless or coated steel, no. 8 x 1” long screws, install only the three base screws that do not hold the vent cap down. Warm the vent flange. You can use a drill driver to start the screws, but stop short and tighten by hand. The butyl will ooze, and that is OK.
Remove the release paper from the three cover butyl tabs.
Align the vent cap leg holes with the base holes and install the cap. An ice pick aligns the holes quickly.
Warm the cap legs butyl and install the 3, #8 x 1” lg. screws. Drill driver OK but stop short and tighten by hand. Butyl will ooze.
Using a plastic scraper with a rounded edge, trim the excess butyl off the roof and base. Take care not to dig the roof.
The vent cap should look like this with the butyl sealing the gap, where water can leak in.
Using Dicor 502LSW or 501LSW self-leveling lap sealant, https://www.rvupgradestore.com/Dicor...-p/38-8896.htm
Seal over the top of the butyl inside the cap legs as shown.
Continue applying the sealant over the vent base and screws.
Note: Sunline used 1 1/2" ABS sch 40 pipe vents on the black tanks, and on “some” grey tanks, they used 1 1/4” ABS sch 40 pipe.
The 1 1/2" measures approximately 1 7/8” across the hole.
The 1 1/4" measures approximately 1 5/8” across the hole.
There are different part numbers of tank vents for the various pipe sizes to make a good tight fit between the vent base to the pipe. I have not yet found the 1 1/4" tank vent for sale that Sunline used, but I found a workaround. At the local lumber yard/hardware store, buy an ABS plastic 1 1/2 to 1 1/4 reducing bushing. They cost about $0.60 or did the last time I bought some.
The bushing creates an excellent tight fit. You do not have solvent weld the fitting on, only press it on. There is no air pressure on this vent pipe, and the bushing can not go down or up to come off the pipe as the vent base traps it in location. The insect screen will still work with the fitting. You may have to trim the vent pipe to compensate for the added bushing to allow the base to sit flat. “Check” the pipe height “before” installing the vent base.
The 1 1/2" tank vents are advertised on some websites to work on both sizes, but I do not like the big gap between the pipe and the vent base using a 1 1/2 base on a 1 1/4 pipe. Get the adapter bushing. If the top cap cracks off, and it will in time, that gap exposed at the base will leak into the roof as there is no tight fit to the pipe.
I hope this helps.
For more pics on the tank vents, see my Flickr page here https://www.flickr.com/photos/camper...57717746807667