Everything You Need to Know About The RV Plumbing Vent Cap

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Your RV plumbing vent cap is one of the RV accessories that isn’t often thought of, but its everyday function is an important one. It helps the entire RV plumbing system work effectively, and most importantly for those inside your motorhome, it helps displace odors coming from your gray and black water tanks.

The RV plumbing vent is a pipe that runs upward from the top of the two water tanks to the roof of your RV, where the odors can be vented out. If your RV plumbing vents cap gets damaged or lost, you’ll notice it – quickly. And this is a problem you’ll want to take care of as soon as possible. Luckily, replacing an RV plumbing vent cap is a quick and easy DIY task you can do yourself.

First, you’ll want to purchase a replacement plumbing vent cap. You can find one at most RV or camping stores or online at Amazon.com and other sites. You’ll want to make sure the cap you purchase will fit on the existing vent pipe. Once you get the vent cover, you’ll want to gather the rest of the necessary tools. These include:

  • A dry rag and paper towels
  • Screwdriver
  • Putty knife
  • Drill gun or electric screwdrivers
  • Sealant (make sure this is safe for your RV!) and caulk gun
  • Mineral spirits for cleaning

Keep in mind that regular household caulk is typically not safe for your RV. Read your owner’s manual if you’re unsure, but typically rubber, aluminum or fiberglass is safe to use on your motorhome.

Next, remove your damaged RV plumbing vent cap. If it’s missing, you can skip this step! Start by prying up the old sealant surrounding the cover using a putty knife or screwdriver. You’ll want to also ensure you’re removing sealant from the screws also, as the screws need to be removed. You can loosen those with your drill gun and then lift off the entire vent cap.

There will likely be remaining sealant, so you’ll want to continue to use the putty knife to remove it. Once you’ve removed all you can, you can use mineral spirits and paper towel to scrub some of it away and clean the RV plumbing vent pipe itself. Once it’s as clean as you can get it, use the dry rug to give it a final scrub, removing remaining mineral spirits and excess debris.

After that, you’ve earned a break! Give yourself a half hour before continuing the project, so that the roof can dry and the cleaning product is completely gone before you place the new RV plumbing vent cap. Once everything is spic and span and dry, you can fit your new cap on the sewer vent pipe. Start by setting the vent cap in place to see where you’ll need to use sealant for bonding.

When you place the vent cap, don’t be concerned if the screw holes from the old vent cap don’t line up. You can drill new holes if needed and cover the old holes that don’t line up with sealant. Once you’ve noted where you’ll need to use sealant, you can remove the vent cap and use the caulk gun to put a first layer of sealant around the pipe in a circle. Place the sealant right where the new RV plumbing vent cap will lay and be generous! You’d rather have too much sealant than too little.

While placing the sealant, you’ll also want to make sure that it covers any existing screw holes. Once all the sealant is in place, while it’s still wet, place the new RV plumbing vent cap down, wiggle in place and apply firm, steady pressure for a few minutes to ensure it bonds to the sealant.

Next, you’ll want to finish by placing the screws, which ensure the cap is well secured to your RV roof. If the holes from the previous cap didn’t line up perfectly, you’ll need to drill new holes. Once the holes are drilled and screws are placed, you’ll want to add another layer of sealant over each of the screw head and one final layer over everything to add one final protection against leaks.

When using the sealant, try your best to make it a thin, even layer, but don’t stress too much if it’s not perfect. As the sealant dries, gravity helps to thin it out and make it even. For the final step, screw on the upper portion of the RV plumbing vent cap and that’s it! You’re done and your RV is protected against bathroom odors making their way into your living space.

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