Thursday, February 2, 2023


“Dew” away with mildew in the RV!

By Chris Dougherty
Chris Dougherty is a certified RV technician. Here is a letter he received regarding mildew in an RV from a reader while he was serving as’s technical editor.

Dear Chris,
We live in Florida, where high humidity is always present. I try to keep our 25-foot Hi-Lo trailer lowered and covered during the winter months. We use a Damp Rid Large Room dehumidifier and run a 12-volt fan to circulate the air. Even with all this we still have musty smells when I check the condition of the Damp Rid container. I’ve had to remove the ADCO cover and raise the trailer to try and improve the inside condition. Any ideas? —George

Dear George,
Florida is a tough environment when it comes to humidity and mildew. Once mildew sets in it’s hard to get rid of.

Here are a few thoughts. First, I always look at soft goods like carpeting. Any of those will hold moisture, as will wood products. Have you had any leaks in the unit? Concealed moisture breeds mildew, and it can grow in the wood underneath the linoleum, or in the walls or ceiling. Check the outside seals carefully, and check for any rot on interior panels and surfaces. If you can’t find any rot, I would open the unit up and remove everything (on a nice day or two, of course) and spray every surface of the inside of the unit with a mildew removing solution, like a bleach and water mix in a spray bottle — just be careful about sensitive dyes and fabrics.

Lastly, keeping the unit closed up may be a contributor if the damp air is stagnant. I would consider some type of forced air ventilation that brings fresh air in and pushes old air out. I’m not certain that the chemical dehumidifier is of adequate strength to combat tropical moisture like this.

Practical Sailor did a test on a number of cleaners and mildew removers. One of the products they tested which I use every day, and did during most of my 23 years in emergency services, is Spray Nine. Home Depot and Lowe’s both sell it, and according to Practical Sailor, it is also good at removing mildew.

Editor’s Note: Spray Nine products are available at Amazon.



If you value what you learn from, would you please consider becoming a voluntary subscriber by pledging your support? Every contribution, no matter how modest, helps us serve you better. Thank youLearn more here.

Facebook Groups you might like
RVing with Dogs
RV Tech Tips
RV Advice
Towing Behind a Motorhome
RVing Over 70
. . . and the official Facebook page

Winterizing your RV this season? Amazon has a wide choice of RV antifreeze.


3.5 4 votes
Article Rating
Subscribe to comments
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
Andy Eippert
1 month ago

An RV tech, who is also a good friend, suggested I buy a dehumidifier to use in our coach as we snowbird in Florida. He showed us the model he uses and we found the same thing on Amazon. What a wonder it is – we are able to keep the humidity inside at 35%. I know they make dehumidifiers that will pump the collected water into a sink drain. If you have 110 available, wouldn’t that keep the humidity low enough to prevent that mildew odor?

Colin Simms
1 month ago

I live in Canada: Cold, snowy winters and a humid summer. I have been told NOT to cover an RV with anything. Moisture can’t escape and invites mold to form. Comments?
I would like to know the truth!

1 month ago

We live in Texas and have always stored our RV with vents open. Maxxair II covers work for us for ventilation while keeping rain out.

Carl W
1 month ago

Living in Florida, I would not be using a chemical form of dehumidification. If it is at all possible (electricity available) I would use a standard compressor dehumidifier set at around 45% or 50% relative humidity and find a way to run a hose to the outside so the bin doesn’t need to be emptied repeatedly (I’m not sure how to do this in a Hi-Lo that is lowered, but I have used a dehumidifier in my trailer, setting it on the counter and running the hose into the gray water tank. My gray water drain cap was replaced with one that has a molded hose connection so I ran a hose to nearby landscape plants and opened the gray water valve. Trailer stays dry and no hint of musty smells or mildew.

1 month ago
Reply to  Carl W

I do the same thing however being over 40 feet long I use 2 smaller dehumidifiers 1 in the rear bathroom and 1 in the kitchen area also a couple of fans to circulate the air. Always nice and dry and smelling good.

Subscribe to our newsletter

Every Saturday and Sunday morning. Serving RVers for more than 20 years.