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Old 09-10-2017, 12:47 PM   #1
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Seattle206's Avatar
2018 22' Sport
Bellevue , Washington
Join Date: Aug 2017
Posts: 21
Winterizing in the Pacific Northwest

We're new to AS life having just purchased a 2018 Sport 22 FB. Two questions: what do others recommend to prevent mold and moisture inside the AS during winter storage outdoors in Seattle? The climate is pretty mild here with occasional temps below freezing, should we winterize or will keeping a heater on during cold snaps keep valves and lines from freezing? Thanks

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Old 09-10-2017, 01:28 PM   #2
Half a Rivet Short
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 6,763

How certain are you that it will never go below freezing 4 to 5 months from now? Heat is fine for some parts of the trailer and pretty much useless for other parts. Best bet is to get a (cheap) jug of RV antifreeze and spend an afternoon learning the procedure to put it in use.

Moisture wise, you can get pails of chemical dehumidifier "stuff". Amazon is one source, there are lots of others. It conveniently changes colors as it gets wet. Check the buckets once a month. Run the stuff through the oven if you need to. It's not very expensive (pound for pound cheaper than some of the gizmos that just have it in a cute package).

Heat is not a bad idea. Indoor / covered storage is also a good idea. I'd suggest asking around to see what's available.

Other things to consider: Cover the tires, it will help them a bit. Pull the batteries and / or put them on a trickle charger. Pull as much as you can out of the trailer and store it in the warm and dry. Don't go crazy, but don't store the cookie inventory in the trailer either. Ant bait and mouse "stuff" might also be a good idea.

Lots of options.


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Old 09-10-2017, 01:52 PM   #3
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2018 19' Flying Cloud
Coeur d Alene , Idaho
Join Date: Dec 2015
Posts: 234
You might consider scattering some moth balls around underneath. I've been told that helps deter the mice from coming around. We've been doing that for our boat and some other vehicles during the winter and so far it seems to be helping.
Dale & Jane

2018 Flying Cloud 19
2003 Dodge Ram 2500 Quad Cab Diesel
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Old 09-10-2017, 01:55 PM   #4
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Byron Center , Michigan
Join Date: Aug 2017
Posts: 275
You mention putting a heater in the trailer. That tells me that you might have access to 24/7 shore power where you store your trailer. Is a dehumidifier an option for you to help control moisture and mold?
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Old 09-10-2017, 02:17 PM   #5
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2018 28' International
Renton , Washington
Join Date: Sep 2016
Posts: 281
Even here, winterizing is a must. Last winter saw several periods of sub freezing temps. We use ours throughout the winter and have to winterize at the end of each trip. Even with that I forgot the outdoor shower once and cracked the diverter. Low point water lines won't be protected from an inside heater.

If left for more than a month without shore power, remove the batteries or put on a trickle charger. If hooked to shore power confirm your power converter is a multistage unit that won't overcook the batteries.

You might consider installing vent covers like Max Air or similar so you can leave your vents cracked for moisture control along with dehumidifiers. Then in the spring just count on a thorough washing to remove the exterior sediments and crud we get in the NW.
2018 28 International Serenity
2013 F150 Ecoboost
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Old 09-11-2017, 08:56 AM   #6
Half a Rivet Short
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 6,763

Ok, dehumidifiers, there are two basic types:

One is a refrigeration system that collects water in a bucket. Running one will pile up water that needs to be emptied somehow. Combine that with freezing temperatures and it gets complex.

The second kind is absorptive chemicals. You dry them out by heating them up. The absorbed moisture dumps out into the area you heat them up in. They then absorb a finite amount of moisture and stop working until dried out again. Volume matters with this stuff. Bigger is better. A 5 gallon pail will last longer than a three ounce wall mount.

Either way, there is a maintenance process. If moist air can get into the area, that probably will be needed more often than in a sealed box.

So, no magic, no miracles.

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Old 09-11-2017, 11:39 AM   #7
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2010 25' FB Flying Cloud
Snoqualmie , Washington
Join Date: Nov 2014
Posts: 144
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We have had our 25' AS a few years up here in the PNW and have not winterized with exception of throwing some anitfreeze in the toilet, shower, and sinks; and have a little portable heater we turn on when it gets cold out. No problems and allows us to use it at the spur of the moment for guests, etc. I also went to one of the Airstream dealers owners meeting here in Covington our first winter, and asked the head Service guy whether it was necessary to winterize - and he said up here in the PNW you shouldn't have too. I find you do need to wash it a few times during the winter to keep the green stuff from collecting.
Note: I also have 5 small digital thermostats that save the low temperature - and i place them strategically around the AS just to keep an eye on the temp when we get real cold spells.
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Old 09-11-2017, 12:22 PM   #8
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2008 23' Safari SE
White Rock , British Columbia
Join Date: May 2007
Posts: 24
Hi there,
We are a 100 miles or so north Seattle, so am familiar with the temperatures and moisture of the area. Here is the process I have followed for the last 10 years. Following the instructions in Schu's News. My version:
  • Drain and flush tanks. (Black, grey and hot water).
  • Open low point drains and let them empty. While this is happening open all hot and cold faucets inside and outside (shower). Once complete close all taps and low point drains.
  • Blow out the water lines. (I think this is the key and most important step). I bought a small air-driven construction compressor (not oil!). Then using a series of fittings, I made a valve controlled adapter to thread onto the city (water) inlet on the trailer. Once the hose is attached, valve closed, set compressor to about 50PSI, when ready I open the valve to pressurize the system in the trailer. One by one I open and close each hot and cold water tap, water filter, inside shower, outside shower and toilet. I carefully pre-release (partially unscrew) the water tank plug, (before the system is pressurized), then carefully remove and blow out the tank. Open and close the low point drains again. Once I have done that once, I start again and do that sequence until all you get is hissing air out of each faucet.
  • I personally have never put RV antifreeze in the water lines. Thats a personal choice as I don’t want any residual flavor from the antifreeze in next years water. Hence I am very thorough and patient in the blowing out the lines step.
  • I do pour antifreeze into all the traps, as well grey and black tanks. A few cups of antifreeze into one of the sink drains (I hope 2 cups or so gets into my grey water tank). Then into each of the other drains I pour a cup or so to seal the traps. I also pour about 2 cups into the black water tank and make sure there is a couple inches of antifreeze on the closed toilet seal. Close or cap the sink drains to prevent evaporation, close toilet lid (check back a couple times over the winter in case you need to add a bit more to the toilet seal).
  • Place a towel under the water filter, remove filter, store in the house or garage until next season.
  • For moisture control I use what boaters up here use–called “Dri-Z-Air”. So far in my 23 footer I use two of these and check them throughout the winter. Empty and refill as necessary.
  • I do have access to electricity - so I run a heater at low output to just keep the trailer a few degrees above freezing when its really cold. Again checking to see if I need to bump it up or down throughout the winter. I use an oil filled heater (from Home Depot) for this task. I realize I am not heating the tanks or lines with this hence my thoroughness in blowing out the lines. The heater is likely not entirely necessary, but I have power so I figure why not.
  • I remove the batteries, fully charge them and store in my garage (off the concrete floor). Check them monthly and charge as required.

So… knock on wood - this method has kept our AS dry, mold free, and functioning perfectly for 10 years now! I have attached a link to the article I have in front of me one cold afternoon every November (or so!). He also outlines the steps for adding antifreeze to your lines if desired.
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Old 09-11-2017, 01:35 PM   #9
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1985 25' Sovereign
Olympia , Washington
Join Date: Dec 2005
Posts: 45
Welcome to the forum, and thanks for inviting us to address this timely subject.

Seattle weather is similar to that in Olympia where we live. Our Airstream went through a local freeze followed by several cold days on one occasion. Consequently, our Airstream will be winterized when stored during coldest months; it is an inexpensive insurance. Some retailers will tell us that winterizing is not necessary – it helps to keep their service departments busy.

To manage moisture and its effects, I find the following to be very satisfactory over the past 20+ years. The listed products are well described on Amazon, but may be obtained elsewhere (Airstream Seattle is aware of #1 & #2).
(1) Open all cabinet doors and drawers, and allow fresh air to circulate throughout the rig. Air is exchanged through two fantastic vents opened one inch each. Both vents are covered additionally with MaxxAir rain covers.
(2) Two 9” H2Out Space Dryer dehumidifiers (SD309) placed in saucers on the floor where they gather dampness from the heavy air settled there.
(3) Our rig always smells fresh through use of zeolite rechargeable crystal packs strategically placed throughout the rig.

Happy travels , Jim
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Old 09-11-2017, 05:32 PM   #10
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2016 25' Flying Cloud
Friday Harbor , Washington
Join Date: Jun 2016
Posts: 62
From the Washington San Juan Islands

This being my first AS, a FC 25, 2016, and first winter (just passed), I worried leaving it after the first week of January only putting antifreeze in the drains, some in the gray and black water tanks, and turning off the water to the AS. Attached as it is to shore power, I had two space heaters on low enough to keep (I hoped) everything from freezing. I opened everything I could open inside. In Costa Rica until middle Feb, I worried continually. There were some unusually cold stretches (I am told mid to lower 20s). I returned to find everything OK. I end with one question: I asked the Covington service guy if there is one low water point to open so as to drain the whole system. He said there was a 'cock' low on the water heater; open that and all water will drain. I didn't do it. True?
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Old 09-11-2017, 05:39 PM   #11
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2016 25' Flying Cloud
Friday Harbor , Washington
Join Date: Jun 2016
Posts: 62
Hi, if you see my San Juan Island reply, I am saying (with worry) basically don't fuss with anything in the coastal NW. The temp did get into the low 20s. How nothing broke still surprises me.
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Old 09-12-2017, 01:58 AM   #12
4 Rivet Member
2017 27' International
Fall City , Washington
Join Date: Aug 2013
Posts: 349
Winterizing in the Pacific Northwest

I am outside of Seattle about 1000 ft elevation. Heavy Metal's list is what I follow plus one more step: I "bleed out" the excess water in the fresh water electric pump (basically disconnect the line and run the pump for 20 seconds to purge water in the pump which can freeze and split a water line).In the PNW we sometimes get winters where nighttime temps dip in the teens. Mine is now stored indoors where I can run a shop heater but when it was outdoors I always air bled the water lines and followed Heavy Metal's process. Takes less than an hour and piece of mind is worth it. I never used antifreeze in the water lines either, just in the traps.
2014 28' Flying Cloud
2013 Ram 2500 Laramie Crew Cab CTD 4x4
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Old 09-12-2017, 05:14 AM   #13
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2014 20' Flying Cloud
Long Island , New York
Join Date: Jun 2015
Posts: 10,682
In addition to the good advice so far, we use these low wattage plug in Dampp Chasers under the bed and in the bath :
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Old 09-12-2017, 09:07 AM   #14
Half a Rivet Short
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 6,763

There are a lot of interesting water trap points on any RV. One approach is to open all the drains and faucets before you leave the last campsite of the season. Rumble down the road with everything open on the trip home. I've run into multiple people who recommend it.


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