Monday, September 25, 2023


RV Doctor: How to winterize an RV using a “Schrader valve”

Dear Gary,
I have been hearing about dry winterizing a motorhome using a “Schrader valve” and blowing the water out using an air compressor set on 20-PSI, plus putting some of the pink stuff in the kitchen sink, bath sink and shower drains only. Is this a good idea? If so, how do I find the Schrader valve and where do I install one? —Bobbie V.

Dear Bobbie,
The device you are seeking that incorporates a Schrader valve is called a blowout plug. It has the air inlet valve (Schrader valve) on one end and a male hose fitting on the other end. Mine is made out of milled aluminum, but I’ve seen brass blowout plugs as well as inexpensive plastic blowout plugs. I do recommend the metallic type.

The blowout plug attaches directly to the city water inlet hose connection, but only temporarily; it isn’t a permanent installation. Clean compressed air is then forced into the system to expel the water through the faucets and low point drain locations. It’s the quickest way to rid the fresh water system of water. Professional shops use them all the time while performing winterizing procedures or when an RV is going to be stored for any length of time.

blowout plug RV Doc 765

As you drain the fresh water tank and water heater, attach the blowout plug to the city water inlet. Open all faucets plus the hot and cold low level drain valves and then inject clean air. You can certainly apply more than 20-PSI since the entire piping system is pressure-tested at 80-PSI at the factory. And since all the faucets and valves will be open, it will be safe and quicker to use 80-PSI. Be sure it is clean air! Like I tell my seminar attendees, this is your fresh water system! Avoid using gas/filling station air or any air from a compressor equipped with a tank. The chance of contamination is greater if the compressor has a storage tank.

In addition, pour 1/4 cup of RV antifreeze down each drain to fill the P-traps, and you should be set for winter or any period of non-use.

gary-736You can purchase a blowout plug at any RV dealer or service center’s parts and accessories department and many websites online, including

Read more from Gary Bunzer at the See Gary’s videos about RV repair and maintenance.



  1. What about the water pump? In 50 years of winterizing RV’s I have yet to get enough water out of the water pump with compressed air to keep one from freezing in Kansas. I either have to use a RV antifreeze siphon tube at the pump to suck the pink stuff into the pump or remove the pump and store in the house.

  2. ” or any air from a compressor equipped with a tank” ??? Where do you get enough 80 psi air for the procedure if the compressor doesn’t have a tank?

  3. Schrader valve adapter: way too little volume to move water effectively. Use a brass direct compressor quickrelease plug with the largest aperture possible (drill out as wide as possible). Set pressure at 40psi before connecting.

    Contamination: use a $1 inline filter. Done? I use a commercial OILED compressor, but use a filter on all my air 24/7 – even pneumatic tools get filtered and dried air before I reinject oil…

    AF drains: I used to dump trap water and add AF; now I shop vac traps and add much less AF.

    Here’s a video of the whole process of air into AF winterizing. 10 minutes and $1 (1/2 gallon) of AF does my 35′ Jayco.

  4. I have used compressed CO2 from a tank. It will also do the job. Been told should still put pressure regulator inline so not to bust anything with too high of pressure.

  5. Whoa up guys. After you blow out all the faucets, your not done yet. There is still water in the ice maker line, dish washer, and washing machine. I cycle the ice maker to force it to take in “water” but there is now air in the line. You just need to cycle it until you hear air feed into it instead of water. You will have to dig up the info on your unit to find out how to force the cycle.
    The dish washer is much the same but after blowing in air, vacuum up any remaining water in the bottom. Then add some pink stuff to the bottom as you can’t get it all out of the sump.
    I don’t have a washer/dryer, but the procedure would be similar to the dishwasher.

  6. Be careful of the type of air compressor that you use. There are oil air-compressors and oil-less air-compressors. Oil air-compressors use oil to keep the crank shaft and piston lubricated like in a car. Oil can get by into the air lines and some insert oil into the lines, as many air tools require oil lubrication thru the air line. There is very little oil so it may not be noticed. Oil-less compressors do not have a piston, per se, but have a rubber diaphragm to compress the air, thus the air being cleaner. There are many oil-less compressors, even for air tools. Oil-less compressors are sometimes used in beverage machines to force the coffee thru the coffee grounds and filter. This is the way older vending machines used to work. Anyway, out of caution, I use my oil-less compressor to blow out my RV lines.

  7. I always use my portable air compressor for this job. Never gave the “contamination” issue a thought. But, I always drain my compressor when I’m done using it (for whatever reason), including that plug at the bottom that I assume (uh oh, there’s that word!) is to clear out any condensation left in the tank. That plug is always open until the next use.

  8. I blow out my lines but it’s hard to get all the water out. I blow them out and then I wait a day or two and do it again. My rationale is that the pipes are still wet and that water will drain into the low spots. There’s a little more water that comes out the second time.

    Whether or not it’s enough to make a difference, I don’t know. The second blow-out only takes a few minutes.

    I’ve also found that if I raise the front as high as the tongue jack will go, the water heater will drain below the level of its drain plug. I only remove the plug once a year to flush the water heater and not every time I winterize. (We take several trips each winter so I have to winterize on each return.) My water heater is behind the wheels–this might not work for your trailer.

    • I replaced my water heater plug with a valve I can quickly open. First, it’s good to be able to get sediment out regularly. Second, I have to winterize at least twice, because in MN it is freezing in October, and still freezing in April and I travel south sometime between. That water heater must get emptied before I leave and again sometime during the drive back, usually before getting to Iowa. Then water heater empty valve, along with the blow-out plug make this a 5 minute task.

  9. I “made” an adapter that attaches to my hot water heater and apply a vacuum to the line. With open valves all the water in the system is sucked out. Nothing remains behind.
    Pour pink stuff in the drains and you are done. Float some in the cleaned tanks.
    Move to the Deep South and don’t worry about freezing your water system.

  10. After blowing the lines, I still pump the pink stuff through them… Am I just wasting time & money ? Also, what about the holding tanks.. How much should I pour in them ? I also pump some through my macerator. Is blowing out enough to clear my water pump ?

    • I do both air and then pure AF. AF is so cheap you’ll feel stupid if you freeze lines just to save $1…

      I dont put extra AF in any tanks… a little (enough) gets into black and grey just by pinking the lines.

    • Unless you also hold down the foot valve on the toilet while pressuring the water system, or disconnect the line as it enters the toilet, that can freeze as well. Also, I run the water pump briefly while pressuring so as to remove any water there as well.


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