Preparing your rig for the off-season can feel like a daunting chore, especially when you consider the damage a single frozen pipe can cause. Learning how to blow out the water lines on an rv is one of the most effective ways to protect your investment without filling your entire plumbing system with chemicals.
We understand that you want to spend more time on the trail and less time fixing burst plastic lines or cracked fittings. This guide promises to walk you through a professional-grade winterization process using compressed air, ensuring your plumbing stays bone-dry all winter long.
We will preview the essential tools you need, the specific pressure settings to avoid damage, and a step-by-step sequence that covers every hidden valve and faucet. By the time you finish reading, you will have the confidence to winterize your RV like a seasoned technician.
Why You Must Learn how to blow out the water lines on an rv Before Winter
When temperatures drop below freezing, any water trapped inside your RV plumbing expands. This expansion exerts massive pressure on PEX tubing, plastic connectors, and delicate pump internal components, often leading to hairline fractures that you won’t notice until the spring thaw.
Mastering how to blow out the water lines on an rv allows you to clear the system using air rather than just relying on RV antifreeze. While many owners use “the pink stuff,” blowing out the lines first ensures that no diluted water remains in the low spots of your plumbing.
This method is also much cleaner for your fresh water system. You won’t have to spend hours flushing out the taste and smell of antifreeze when you are ready for your first camping trip of the new season.
The Essential Gear List for Compressed Air Winterization
Before you begin, you need the right tools to ensure the job is done safely. Using a high-powered shop compressor without the proper regulations can actually blow your plumbing fittings apart, creating a bigger mess than the ice would have.
You will need a blow-out plug, which is a small brass or plastic fitting that threads into your city water inlet. This allows you to connect a standard tire chuck or air hose directly to your RV’s plumbing system.
An adjustable pressure regulator is the most critical tool in your kit. You must be able to limit the air pressure entering your lines to avoid exceeding the safety rating of your internal plumbing components.
Finally, ensure you have an oil-less air compressor. Standard shop compressors can sometimes mist small amounts of oil into the air stream, which you do not want inside your fresh water drinking lines.
Step 1: Draining the Main Tanks and Water Heater
The first step in how to blow out the water lines on an rv is to remove the bulk of the water manually. Start by opening your fresh water tank drain valve and letting it empty completely while you prepare the rest of the rig.
Next, head to your water heater. Ensure the heater is turned off and the water has cooled down completely to avoid serious burn injuries from splashing hot water.
Remove the drain plug or the anode rod located at the bottom of the exterior water heater panel. Open the pressure relief valve at the top of the tank to allow air in, which helps the water drain much faster.
Bypassing the Water Heater
Once the water heater is empty, you must turn the bypass valves. Most RVs have a series of valves behind the heater unit that redirect water flow away from the tank.
You do not want to blow compressed air into a 6-gallon or 10-gallon empty tank, as it is inefficient and can damage the tank’s internal lining. Bypassing ensures the air stays within the small-diameter PEX lines where it is needed.
If your RV does not have a bypass kit installed, you can purchase a simple three-valve bypass system at any camping supply store. This is a permanent modification that makes every future winterization much easier.
Step 2: Opening the Low Point Drains
Every RV has low point drains, which are usually two lines (one red for hot, one blue for cold) hanging beneath the chassis. These are the lowest points in your entire plumbing infrastructure.
Open these valves or remove the caps and let gravity do the heavy lifting. While these are open, go inside and open all your faucets to break the vacuum and allow the water to fall out of the lines.
Once the water stops dripping from the low point drains, close them tightly. If you leave them open while using the compressor, you won’t be able to build enough static pressure to clear the rest of the fixtures.
Step 3: Setting Up Your Air Compressor
Now it is time to connect your air source. Thread your blow-out plug into the city water inlet. This is the same connection you use at a campground to get pressurized water.
Adjust your compressor regulator to a maximum of 30 to 40 PSI. Never exceed 50 PSI, as many RV plastic fittings and flexible hoses are only rated for lower pressures, especially as they age and become brittle.
Connect the air hose to the plug. You should hear a faint hissing as the lines begin to pressurize. If your compressor is small, let it fill its tank completely before you start opening faucets.
Step 4: The Fixture-by-Fixture Blow Out Sequence
The secret to how to blow out the water lines on an rv effectively is to work from the fixture closest to the air inlet to the one furthest away. This ensures you are pushing water in one direction toward the drains.
Start with the kitchen faucet. Open the cold water side and wait until only a fine mist or pure air comes out. Close it, and then repeat the process for the hot water side.
Move through the RV in this order:
- Kitchen sink (Hot and Cold)
- Bathroom vanity sink (Hot and Cold)
- Shower head and faucet (Don’t forget to drain the hose!)
- Toilet flush valve
- Outdoor shower or spray port
Don’t Forget the Toilet and Appliances
The toilet valve is a common failure point because people forget to hold the flush pedal down long enough. Hold the pedal until you hear nothing but rushing air coming into the bowl.
If your RV has a washing machine or an ice maker, these require special attention. You may need to run a short cycle on the washer to force the internal pumps to clear the water out of the solenoids.
For ice makers, it is often best to disconnect the small plastic line at the back of the fridge. These lines are very thin and can easily freeze and crack even if the main lines are mostly clear.
Step 5: Final Clearing and P-Trap Protection
Once you have gone through every fixture twice, disconnect the air compressor. Open the low point drains one last time to see if any residual water was pushed toward them during the process.
Even if your lines are dry, your P-traps (the U-shaped pipes under your sinks) still contain water. This water acts as a seal to keep sewer gases from entering your living space.
Pour about two cups of RV-specific antifreeze (the non-toxic pink stuff) down every drain, including the shower. This will displace the water in the trap and prevent it from freezing and cracking the plastic pipe.
Finally, pour a small amount of antifreeze into the toilet bowl to keep the rubber seal lubricated and prevent it from drying out or freezing to the ball valve during the winter.
Common Mistakes When Blowing Out RV Water Lines
One of the biggest mistakes DIYers make is forgetting the water pump. Most 12V water pumps have a small strainer or filter attached to the side that holds about a half-cup of water.
If you only blow through the city water inlet, you aren’t clearing the line between the fresh water tank and the pump. Turn the pump on for about 30 seconds while the lines are open to push that remaining water out.
Another error is using too much pressure. It is tempting to crank the compressor to 90 PSI to “get it done faster,” but this can blow the seals right out of your faucets or cause a PEX fitting to pop behind a wall where you can’t see it.
Lastly, always remember to drain your black and gray tanks completely before finishing. Leaving liquid in these tanks can damage the gate valves, making it impossible to dump your waste during your first trip of the spring.
H2: Frequently Asked Questions About how to blow out the water lines on an rv
Can I use a bicycle pump to blow out my RV lines?
While technically possible, a bicycle pump does not provide the consistent volume of air (CFM) needed to push water through long stretches of plumbing. You will likely leave pockets of water in the low spots, which defeats the purpose of the task.
Do I still need antifreeze if I blow out the lines with air?
Yes, but you need much less. You still need RV antifreeze for the P-traps, the toilet seal, and the waste tanks. Blowing out the lines simply means you don’t have to put the chemicals inside your actual drinking water pipes.
How do I know when all the water is out?
You will know the lines are clear when you open a faucet and there is no sputtering or misting. The sound will change from a “gurgle” to a steady, dry hiss of air. We recommend repeating the cycle twice to be absolutely sure.
What happens if I forget to bypass the water heater?
If you don’t bypass it, you will spend a very long time trying to pressurize the 6-10 gallon tank with your compressor. Additionally, you risk blowing sediment and scale from the bottom of the heater tank into your faucets, which can clog your aerators.
Conclusion: Stay Ready for the Next Adventure
Understanding how to blow out the water lines on an rv is a fundamental skill for any owner who wants to avoid the “springtime surprise” of a flooded cabin. By using regulated compressed air, you ensure a dry, safe plumbing system that is ready to go the moment the weather turns warm.
Always prioritize safety and precision over speed. Take the extra ten minutes to check your outdoor shower and your toilet valves, as these are the most frequently overlooked components that lead to costly repairs.
Now that your rig is winterized and protected, you can rest easy knowing your plumbing is safe from the elements. Keep your tools handy, stay proactive with your maintenance, and we will see you back on the road next season!
Stay safe and stay comfortable!
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