Blowing Out RV Water Lines with an Air Compressor (The Complete Guide)

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If you are an RV owner, there are several things that you really need to know. One of these is how to properly blow out your water lines. This is an important step to winterizing your RV.

Of course, you can pay a professional- but it’s actually something that’s quite simple to do. There’s no reason to pay someone to do something that you can easily do on your own.

Ideally, you should use an air compressor to blow out your water lines. Start by draining tanks and unplugging connections. Then, locate blow out plug and connect air compressor. Blow out the lines. Disconnect the air compressor and blow out plug. Bypass the water heater and add antifreeze. Finally, turn on the water pump and circulate water and antifreeze through the system.

As you can see, this is a fairly simple process. However, we will go over these steps in detail below.

Steps to Blowing Out RV Water Lines with Your Air Compressor

Following, you will find the steps to blowing out your RV water lines using your air compressor. As we mentioned, you can pay a professional to do this for you if you don’t want to take the time to do it- but once you see how easy it is, you’re not going to want to spend the money!

Always be Safe

The very first step to any type of RV maintenance is safety. Therefore, you’ll want to make sure to disconnect gas and electricity from the water heater at least 24 hours before you plan to blow out the water lines. This gives the water time to cool down.

If you blow out the lines while they contain hot water, it can cause damage to the external components of your RV. If you’re in a hurry, you can speed up this process by turning off your water heater and then turning on all the faucets in the RV.

Once the water starts to come out cool, you can start draining the lines. However, you’ll want to take precautions to avoid overflowing the gray tank during this step.

Drain Tanks/Unplug Connections

Before you connect your air compressor, there is some prep work that must be done. You need to make sure the holding tanks in your RV are drained- including black water, greywater, and freshwater.

For draining your black water and greywater, you’ll need to connect the sewer hose and drain as if you’re dumping at a standard dumping station. Most freshwater tanks have a manual clear out on the bottom that allows you to manually drain the tank.

This drain can be used to save time instead of running the pump to pull the water from the freshwater tank into the greywater and black water holding tanks.

If you have a water filtration system in your RV, it should be disconnected before you move to the next step. In addition, make sure that all water left inside the water heater or water lines is completely drained out.

Finally, turn on all hot and cold faucets in the sinks to ensure that all excess water drains through and out of the holding tanks.

Locate the Blowout Plug

Once all the water has been drained, it’s time to find the blowout plug. This is an accessory that connects to your water inlet and is typically found on the side of the RV or in the storage compartment underneath.

Many times, this is labeled as “City Water Connection”. Typically, the blowout plug is made of sturdy plastic, but in some cases, it may be made of stainless steel with a corrosion resistant finish.  

If you try to blow out the lines without the blowout plug, you can cause damage to your water lines. Therefore, it’s an essential component to find and connect to the water intake outlet before hooking up the other end to your air compressor.

Connect Blowout Plug and Air Compressor

The next thing you need to do is connect the blowout plug to the exterior water inlet of your RV. Once that is done, you can connect the air hose from your air compressor to the blowout plug.

Make sure to set the PSI on the air compressor between 30 to 40 PSI. This will ensure that you don’t damage the water lines by using too much pressure.

Blow Out RV Water Lines

At this point, you’re ready to turn on the compressor and blow out the water lines. Be sure to open the water lines up one at a time to ensure each is blown out completely. Once you blow out one line, close it and move to the next.

Ideally, to maximize your efficiency in this part of the process, you need to locate all of the valves for your water lines. Additionally, this will keep you from accidentally damaging your lines by closing a valve that you intended to keep open.

Keep in mind that most RVs will have at least two water lines: one for hot and one for cold- but in some cases, there are separate lines that run through the hot water heater. Make sure that you locate and open all valves to ensure all the water is drained from your RV.

Disconnect Compressor and Blowout Plug

Once you see that there is no more water exiting the holding tanks of your RV, you can shut off your air compressor and disconnect it from the blowout plug. If you are winterizing your RV, you may need to access the exterior water inlet, so you can also remove the blowout plug at this time. However, since the plug is so small and easy to misplace, make sure that you store it in a safe and secure location.

Bypass the Water Heater

Most RV water heaters will hold approximately 6 gallons at a time. If you’ve thoroughly blown out the water lines, there’s no reason to pass antifreeze through the water heater and it’s lines.

Therefore, install a bypass line to decrease the amount of antifreeze that you’ll need to use for the next steps.

Add Antifreeze to RV Water Lines

In case you don’t already know, antifreeze is a solution with a lower freezing point than plain water. This is why many RV owners choose to use it to prevent cracked/broken water pipes. Even if you can’t get all of the water out of your lines, the antifreeze with combine with the leftover water to reduce the freezing point and protect water lines.

On the other hand, it’s also possible that the leftover water could dilute the antifreeze, making it less effective. Therefore, you should make sure that you blow out as much water as possible from your lines before closing the outlets and adding 1 to 3 gallons of antifreeze.

If you’ve never added antifreeze to the water system of your RV, there are several ways that you can do it.

Most RV owners don’t pour the antifreeze directly into the freshwater holding tank because this will require hat you use more of this solution to run through all water lines. Instead, they typically will use a hand pump to add antifreeze directly into the water lines from the exterior water inlet.

On the other hand, some RV owners opt to purchase a water pump converter kit, which can be expensive. This basically installs a bypass hose on the inlet side of your water pump to pull the antifreeze straight from the bottle.

Turn on Water Pump

No matter which method you choose to add antifreeze to the water lines of your RV, the next step is to turn on the water pump for several seconds to pull it through the water lines.

To find out if this process has been completed, open all the faucets in your RV until antifreeze flows out. Additionally, open and flush the toilet in your RV until antifreeze flows out of the bowl.

At this point, you can turn off the pump and pour another quart of antifreeze into the sink drains and toilet to ensure the traps are adequately filled and prevent them from freezing.


As you can see, blowing out the water lines in your RV is an important part of the winterization process. This will help to ensure that you don’t come back to cracked or broken water lines when camping season rolls around again. In addition to blowing out the water lines, it’s a good idea to add antifreeze to your system. Many RV owners choose to hire a professional to do this- but that’s really not necessary. This is something that you can easily do on your own and save that money for other things.

Though it does take some time, if you follow the steps outlined here, you’ll easily blow out the water lines of your RV. The good news is, the initial steps can be completed while you’re doing other things to secure your home/property for the winter. You’ll be so glad you took the time to do this!

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