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How to Blow Out RV Water Lines

Blowing out the water lines is one of the most important steps of winterizing your RV. So if you plan to dock your RV for the winter or have it sit in a potentially cold area for a while, blowing out the water lines is a good start.

But how do you blow out the water lines on your RV? What tools, equipment and expertise do you need to properly winterize your RV?

The best way to blow out your RV water lines is to use a compressor and blowout plugs. The compressor forces air into your RV water lines and removes water. 

How do I get started blowing out the water lines in my RV?

There are a few safety precautions to take before you start blowing out the water lines for your RV. A little planning is helpful here.

  • Start by turning off your water heater about one day in advance. This will prevent hot water from entering the lines.
  • Make sure the drain tanks are open
  • Drain your gray and blackwater tanks. You won’t necessarily need to drain your freshwater tank using this method. Disconnect your water supply and turn the drain pump off so water doesn’t continue to move.
  • After your water heater is cooled, drain the water heater by opening the pressure valve (or your water heater manuals specified method)
  • Turn on all faucets to allow both excess hot and cold water to drain

This will ensure that all the water within your RV is out and leaves only excess water that could be sitting somewhere in lines.

Using an air compressor to blow out the RV water lines

A couple more steps here before we really blow the air line of your water lines.

  • Locate the RV water inlet on the exterior of your RV. This will be close to your tanks is generally in a panel on one side of your vehicle. It probably won’t be on back.
  • Install a blowout plug in the RV water inlet. This usually screws in by rotating it right.
  • Set the air compressor to 30 to 40 pounds per square inch, you shouldn’t need more than this pressure.
  • Screw the air compressor hose into the blowout plug, generally be turning right on the nut on the neck of the hose.
  • Turn the compressor on and let it blow in for about 2 minutes.
  • Turn the compressor off.

Blowing out the airlines

  • Open the water valves to drain them one by one – assuming you have multiple water valves for the purpose – you’ll generally have at least one hot and one cold. 
  • You can also add more air pressure to individual lines by inserting the air compressor hose into the valve

You’ll now want to let your tanks drain again to release any excess water that was removed by the air pressure. You won’t really know if there is more air trapped in the lines, so the best sign that your air pressure worked is that a little water comes out.

You can now remove the blowout plug from the water inlet and replace it with a regular water intake.

Safety precautions

Here are a few safety tips

  • Don’t get your air compressor to higher than 30 to 40 PSI. Using higher pressure can damage the lines. 30 to 40 is enough to push water around.
  • You might want a 10 gallon compressor to start, at least. While 2 gallon compressors are available, that might not be enough air to completely pressureize a larger RV’s water lines. Rather than doing the process repeatedly or slowly, a larger compressor is more efficient and will draw more water out, making your winterization more effective.
  • Store the blowout plug in a safe place. It’s not dangerous, it’s just a rather small tool that you might need in a pinch when winterizing and it’s good to keep it someplace you’ll remember.
  • Put the air compressor away right away. Kids can accidentally use it and cause potential problems – air comes out really fast.

Why am I blowing out my water lines?

Water can get trapped in various places in your RV’s water lines. When the temperature starts to drop, that water can readily freeze into ice. Ice expands and fills the water line tubes and can cause blockages – or worse yet, breaks and flooding. 

Blowing out RV water lines is especially important if you plan to have your RV sit for a while, unused. If you plan to use your RV in the cold, it’s also a good idea to add RV specific antifreeze to the water in the amount suggested on the bottle. 

RV antifreeze has a lower freezing temperature than water and will keep water from freezing. This is also a good idea generally if you plan to keep water stored in the RV just in case you do go somewhere.

Overall, whether you are planning to go somewhere or not, blowing out your water lines while not immediately using your RV is a good precaution to take in that event the weather suddenly gets colder.

This process is much like wrapping your home’s exterior water spigot with insulation or cutting off the water supply to the spigot. It’s a bit more important in an RV because there is a better chance of water freezing.

Conclusion

Blowing out your air lines is one essential step in winterizing your RV. This is especially true if you plan to have the RV sit for a while. It’s also a great precaution in case a cold snap catches you.

A few simple rules are to use a large enough compressor – like 10 gallons or more, for your RV, and keep that blowout plug safe. You might need it suddenly!

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