An Informative Guide on How to Blow Out RV Water Lines

Blowing out your RV waterlines will prevent them from freezing and cracking over the cold winter. A split water line can cost thousands of dollars in repair work to your RV and stop you from enjoying a season of camping with friends and family.

Here’s a rundown of how to blow out RV water lines:

  • Switch off all electric-powered devices and unplug filtration systems.
  • Open the water valves and drain excess water.
  • Empty the black water tank and gray water tank.
  • Connect the blowout plug to the RV and join the other end to an air compressor.
  • Open the water lines and holding tank outlets and blow air through them via the compressor.
  • Turn off the air compressor and remove the blowout plug.
  • Coat with antifreeze.

In this guide, we’ll elaborate on how to blow out RV water lines, why it’s important, and how to maintain your efforts. 

how to blow out rv water lines

What Water Lines Are Used in RVs?

There are essentially three types of water lines available for use in RVs:

  • Copper water lines
  • Polybutylene
  • PEX or plastic water lines

Copper water lines are mostly found in older RV models. They are primarily used because the supply lines are easy to manufacture. Also, they are environmentally friendly — they don’t leave a large carbon footprint and can be recycled.

However, copper plumbing is rigid and difficult to use in compact spaces. Also, it does not do well with water acidity, which means if you’re supplying water from a well nearby, the copper lines could split.

As the risks of copper plumbing outweighed the benefits, RV manufacturers started using a new water line called PEX. It’s a combination of plastic tubing connected with a metal fitting, and it’s flexible enough to fit into any shape.

Also, the PEX RV plumbing system is exceptionally durable and lasts for up to 50 years. It is lightweight too and no level of acidity in the water will ruin the material.

PEX tubing is available in every hardware store, and it is generally recommended to keep some on hand for emergency situations.

Why Do You Need to Blow Out Water Lines in an RV?

Commonly done as a method of winterizing an RV, blowing out water lines is an essential part of upkeeping your vehicle so that it is ready for travel all year round. Here are a few benefits of blowing out water lines in an RV:

  • Prevents Frozen Water Lines

Blowing out water lines is a key aspect of winterizing an RV. It prevents the water lines from freezing when temperatures fall below 30°F. This protects the plumbing system from splitting and causing a leak. Exposure to water can also cause metal tubing to rust and leave a musty smell in the RV.

  • Cuts Down on Repair Costs

Properly blowing out the water lines prevents damage to the plumbing system. This will save a lot of money in your budget for traveling and other expenditures related to the RV. In fact, it is cheaper to spend money on winterizing the RV (even professionally) than it is to get the plumbing system repaired at a maintenance facility.

  • Long-lasting

Depending on how well the blowout process is done, it can keep the water lines from freezing for more than two winters. The easy procedure can also be followed to replace a water heater and other components of the RV and extend the life of the system. 

How to Blow Out RV Water Lines

The easiest and the most effective method used to blow out RV water lines is an air compressor. Here’s the complete guide on how to blow out RV water lines using an air compressor.

  1. Turn Off Power

First, switch off all electric-powered motors and gas lines – at least 24 hours before you’ve scheduled to blow out the water lines. Also, unplug filtration systems.

  1. Let Gravity Remove Water

Open up the sink, shower, and toilet drains so excess water is drawn out with the help of gravity.

  1. Drain Residual Water

Connect a sewer hose to a tank outlet and empty out the RV black tank, gray tank, and even the freshwater tank. There shouldn’t be a drop of water left.

  1. Attach a Blowout Plug

Connect a blowout plug to the specific inlet available in the RV. It’ll either be on the side where the black tank outlet is or in the underbelly of the RV.

  1. Bring in the Air Compressor

Join the other end of the blowout plug to the air compressor hose and adjust the pressure between 30 psi and 40 psi. 

  1. Switch on the Valves

Turn on the air compressor and, one by one, open up all the water lines including the holding tank outlets and blow air through them. Make sure to purge all valves including lines running from the water heater so nothing is left that could freeze.

  1. Unplug the Air Compressor

When the water lines have been completely blown out, i.e no water is left in any of the valves, turn off the air compressor and remove the blowout plug.

  1. Coat with Antifreeze

Double check if the water lines have been completely dried off, then pour at most three gallons of antifreeze solution to eliminate any risk of plumbing damage.

Advantages of Using an Air Compressor to Blow Out RV Water Lines

I always recommend using an air compressor for blowing out RV water lines. This is because it makes the process of blowing out your RV water lines simple and easy.

Here are a few other benefits of using an air compressor to blow out RV water lines:

  • Efficient Method

Using an air compressor to blow out water lines is easier because you only need the mechanical device and some general knowledge of all the water valves present in the RV.

  • Eliminates the Use of Antifreeze

When winterizing with an air compressor, antifreeze is just used as a fail-safe tool to keep the toilet and washing machine tubes from freezing in the winter. Other than that, it isn’t really required. This also helps you save more money because you don’t use as much antifreeze. 

  • Does Not Leave an Aftertaste

To ensure the antifreeze method works, you’ll need at least 10 to 15 gallons of solution, which will inevitably leave a strong aftertaste along with a musty smell in the air of the RV. In contrast, with an air compressor, there is no lingering taste as all it does is blow air through the pipes.

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How to Maintain RV Water Lines

Since water lines are a primary tool of water supply, it is important to optimize them. Some ways you could do this include:

  • Regulate the Water Pressure

Water lines are flexible and durable but thin, meaning high water pressure can easily split the line and cause a leak. Invest in an RV water pressure regulator to prevent this from happening.

  • Sanitize the Water Lines

Most RVers recommend using bleach to sanitize the RV water lines and keep them fresh and free of all obstructions.

  • Install a Water Line Filter

As the name suggests, an RV water line filter strains out particles that can cause clogs and removes pungent odors to keep the environment pleasant.

Frequently Asked Questions

What happens if you don’t winterize an RV?

If an RV isn’t properly winterized, water will freeze in the lines which will cause them to split and leak water. You could use antifreeze if the RV is going to stay in storage when temperatures fall below 30°F. The preferred solution is to use an air compressor to remove water so there’s no lingering taste of antifreeze.

Is an air compressor the best option for blowing out RV water lines?

Yes, using an air compressor is the easiest and safest method to blow out water lines. The procedure is easy to follow, cost-effective and multi-purpose i.e can be used while winterizing the RV or replacing the water heater. Plus, it doesn’t leave an odor like antifreeze does in a winterized RV.

Does antifreeze hurt RV water lines?

No, antifreeze does not hurt an RV’s water lines as long as it is specifically targeted at an RV’s plumbing system. It’ll keep residual water from freezing in the water pipes and splitting the line. However, regular automotive antifreeze can harm the septic system of an RV.

What is the easiest way to blow out RV water lines using an air compressor?

Generally, most RV campers employ a hybrid method in which they first open the faucets, pipes, and low-point drains so water runs out via gravity and then use a 2 to 3-gallon air compressor to remove any residual water. This cuts down on the manual work and removes the risk of water buildup in the pipelines.

What happens if RV water lines freeze?

When water lines in an RV freeze, they split and leak water inside the RV. It can be a mess to clean up, especially if there is a limited supply of cleaning rags, toilet paper, or even newspapers that would easily soak up the water.

In Closing

With all this knowledge on how to blow out RV water lines, you can now enjoy a steady stream of hot water in winter and clean water in the pipelines all year round!


Beau is an electrical engineer with a knack for DIY repair and construction. When he's not tinkering with his projects he's on the road travelling and enjoying an exciting lifestyle with his young family.

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