Complete Guide On How To Blow Water Out Of RV Lines
Winterizing your recreational vehicle by blowing out the water lines with compressed air prevents catastrophic freezing damage to pipes, fittings, and appliances. By regulating air pressure to a maximum of 30 to 40 PSI and systematically purging every hot and cold water fixture, you eliminate lingering moisture that expands and cracks plumbing infrastructure during sub-freezing temperatures.
Essential Preparation and Equipment Setup
Proper winterization requires meticulous preparation and the right mechanical adapters to safeguard your RV fresh water system. Attempting to blow out lines without an adjustable pressure regulator risks over-pressurizing and bursting PEX piping, flexible hoses, or internal pump components.
- Essential Gear and Tools: A portable air compressor capable of delivering at least 40 PSI, a specialized brass or lead-free RV blow-out plug (male garden hose thread to Schrader tire valve), an adjustable inline water pressure regulator, Teflon tape, and standard hand tools for accessing low-point drains.
- Prerequisite Knowledge and Standards: Familiarity with your specific RV plumbing layout, including the location of the water heater bypass valve, water pump strainer, and low-point drain plugs. All operations should be performed on a level surface with the shore power disconnected and the water heater completely cooled.
- Time and Budget Benchmarks: This maintenance procedure typically takes 45 to 60 minutes to complete. Budget requirements are minimal if you already own an air compressor, or roughly 20 to 50 dollars for basic adapters and pressure regulators.
Step-by-Step RV Plumbing Winterization Workflow
Step 1: Drain and Isolate the Water Heater
Begin by turning off the water heater power source (both 120V AC electric and 12V DC propane) and allow the tank to cool completely to avoid scalding injuries. Open the exterior water heater access panel, remove the nylon drain plug or pull the pressure relief valve, and open an interior hot water faucet to vent the tank and allow the water to drain out completely.
Warning: Never apply compressed air to a water heater tank. Always close or configure your water heater bypass valves to isolate the tank before introducing compressed air into the rest of the RV plumbing system.
Step 2: Open Low-Point Drains and Fixtures
Locate the low-point drain lines underneath your RV, which typically consist of hot and cold PEX pipes protruding through the underbelly with threaded caps or shut-off valves. Remove the caps or open the valves to let gravity purge the bulk of the standing water in the system, and simultaneously open all interior hot and cold faucets, the shower, and flush the toilet to maximize gravity drainage.
Pro-Tip: Catch the draining grey and black water in a portable tote or bucket if you are winterizing at home, and leave all interior faucets open during the initial drainage phase to break internal vacuums within the pipes.
Step 3: Install the Blow-Out Plug and Regulate Air Pressure
Locate the city water inlet on the exterior of your RV, which features standard garden hose threading. Attach your adjustable water pressure regulator to the city water inlet, setting the output limit strictly between 30 and 40 PSI to protect delicate plastic fittings. Screw the RV blow-out plug into the pressure regulator, and connect your air compressor hose to the Schrader valve on the plug.
Step 4: Systematically Purge Every Water Fixture
Activate your air compressor and allow it to build pressure, ensuring the output regulator remains locked at 30 to 40 PSI. Working in a methodical sequence from the fixture closest to the city water inlet to the one furthest away, close one faucet at a time, apply air pressure, and open the valve until only a fine mist or dry air emerges. Repeat this process for:
- Bathroom sink hot and cold taps
- Shower or bathtub valves and handheld showerhead
- Toilet flush valve (hold open until air stops expelling moisture)
- Kitchen sink hot and cold taps
- Exterior shower or wash station
- Ice maker supply lines and washing machine connections if equipped
Step 5: Clear the Water Pump and Prap P-Traps
Disconnect the air compressor and remove the blow-out plug from the city water inlet. Locate your 12V DC water pump, open the inlet strainer bowl, empty any trapped water, and re-install it loosely. Turn the water pump on for just 3 to 5 seconds with all low-point drains open to expel any residual water trapped inside the pump diaphragm, then immediately turn the pump back off to prevent dry-running motor damage. Pour a cup of RV-rated non-toxic antifreeze down every sink, shower, and floor drain to fill the P-traps and protect them from freezing.
Camco RV Brass Blow Out Plug | Helps Clear Your RVs Water Lines During ...
Technical Parameters of RV Winterization Methods
| Winterization Parameter | Compressed Air Blow-Out Method | RV Antifreeze Pumping Method | Combined Air and Antifreeze Method |
|---|---|---|---|
| Maximum Operating Pressure | 30 to 40 PSI strictly enforced | N/A (Gravity or pump pressure) | 30 to 40 PSI for air phase |
| Primary Advantage | Zero chemical taste in spring; highly cost-effective | 100 percent freeze protection for forgotten pockets | Maximum defense against extreme sub-zero temperatures |
| Environmental Impact | None; completely dry lines | Requires proper disposal of pink fluid | Requires minimal fluid disposal |
| Ideal Climate Application | Moderate to mild winter zones | Severe sub-zero northern climates | Extreme cold climates and long storage periods |
Common Winterization Failures and Field Fixes
- Root Cause: Water heater bypass valves left in the wrong position during the blow-out process, allowing moisture to re-enter the tank or trap water in internal loops.
- Actionable Fix: Inspect your specific bypass valve manifold layout (typically a two-valve or three-valve system), re-configure them to isolate the tank, and repeat the compressed air purge through the hot water lines.
- Root Cause: A failing check valve inside the city water inlet allowing compressed air to escape backward instead of traveling through the internal plumbing network.
- Actionable Fix: Depress the pin inside the city water inlet temporarily with a small tool to clear debris, or unscrew and replace the spring-loaded city water entry valve if the seal has degraded.
- Root Cause: Residual water pooling in low-lying flexible hose dips or sagging PEX lines that resist gravity and air pressure displacement.
- Actionable Fix: Manually elevate or massage flexible hoses while applying compressed air pulses to force trapped pockets of water toward the nearest open drain valve or fixture.
Frequently Asked Questions
What is the ideal air pressure for blowing out RV water lines?
Maintain your compressor output pressure between 30 and 40 PSI using a dedicated inline regulator. Exceeding 40 PSI can rupture factory crimp rings, fracture older PEX tubing, or destroy sensitive internal components in appliances like your water heater or toilet valve.
Do I still need RV antifreeze if I use compressed air?
If you live in a region with mild winters where temperatures rarely drop below freezing for extended periods, a thorough compressed air blow-out is usually sufficient. However, if your RV experiences severe sub-zero temperatures, pumping propylene glycol RV antifreeze through the lines after blowing them out provides foolproof insurance against cracked pipes.
Should I leave my low-point drains open or closed after winterizing?
Leave both your low-point drain valves and all interior faucets open throughout the entire storage period. This ensures that any condensation or residual moisture that accumulates inside the lines has a clear path to escape rather than pooling and freezing.
How do I clear the RV toilet and black tank flush lines?
Hold the toilet flush pedal or button down continuously while applying compressed air to the system until only air escapes the bowl. For the black tank flush inlet, use a separate dedicated blow-out adapter to clear the exterior vacuum breaker and rinse line, as tying this into the fresh water system cross-contamination standards is prohibited.
Secure your recreational vehicle's plumbing system against winter damage today by gathering your pressure regulators and executing a complete, pressure-regulated air purge.
