RV AFTERMARKET
Winterization Done Right: Prevent Post-Storage Problems Before They Start
Proper winterization practices to protect toilets and water heaters during storage.
By Scott Lickteig
Images courtesy of Dometic
Winterization must start before the first freeze.
You see it every year. RVs come out of storage with leaking toilets, cracked water heaters and broken valves. The most common cause: improper winterization.
Even after lines are drained, water can remain in the system. When that water freezes, it expands by up to 9%, rupturing pipes, cracking fixtures and destroying water pumps.
A few extra minutes spent on proper winterization can prevent springtime service calls before they start. Make sure every rig that leaves your bay is properly winterized before the first freeze, so your customers are road-ready when camping season returns.
Start with the method, then focus on the two systems most vulnerable to freeze damage: toilets and water heaters. Here is a practical guide to do just that.
Winterization Methods
Not all RVs are winterized the same way. Start with the method.
The two most common approaches are the antifreeze method and the compressed air method. Know the options, then choose the one that best fits your customer’s setup.
Method 1: Antifreeze Method
- Set the water pump to winterization mode.
- Insert siphon. Place the siphon hose directly into RV antifreeze.
- Turn on the water pump to introduce antifreeze. • Do not use ethylene glycol-based antifreeze. • Do not dilute the antifreeze with water.
- Start with the faucet closest to the pump. Open the hot and cold valves individually. This ensures antifreeze reaches water lines and displaces trapped water.
- Confirm antifreeze reaches all fixtures, valves and components.
- Protect traps. Pour 1-2 cups of antifreeze down every sink and shower drain. Leave a small amount in the toilet bowl to protect the seals from freeze damage.
Pros: Ensures complete protection and easy to verify.
Cons: Requires 2-3 gallons of antifreeze and may leave a slight taste that requires flushing.
Method 2: The Compressed Air (“Blow-Out”) Method
- Attach adapter. Screw a blow-out plug into the city water inlet.
- Set pressure. Adjust the air compressor to 30-50 psi.
- Connect air.
- Remove remaining water using compressed air. Open the faucet closest to the inlet.
- Clear the pump. Turn on the water pump for 30 seconds to clear line.
- Protect traps. Pour 1-2 cups of antifreeze down every sink and shower drain. Leave a small amount in the toilet bowl to protect the seal.
Pros: No antifreeze taste and fewer chemicals used.
Cons: Requires an air compressor. Harder to verify complete water removal. Still requires antifreeze for traps.
The 5 Winterization Mistakes We See Most Often
- Forgetting to bypass the water heater
- Leaving water trapped in toilet valves
- Using automotive antifreeze instead of RV antifreeze
- Forgetting sink and shower traps
- Returning the RV to service with the bypass still engaged
Plumbing should be your top priority. Freezing water can cause some of the most costly and extensive damage during winter storage. Take the time to properly winterize.
Toilets & Water Valves
Winterizing comes down to fully draining the plumbing. Improper winterization can leave toilets and water valves damaged when they return for the season.
Start here:
- Thoroughly flush the system with fresh water.
- Empty the holding tank.
- Shut off the water supply to the toilet and remove the inlet water line.
- Push the flush lever until all the water is drained from the toilet and the water valve.
- Drain the potable water tank.
Always drain the waste tank first, followed by the gray tank. The gray water helps to rinse.
How To Winterize With Antifreeze
- Add antifreeze to the potable water tank.
- Reconnect the water inlet to the toilet. Flush the antifreeze through the system into the holding tank.
- Verify antifreeze reaches the water valve and vacuum breaker. This is a visual inspection.
- Turn on the pump. Run until you see the pink antifreeze.
How To Winterize With Compressed Air
- Confirm water has been removed from vulnerable toilet components.
- Take additional precautions by further draining or disconnecting water valves after blowing out lines to remove all trapped water.
Freeze damage is one of the most common post-winter service issues, not product defects. Following these steps can help reduce repairs, prevent callbacks and keep service bays moving for the busy season.
Water Heaters
Water heaters are next. If a tank is not fully drained before storage, retained water will freeze, expand and crack the tank. Take these extra steps:
- Turn off the main water supply.
- Allow the water heater to cool completely (30 minutes).
- Remove the drain plug or anode rod to drain the water heater. If the water is not a steady stream, open the pressure/temperature relief valve to allow air into the tank. If needed, use a small gauge wire to poke through the drain coupling, dislodging obstructions.
- Flush out the sediment. With the tank drained, around 2 quarts of water should remain. This water contains harmful corrosive particles. Simply running water through the inlet does not stir up and flush out all sediment. To remove, use a commercially available RV Water Heater Flushing Tool, suspending and flushing the materials back out of the drain coupling. Continue flushing until the water runs clear.
- Replace the drain plug. Remember: An undrained tank with a water level above the drain plug level will crack.
- Close the cold-water inlet and hot-water outlet valves and open the bypass valve.
Winterizing With Antifreeze
Route RV antifreezes through the plumbing system while bypassing the water heater tank.
Winterizing With Compressed Air
Turn the valves to the bypass position, ensuring there’s no wasted compressed air.
“Common mistakes often are not discovered until the RV has returned to service,” says Jason Stutsman, Dometic technical service trainer. “One of the most common is forgetting to close the bypass before returning to normal operation. Cold water then mixes into the hot water line, causing only lukewarm water to be delivered.”
Understanding the difference between winterization mode and operation mode is important so you can prevent avoidable service calls and customer complaints season after season. For a deeper dive, the Dometic Product Academy is a go-to resource for winterization training videos, service resources and best practices.
Scott Lickteig is the customer experience technical service and warranty manager at Dometic, where he oversees technical service and warranty support to help dealers and customers navigate complex challenges. His experience is focused on strengthening service operations and ensuring Dometic remains a trusted, reliable partner throughout the ownership journey.
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