How to Winterize a Truma Combi: Step-by-Step RV Guide

Read this first: your rig is not our rig

Plumbing runs and bypass arrangements differ between manufacturers and even between model years. Follow your RV manufacturer's winterizing instructions for your specific coach, and use Truma's documentation as the authority on the Combi itself. Our video shows the process on our van as a real-world demonstration, not as a universal procedure.

The order that keeps you out of trouble

• Open the low-point drains and let the fresh-water lines empty.
• Locate the Truma Combi — know where it lives in your coach before you need to reach it in the cold.
• Set the water heater bypass so antifreeze never fills the Combi.
• Open every faucet, hot and cold, including the shower and any outside shower.
• Drain the Combi itself through its drain/safety valve.
• Only then introduce RV antifreeze if your procedure calls for it.

Where people go wrong

The two mistakes we see most often are skipping the bypass — which wastes several gallons of antifreeze filling a tank that should be empty — and forgetting a fixture. An outside shower, a toilet sprayer or a rarely used sink holds enough water to split a fitting.

Give the system time. Water drains slowly at first and then stops looking like it is draining at all while the lines are still shedding. Rushing the drain-down is how water gets left behind.

Dewinterizing in spring

Reverse the process deliberately: close the drains, return the bypass to its normal position, refill, then flush until the antifreeze taste and colour are gone from every fixture. Sanitize the fresh-water system before the first trip.

Check the Combi's operation on both gas and electric before you depend on it, and confirm the drain valve has fully closed and is not weeping.

Best practices worth adopting

• Write your own one-page checklist the first time you do it, and keep it in the van.
• Photograph the bypass valve positions in both states so you never have to guess.
• Winterize before the first hard freeze, not after the forecast changes.
• Keep Truma's manual for your exact Combi model with your RV paperwork.