How to Winterize an RV: A Class B Winterization Checklist

Winterizing an RV means protecting systems that can be damaged when temperatures drop below freezing. Water left in a line, pump, strainer, fixture, or waste component can freeze and expand, potentially turning a small amount of trapped water into an expensive repair.

For Class B owners, the compact footprint doesn’t make winterization a one-size-fits-all process. Plumbing layouts and winterization connections vary by manufacturer, model, and sometimes production date.

This checklist helps you understand what needs attention, what you can easily overlook, and when your RV’s specific instructions take over.

When Should You Winterize Your RV?

Don’t use the first snowfall as your reminder.

What matters is whether your RV will be exposed to freezing temperatures and how you’ll use or store it when those temperatures arrive. If the van will sit without its systems being actively protected from the cold, winterization should happen before a hard freeze.

That timing is especially important in Colorado. Overnight temperatures can vary significantly with elevation, and an early-season mountain trip can expose an RV to freezing conditions even while daytime temperatures remain comfortable.

Before putting winterization off for another weekend, consider:

• the overnight forecast where the RV will be parked;
• the elevation;
• whether the RV will remain in regular use;
• whether it will be heated while parked; and
• how long it will sit between trips.

Winterizing for storage is different from continuing to use your RV through the colder months. If you’re planning more trips after temperatures begin to fall, driving a Grech RV in winter conditions comes with its own considerations, including changing road conditions and cold-weather operation.

Preparing early gives you time to work through the process carefully instead of reacting to an unexpected freeze.

Before You Start: Check the Procedure for Your Class B

A general RV winterization checklist can tell you what needs protection. Your manufacturer’s instructions tell you how to protect it.

Grech’s own winterization procedures demonstrate why that distinction matters.

For the Strada and the Terreno procedure covered in Grech’s instructional video, owners first drain the freshwater tank, then add four gallons of RV antifreeze through the freshwater fill. The water pump circulates the antifreeze through the plumbing.

Grech’s earlier Turismo instructions also call for four gallons of RV antifreeze in the freshwater holding tank, although the process for draining the freshwater and waste systems differs.

However, Grech updated the process for Turismo units produced in November 2023 and later. Those units use a bypass valve and a 1/2-inch-ID pickup tube to draw RV antifreeze directly from its container. Grech states that with this setup, you no longer need to pour antifreeze into the freshwater holding tank.

That’s a meaningful difference within a single model line.

Before you start, identify your model and production date, then find the winterization instructions that apply to your RV. Don’t assume a video showing a similar-looking Class B uses the same plumbing configuration.

Class B RV Winterization Checklist

Once you know which procedure applies to your RV, you can work through the systems that need protection.

1. Dump the Waste Tanks

Start by emptying the black and gray tanks at an appropriate dump station.

How the waste system is handled during winterization depends on its configuration. For example, Grech’s Strada and Terreno procedure includes running RV antifreeze into the macerator pump, while the applicable Turismo instructions use a different waste-drain arrangement.

2. Drain the Freshwater System

Next, remove the water from the freshwater system using the procedure specified for your RV.

Don’t think only about the freshwater tank. Water can remain elsewhere in the system, which is why the location of drains, strainers, pumps, and other components matters.

One particularly useful example comes from Grech’s updated Turismo instructions. Owners are told to remove the water-pump strainer basket and empty the water inside. Grech warns that leaving standing water there can allow it to freeze, expand, and crack the basket.

It’s a small detail with a clear consequence, and a good reminder to account for places where residual water can hide.

3. Protect the Plumbing with the Correct RV Antifreeze

If your manufacturer’s procedure calls for antifreeze, make sure you’re using RV antifreeze intended for the water system, not automotive antifreeze. Grech explicitly makes that distinction in its winterization instructions.

The way antifreeze enters the plumbing depends on the RV. As the Grech procedures demonstrate, one configuration may call for antifreeze through the freshwater fill while another may draw it directly from its container.

4. Work Through the Water Fixtures

The antifreeze needs to reach the applicable fixtures and water lines.

In Grech’s Strada and Terreno instructions, owners run both the cold and hot sides of the galley faucet until a steady stream of RV antifreeze appears. The procedure then addresses the bathroom/shower faucet, toilet, and exterior shower.

That last one is easy to overlook. When you’re standing inside the van working through sinks and the shower, an exterior fixture may not come to mind right away.

Use your RV’s instructions to identify every fixture that needs attention rather than assuming the interior faucets complete the job.

5. Address Low Points and Other Places Water Can Remain

Visible fixtures aren’t the end of the plumbing system.

Depending on the RV, the procedure may also address low-point drains, strainers, pumps, waste plumbing, and other components where water can remain.

For example, Grech’s Strada/Terreno procedure calls for shutting off the water pump, relieving system pressure, and then opening the hot and cold low-point drains to release residual pressure before closing them again. The procedure also includes steps to protect the macerator.

Prepare the Rest of Your Class B for Winter Storage

Protecting the plumbing addresses the immediate freeze risk, but an RV parked for an extended period needs additional attention. Start by treating the RV systems and vehicle chassis as separate maintenance areas.

A Class B built on a Mercedes-Benz Sprinter is both an RV and a vehicle, so winter storage also means keeping up with Sprinter RV maintenance. For the Sprinter chassis, follow the storage guidance for your model year. Mercedes-Benz guidance covers fluid levels, tire pressures, battery condition, and longer periods of inactivity. One detail worth knowing: Mercedes-Benz warns against charging the Sprinter’s 12V batteries by leaving the engine idling, because prolonged idling can affect exhaust-system components.

The house electrical system also deserves its own preparation. Battery technology and system configurations differ, so follow the storage instructions applicable to the electrical system installed in your RV rather than applying generic battery advice.

Inside the coach, remove food and other items that could attract pests. Clean crumbs and spills from the galley, cabinets, drawers, and seating areas, and make sure you don’t leave damp clothing or gear inside for months.

A final walk-through is also useful. Look for moisture, leaks, damaged seals, or another issue you’d rather address now than discover when you’re ready to get back on the road.

DIY or Professional Winterization?

Winterization is manageable for owners who understand their RV’s systems and are comfortable following the applicable procedure. But there are also good reasons to have a professional handle it.

If this is your first winter with the RV, you’re unsure which winterization procedure applies, or you don’t want to risk overlooking a component, professional preparation can reduce that uncertainty.

For Grech Colorado owners, Mountain Luxe RV offers:

• Winter Storage Prep: $249 – Winterization and battery preparation. Tanks must be dumped before arrival.
• Systems Check: $450 / 1 hour – Broader systems review; repairs and troubleshooting are not included.

Any additional diagnosis or repair identified as necessary would be separate from the one-hour check.

Get Your Class B Ready Before the First Hard Freeze

Good winterization starts before temperatures become urgent.

Know where your Class B will spend the winter, check the forecast, and carefully work through the water system. If the van will sit for an extended period, prepare the chassis, electrical system, and interior for storage, too.

When warmer weather returns, the process reverses. A thorough spring prep checklist can help you bring the water system back online, inspect the coach after storage, and address maintenance before the first trip of the season.