PNW-Proofing Your Class A RV: A Winterization Guide for Wet, Cold Seasons

Written By BRANDON PETTERSEN

After decades of military service, we learned early on that preparation isn’t optional—it’s survival. Whether it was field gear inspections before deployment or securing equipment before a long mission, the lesson was always the same: take care of your gear, and it will take care of you. That mindset didn’t retire when we did—it followed us straight into RV life. Winterizing our Class A RV isn’t just a seasonal chore; it’s part of our operational checklist. Out here in the Pacific Northwest, cold snaps don’t always announce themselves, and one overlooked valve or water line can turn into a mission-ending repair. We’ve seen what happens when systems fail in harsh conditions, and trust us—frozen pipes are no different than failed comms in the field. Both are preventable with the right preparation. Winterizing a Class A RV is really about one thing: removing or protecting every bit of water that could freeze—because frozen water expands, and expansion cracks fittings, splits plastic valves, ruins pumps, and can quietly turn into a very expensive springtime discovery. Even though we’re technically in a “mild” winter area here in the PNW, one overnight cold snap in a water line, low-point, or outside shower can do serious damage. Considering this is our future permanent home, we take thie preventative maintenance very seriously!

Here’s a good step-by-step guide we have put together to ensure your rig stays ready for action!

 

1) Storage Winterize vs. Winter Camping Setup

A) Full winterization (storage / no water use)

You’ll drain and protect the system with RV antifreeze (pink, non-toxic propylene glycol). This is the most reliable method if the rig will sit.

B) Cold-weather use (you’ll keep using water)

You’ll focus on freeze protection: heated hoses, tank heaters, insulated bays, skirting, and keeping interior heat running. You may still winterize if you expect hard freezes and won’t be in the RV.

If you’re unsure, do full winterization. It’s faster to de-winterize than it is to repair split plumbing!

 

2) Tools & Supplies

Supplies

  • RV/Marine antifreeze (pink, non-toxic) — usually 2–5 gallons for most Class A rigs depending on method and plumbing complexity

  • Water heater bypass kit (many Class A rigs already have one)

  • Basic hand tools + screwdriver set

  • Teflon tape (for reassembly if needed)

  • Funnel, rags, gloves

  • Optional but highly recommended: blowout plug + air compressor with regulated pressure (30–40 PSI max)

Optional upgrades

  • Water pump winterizing siphon kit (if not built-in)

  • Inline water filter bypass (saves money and avoids ruining filters)

  • Heat tape / foam pipe insulation for winter camping (not storage)

 

3) Step One: Drain the Water (All of It)

Turn off heat sources

  • Turn off propane to the water heater

  • Turn off electric element (if equipped)

  • Let water cool before draining the water heater (avoid scalding)

Disconnect external water

  • Unhook city water hose

  • If you use a water pressure regulator or inline filter, remove and store them

Drain fresh/gray/black tanks

  • Dump black tank first, then gray to flush the hose

  • Drain the fresh water tank completely (via tank drain)

Open low-point drains

·      Most Class A rigs have low-point drains for hot and cold lines. Open them and let everything drip out.

·      Open all faucets (hot and cold) to help it drain faster.

Don’t forget these sometimes overlooked water spots

  • Outside shower (hot/cold)

  • Washer/dryer hookups (if equipped)

  • Toilet sprayer / bidet line (if installed)

  • Refrigerator water/ice maker line (if you have one—often overlooked)

  • Water filtration systems (whole-coach or under-sink)

  • Any additional wet bay sprayer/hose connection

 

4) Drain and Bypass the Water Heater (Critical)

The water heater is a big reservoir of water—if you fill it with antifreeze without bypassing, you’ll waste gallons.

Drain the water heater tank

  • Remove drain plug/anode rod (Suburban often uses an anode rod)

  • Open pressure relief valve briefly to let it drain faster

  • Let it empty completely

Bypass the water heater

Use the bypass valves (common 2- or 3-valve setup) so antifreeze does NOT enter the heater tank.

Rule: Water heater bypass ON before you pump antifreeze.

 

5) Choose Your Winterizing Method

Option 1: Antifreeze via the water pump (most common, most reliable)

This pushes antifreeze through the entire plumbing system.

Steps

  1. Close low-point drains after draining is finished.

  2. Set water heater to bypass.

  3. If you have an inline water filter, bypass it (or remove cartridges).

  4. Put the pump winterizing siphon tube into the antifreeze jug (or connect to the winterizing port).

  5. Turn on the water pump.

  6. Starting at the faucet farthest from the pump, open cold until it runs pink, then hot until it runs pink.

  7. Repeat for every faucet and fixture:

    • Kitchen sink

    • Bathroom sink

    • Shower

    • Outside shower

    • Toilet (flush until pink appears in bowl)

    • Washer hookups (briefly run hot/cold if you have valves for them)

  8. Pour a cup or two of antifreeze into each drain:

    • Kitchen sink drain (protects P-trap)

    • Bathroom sink drain

    • Shower drain

  9. Add antifreeze to:

    • Toilet bowl (keeps seal lubricated and prevents freeze cracking)

Option 2: Blow out lines with compressed air (cleaner, less antifreeze)

This method uses air to purge the plumbing, then you still add antifreeze to traps and toilet.

Steps

  1. Water heater drained and bypassed.

  2. Fresh tank drained; low points open, then close.

  3. Connect blowout plug to city water inlet.

  4. Regulate compressor to 30–40 PSI max (higher can damage fittings).

  5. Open each faucet one at a time (cold then hot) until only air comes out.

  6. Don’t forget toilet and outside shower.

  7. Still pour antifreeze into all drains/P-traps and toilet bowl.

6) The Wet Bay, Valves, and Exterior Plumbing

Class A rigs (including ours) often have plumbing concentrated in the wet bay, and it’s usually the coldest spot.

Checklist:

  • Winterize the wet bay sprayer hose

  • Cycle/flush any black tank flush line if possible (some people briefly run antifreeze through it, but follow your manufacturer’s guidance)

  • Make sure any diverter valves are set so antifreeze reaches all branches

  • Insulate or cover the city water inlet area if you’re winter camping

7) Protect Appliances and Add-Ons

Ice maker / fridge water line

If your fridge has an ice maker, that line can freeze. If you’re storing:

  • Shut off the supply

  • Consider draining/clearing the line (varies by RV design)

Washer/dryer

If equipped, winterize those supply lines and traps. Some setups need special attention—check the appliance manual.

Water filters

Remove filter cartridges for storage (they can crack and they trap water). Bypass if possible.

 

8) Batteries, Power, and Electronics

Batteries

  • Fully charge before storage

  • For flooded lead-acid: check water levels (use distilled water)

  • If possible, store in a maintained state:

    • Leave on a quality converter/charger designed for storage, or

    • Use a smart maintainer, or

    • Disconnect the negative cable (stops parasitic draw) and recharge periodically 

Inverters/parasite loads

Class A rigs often have many phantom draws (dash electronics, leveling system memory, Wi-Fi boosters). Consider:

  • Battery disconnect switch ON/OFF behavior varies—confirm what it actually disconnects!

  • Pull fuses for known loads if needed

 

9) Tires, Chassis, and Exterior Storage Prep

Tires

  • Inflate to proper storage pressure (per your weight/load chart)

  • Park on boards or pads if possible (helps with moisture and cold ground)

  • Move slightly every few weeks if you can, or use tire cradles

  • Cover tires to protect from UV (even in winter)

 Seals and roof

  • Clean and inspect roof seals and window seals

  • Address cracks now, not after freeze/thaw cycles worsen them

Slide-outs

  • Clean slide seals

  • Apply manufacturer-approved seal conditioner (don’t use petroleum products)

Rodent prevention

  • Seal access points (screens, foam, mesh)

  • Remove food and scented items

  • Use deterrents (peppermint packs, traps, etc.) as your comfort level allows

  • Check engine bay wiring areas—Class A rigs can attract critters

 

10) Interior Prep: Moisture Control and Mold Prevention

Especially in the Pacific Northwest, our biggest enemy is humidity.

  • Clean and dry everything thoroughly

  • Leave interior doors and cabinets slightly open for airflow

  • Use moisture absorbers (DampRid or similar) or a small dehumidifier if you have power

  • Remove linens or store them in sealed bins

  • Crack roof vents slightly if your vent covers allow it (and it’s safe from wind-driven rain)

 

11) Final “Did We Miss Anything?” Checklist

Run through this before you walk away:

Plumbing

  • Fresh tank drained

  • Water heater drained and bypassed

  • Low-point drains opened to drain, then closed

  • All faucets ran pink (or fully blown out)

  • Toilet flushed pink + antifreeze left in bowl

  • P-traps protected (antifreeze in drains)

  • Outside shower winterized

  • Filters removed/bypassed

Storage

  • Batteries charged/maintained/disconnected

  • Propane off (if storing)

  • Tires inflated + covered

  • Moisture control set

  • Food removed + rodent mitigation done

BRANDON PETTERSEN
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