The complete job, in order — drain, bypass, antifreeze, and check — with the numbers that matter.
Research — a researched guide built from manufacturer guidance and published owner experience. This page does not present the procedure as personally tested.
Winterizing a motorhome is mostly one job: get the water out of everywhere it can freeze, protect what you can't drain, and put the rig to bed so it survives months of cold. This checklist walks through that job in the order most owners follow it. Quantities and pressures below are typical ranges from manufacturer guidance and owner documentation — your rig's owner's manual wins over any number on this page, because models differ.
| Step | The key number | Why it matters |
|---|---|---|
| Turn off + cool the water heater | Cool to the touch before draining | Burns, and a hot drain can damage the tank |
| Drain fresh tank + low-point drains | Every faucet open, hot and cold | Water left anywhere freezes and splits fittings |
| Blow out the lines (optional) | 30 PSI max, regulated | Unregulated shop air can blow fittings apart |
| Bypass the water heater | Before any antifreeze is pumped | Otherwise you fill a 6–10 gallon tank with antifreeze |
| Pump antifreeze | 2–3 gallons typical for a Class C with bypass; until every outlet runs pink | Pink at every outlet is the proof the job is done |
| P-traps | About a cup per drain | Trap water freezes and cracks the trap |
| Batteries | Store fully charged; check every 4–6 weeks | A discharged battery is the one that freezes |
| Tires | Sidewall pressure before storage | Pressure drops ~1 PSI per 10°F; soft tires flat-spot |
| Fuel | Full tank + stabilizer dosed per label | Full tank = less condensation; treated fuel protects the system |
| Check-ins | Monthly, ~10 minutes | Catches small problems before they become spring repairs |
| Method | What it is | Verdict |
|---|---|---|
| Antifreeze only | Drain, bypass, pump antifreeze through every line | Works fine for most owners, and is the simplest reliable method. Uses the most antifreeze. |
| Blowout + antifreeze | Blow the lines out with regulated air first, then pump antifreeze | The thorough option. Air removes most water first, so the antifreeze that follows stays at full strength. This is the method this checklist follows. |
| Air only | Blow the lines out and stop there | Risky. Water can still sit in low spots, valves, and the water pump itself. Most manufacturers and experienced owners do not recommend relying on air alone in real winter cold. |
Switch the water heater off — electric and gas — and let the water inside cool completely before you touch the drain. Draining a hot tank risks burns and can damage the tank. This is step one because everything else waits on it.
Open the low-point drains (usually a pair of valves under the rig, one hot and one cold) and drain the fresh-water tank. Then open every faucet, hot and cold, flush the toilet, and run the outside shower until nothing is left. Don't forget fixtures you rarely use — the outside shower and the toilet valve are the ones that get missed, and they are the ones that split. If your rig has an icemaker or a washing machine, drain those lines too, following their manuals.
With the faucets open, connect a regulated compressor to the city-water inlet through a blowout plug and blow air through the system, one fixture at a time, until only air comes out. Keep the pressure low: 30 PSI is the widely cited ceiling for RV plumbing — never use unregulated shop air, which can blow fittings apart. Work fixture by fixture, and don't forget the toilet valve and outside shower. Blowing out does not replace antifreeze on its own (water can still sit in low spots and valves), but it gets most of the water out first, so the antifreeze that follows stays at full strength.
Set the bypass valves so antifreeze never enters the water-heater tank — otherwise you will fill a 6- or 10-gallon tank with antifreeze you then have to flush out in spring. Bypass systems vary: some rigs have one, two, or three valves at the back of the heater, and some have a single-lever bypass. Check your manual for your setup. Then remove the drain plug or anode rod and drain the tank completely. If your heater uses an anode rod (common on Suburban heaters), inspect it while it is out — if it is more than about three-quarters eaten away, replace it before spring. Atwood/Dometic heaters typically use a plastic drain plug instead of an anode rod; either way, leave the plug out or loosely in place over winter so any remaining water can escape, per your manual.
With the water heater bypassed, pump RV antifreeze through the system until it runs pink at every outlet, in this order:
Then pour about a cup of antifreeze into each drain P-trap (sinks, shower, tub) so the water sitting in the traps does not freeze and crack them. If any fixture still runs clear, keep pumping — clear water at a faucet means diluted antifreeze somewhere upstream. Pink at every outlet is the proof the job is done.
Take out any inline or canister water-filter cartridges and drain the canister. A filter left in place over winter can crack, and antifreeze sitting in a filter is a flushing headache in spring. Store the canister dry, and plan on a fresh cartridge before your first trip.
A fully charged battery resists freezing far better than a discharged one, so battery care is part of winterizing, not an afterthought. Full guide: What to do with RV batteries over winter. In short: if you have power where the rig sits, a smart maintainer is the easiest good answer. If you don't, disconnect the negative terminal so parasitic loads (detectors, radios, control boards) can't drain the battery for months, and check the charge every four to six weeks. Pulling the batteries and storing them somewhere above freezing, checked monthly, is the best shape you can leave them in.
Inflate to the pressure on the tire sidewall before storage — tires lose roughly 1 PSI for every 10-degree temperature drop, and a soft tire sitting in one spot all winter can flat-spot. Cover tires that will sit in sun, since UV ages rubber even in winter. If the rig will sit for months, moving it occasionally beats letting it sit on one spot all winter.
Wash the rig before covering it — grit trapped under a cover works like sandpaper all winter. Let it dry, then check the roof and window seals for cracks while you are up there; winter is a bad time to discover a leak. Put the cover on on a calm day if you can — wrestling a big cover in wind is a two-person job at best — and secure the straps and hem so wind can't work it loose. Full guide: RV cover buying guide: what fits your rig.
One fact about this site's owner: he put the cover on his Four Winds motorhome on October 25, 2026, ahead of winter in Utah.
Take out all food and anything that can freeze and burst (canned goods, bottled liquids, cleaning sprays). Turn the fridge off, clean it, and leave its door ajar so it doesn't grow mildew. Leave cabinet doors ajar for the same reason, and consider moisture absorbers inside for the winter. Close up gaps mice could use — steel wool in small openings, and a check for droppings when you visit — because a warm rig is exactly what mice look for all winter. Remove batteries from remotes and devices so they don't leak over months of cold.
Top off the fuel tank — a full tank leaves less room for condensation inside it — and add fuel stabilizer dosed per the label. Then run the engine and the generator long enough for treated fuel to reach them (around 10 to 15 minutes each is the usual guidance). Check the engine coolant's freeze protection with a hydrometer or test strips: it should be rated well below the coldest week of the year, not the average. Through the winter, many generator manuals call for running the generator under load periodically (often about 30 minutes a month) — follow your generator manual's exercise schedule rather than letting it sit untouched for months.
Winterizing isn't one-and-done. A monthly look costs ten minutes and catches problems while they're small: cover still secure after storms, batteries holding charge, no water where it shouldn't be, no droppings or nesting, tires still up. The expensive winter failures are almost all water left somewhere it shouldn't be, or a battery left to die — and both are caught by a check-in.
Tankless (on-demand) heaters don't have a tank to drain, but they still hold water in a heat exchanger — and they usually can't be bypassed the same way. Most tankless manufacturers call for circulating antifreeze through the unit with a pump kit, or for a specific drain-and-blow procedure, and some warn against compressed air entirely. If your rig has a tankless heater, follow its manual's winterizing section exactly and ignore the tank steps above. This is the single most common place where a generic checklist goes wrong.
How much antifreeze do I actually need?
For a Class C motorhome with the water heater bypassed, typically 2 to 3 gallons. Larger rigs, more fixtures, icemakers, and washing machines push it higher. The real answer is "until every outlet runs pink" — buy an extra gallon and let the pink be the judge, not the jug count.
Can I just blow the lines out and skip antifreeze?
You can, but most manufacturers and experienced owners don't recommend it in real winter cold. Air leaves water in low spots, valves, and the pump. Blowout plus antifreeze is the thorough method; air alone is a gamble.
What PSI do I blow out at?
30 PSI is the widely cited ceiling for RV plumbing, regulated — never unregulated shop air. If your manual states a lower limit, follow the manual.
Can I use automotive antifreeze?
No. Automotive antifreeze is toxic and not made for potable water systems. RV antifreeze is non-toxic, pink, and made for this exact job. If automotive antifreeze ever gets into the lines, the system needs a thorough flush before anyone drinks from it — and if in doubt, have it checked.
When should I winterize?
Before the first hard freeze — not after it. A single night well below freezing can split a fitting. In Utah cold, that means well before sustained sub-freezing nights arrive, not when the forecast first mentions frost.
Do I need to winterize if I keep the heat on?
Only if the heat is guaranteed all winter: a furnace needs propane and 12-volt power, and if either runs out, the pipes are unprotected. Heated storage with reliable power is a different situation from a rig sitting in a driveway with the furnace "probably" running.
Bottom line: drain everything, bypass the heater, pump antifreeze until every outlet runs pink, look after the batteries, cover the rig — and check on it through the winter. Work the list in order, and when anything on your rig differs from this page, your owner's manual is the one that wins.