RV Winterization Antifreeze Calculator
Stop guessing how many jugs to grab. Answer a few questions about your rig and we'll itemize exactly where every gallon goes.
1 · Your rig
This estimates quantity only — always follow your RV's owner's manual for the actual bypass valve locations and draining sequence, since those vary a lot between manufacturers.
2 · How much to buy
Buy at least one extra gallon beyond this total. RV antifreeze is cheap — a jug or two — and running short partway through in freezing weather with wet lines is a much worse afternoon than having leftover antifreeze for next year (it stores fine).
How the math works (every line item, no hand-waving)
- Base gallons by rig size: Small = 2, Medium = 3, Large = 4.5 — a rough proxy for how much plumbing line has to be charged end to end.
- Extra fixture sets: +1 gallon for each fixture set beyond the first (so 1.5 sets = +0.5 gal, 2 sets = +1 gal).
- Water heater: if you're bypassing it, this is $0 — you only drain it, you don't fill it. If you're not bypassing, we add the tank's own volume (6, 10, or 16 gallons) since it must be completely filled with antifreeze instead of just drained and air-blown.
- Ice maker: +0.5 gallon for its supply line.
- Washer/dryer hookup: +1 gallon — a residential-style washer has its own fill lines and trap that need protecting.
- Outdoor shower/kitchen: +0.5 gallon for the extra exterior run.
- Total is rounded up to the nearest half gallon, since jugs come in whole/half-gallon-friendly sizes and rounding down risks coming up short.
- This assumes the conservative all-antifreeze method (no air blow-out first). If you blow out your lines with compressed air before running antifreeze, you may use meaningfully less than this estimate — see the FAQ below.
Gear that pairs with this calculator
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FAQ
Do I need to winterize if I have heated tanks or live full-time in a cold climate?
Heated tanks and heat pads protect the tanks themselves, but they don't reliably protect every foot of pipe, every low-point drain, or every fixture in the system — a single hard freeze on an unprotected line can split it. Most full-timers in genuinely cold climates still either winterize fully during any extended cold snap they won't be actively running heat through, or they run a continuous heat source and accept the risk. If you're leaving the rig unattended and unpowered for any stretch of freezing weather, winterize it the same as if you were storing it — a cracked pipe found in spring costs far more than a jug of antifreeze.
What's the difference between RV antifreeze and automotive antifreeze?
They are not the same product and must not be substituted. RV antifreeze is made from propylene glycol, labeled for use in drinking water systems, and is practically non-toxic. Automotive antifreeze is made from ethylene glycol, is genuinely toxic if ingested, and must never be put anywhere near a system you'll drink from, cook with, or shower in. Always buy jugs specifically labeled "RV & Marine" antifreeze — the color (usually pink) is a visual cue but is not a substitute for reading the label.
Can I use less antifreeze if I blow out the lines with air first?
Yes — many RVers blow out the lines with compressed air (typically 30–40 psi through a blow-out plug in place of the city water inlet) before running antifreeze, which clears most of the standing water out of the lines first. This can meaningfully reduce how much antifreeze it takes to fully charge the system, since you're topping off already-mostly-empty lines rather than displacing full ones. This calculator's estimate assumes the more conservative all-antifreeze method with no air blow-out first; if you blow out the lines, treat this number as a comfortable upper bound rather than the exact amount you'll use.
Should I bypass my water heater or fill it with antifreeze?
Bypass it if you can — nearly every RV water heater has (or can have added) a bypass kit, and bypassing means you only need to drain the tank and never fill 6–16 gallons of it with antifreeze you'd otherwise waste. If your rig doesn't have a bypass valve and you don't want to install one, you can still winterize by filling the water heater with antifreeze along with the rest of the system, which is exactly what the "not bypassed" option in this calculator accounts for — just budget for the extra gallons.