Pure water.  It won't freeze until temp hits 32F or 0C.   You want
colder?  Buy the pink (non-toxic) rv antifreeze.  But don't drink it.

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To winterize *most* rigs the right way:

DRAIN water tank & water heater

BYBASS water heater

CONNECT pump inlet via hose to jug of pink stuff (use tee/valve)

PUMP AF into pipes 'til it comes outa faucets (and shower, toilet)

DUMP holding tanks

For more detailed, illustrated winterizing information see
Les Doll's Painless Winterizing, at The RVer's Corner,
<http://www.rverscorner.com/articles/painless.html>.

In very mild climates you can get away without winterizing at all.
Some get by using compressed air, a few by just draining.   But
if you want to be fairly sure of NEVER having to fix split plumbing
parts, the above system is as easy and foolproof as we know about.

NOTE:   When "un-winterizing", flush the pipes with water BEFORE
placing WH bypass valves back to normal.  That way you won't flood AF
into the water heater, and one flush is good to get rid of the pink.

Will - The self-appointed Curmudgeon of Sill Hill

Dunno about least taste but a gallon of good whiskey will do the job
and requires no cleanup!

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$$$$$$$$$%%
Yours truly, Johnny Dollar!

Everclear.

No aftertaste, prevents freezing when used in sufficient concentration,
disinfects, and is only toxic to teetotallers and some diabetics. <VBG>

A 50/50 mix works well when used throughout the Fresh Water System.