Well, as stated I never use more than 10% methanol, which wont prevent it from freezing much below 32F, and higher percentages are dangerous.
Whats annoying in CA is they sell washer fluid that isnt methanol, and you dont want to use that in the washer tank either when planning a skiing trip.
A lot of the washer fluids are 99% methanol.
I dont use the garden hose. If I dont have a real cheap source of distilled water around, like 99 cents for 2 gallon jug at Wal mart, I will use it out of the filtered tap. Although I dont use that much water, like other guys. They must be using it from a hose if filling 30 gallon tanks. I just have a 5 gallon tank and one primary 200cc nozzle when boost is over 4psi, then a secondary 200cc nozzle for when boost is over 10psi. Water pressure between 90 and 130psi. Someday I might get it set up to start spraying at 2psi or so, which would make sense for highway cruising, then I would use more.