I have a water-filled punching bag that I can't use with sand (various reasons, but mainly rodents, this bag also can only be filled with water). It's 55L when full.
I'm looking for ways to prevent it from freezing during the winter while still using it. The lowest temperature registered in Vancouver, Canada is -17 celsius, so I'm looking for some anti-freeze liquid that won't cost a fortune, that I can keep in the bag many years (so summer + winter) and that doesn't corrode vinyl, which is the inner material of the punching bag.
What are my options? What anti-freeze liquids are safe for Vinyl? Would salt be safe? Given the price of some options, I would be ok replacing the punching bag every X years (e.g. every 5)
What I found so far is (all prices are canadian dollars):
Star brite Bio-Safe Non-Toxic PG All Year Anti-Freeze
This gives -20 degrees celsius protection. I don't know if this is safe for Vinyl or if it will last many years: http://www.starbrite.com/item/bio-safe-non-toxic-pg-all-year-anti-freeze-coolant-full-strength
Windshield Washer Fluid
This is what was recommended to me by the company producing the punching bag. I found this: https://www.napacanada.com/en/p/RCE49304W# I don't know how much I should dilute it (what percentage of water) and I'm also terrified of filling it myself: I need to use mask, gloves and eye protection (all stuff I don't have) and I have no idea of how to dispose or where to store the excess. I would leave it outside but I'm afraid of damage it could cause to the property or to the sewers if I disposed through that. I would be happy to pay someone for the work, but I don't even know what kind of store would do such a thing.
Winter Washer Fluid - different brand
https://www.amazon.ca/nextzett-94252015-Anti-Frost-Windshield-Concentrate/dp/B004PGS368/ref=sr_1_1?dchild=1&keywords=Winter+Windshield+Washer+Fluid+Concentrate&qid=1635655664&sr=8-1#productDetails I also noticed it's made of ethanol. Could I just buy ethanol instead? The company said not to use alcohol because after a certain time it will eat the vinyl.