Building a plumbing system from scratch? On demand LP heater

[Svenn]

Hi All,

I was looking for some advice in building a total freshwater plumbing system from water tank to showerhead using an on demand propane water heater. I'd like it to be freeze tolerant (assuming I have to empty it) when unoccupied. Around 30 gallon tank and I have both 120v and 12V available.

I'm looking at an Atwood heater since it has a freeze protection package, but I can't find any water pumps, hoses, showerheads, faucet handles that do as well. Each piece of the project seems simple enough looking at the user manuals, but I feel like it's one of those things where general advice/recommendations is warranted. Thanks!