I want to put a utility sink in my garage. The main reason is to have softwater hot & cold for car washing etc. I plan on tapping into bathroom plumbing in the basement and run pipes up and through the firewall just above the foundation wall into the garage. I have easy access to the basement bathroom plumbing in an adjacent unfinished utility room. I know how to solder copper and PVC pipes etc but have never done any drain/vent plumbing. The toilet and sink vent are shared in sort of an 'h' configuration. There is also a shower drain which is probably connected to that venting as well but I can't see that. The toilet vent would be the easiest and closest for me. I don't care about finishing the utility room so the pipes can run outside the wall cavity.
My question is where to splice the drain for the utility sink? Can I splice anywhere into the basement toilet (2") or bathroom sink vent (1.5") stack without causing problems?
What measures do I take when passing the plumbing through the garage wall (firewall)?
Garage can get cold enough to freeze I plan on putting some kind of manual shutoff/drain valve in the basement, but I would prefer some kind of automatic (passive) system where the pipes drain back into the house each time the water faucet is turned off or not in use. Does such a thing exist? (I know about anti freeze hose bibs but I do not want to use those if possible).
Do anti siphon valves need to be permanently installed on the plumbing? Or am I OK just using an external add-on hose bib anti siphon valve attached to the sink faucet?
Thanks
Kevin