Anyone have tips on tracing lines?

I'm trying to (finally) install the water softener and I literally have NO idea where my pipes are going. There's already a bypass in place, but the bypass valve is broken, so I can't tell which faucets it controls. Anyway, just looking at the lines to see if they're alright to use, I have absolutely no idea what's what. I'm thinking it wont work since lines are branching off left and right, and it looks like our main goes from one room to the crawlspace so it's hard to figure out. This is frustrating. I have no idea how you guys do this.

Looks like i'm gonna have to call someone to come out here and do it properly, which I should have been able to do myself and will cost a ton of money.

As you might already know, you want your incoming line to feed your outside spigot/s before your water gets to the softener, then your water heater and everything else following the softener. To locate your incoming line, find the one that begins feeling coolest first while water is running in your bathtub, then use the same technique to locate the line/s to your outside spigot/s by letting it/them run for a bit.

pip[ing

I put valves on BOTH lines and the bypass. That way, I can tell which line is the feed to go into the softener, and also what the softener will service by shutting them off.

Have that same setup, but cant tell whats what because the middle bypass valve is broken. So whether it's open or closed it'll work the same.

Can't you replace the valve?

I guess, but that would cost me about $100 since I have nothing needed to do it and i dont even know if it's set up right. That's what sucks. If i knew that the setup worked the way I wanted but only the valve was messed up I'd have done it in a heartbeat. Arghhhhhhhh!

You HAVE to replace the bypass valve anyway when you install the softener, otherwise the water will just flow through it instead of through the softener.

I was just going to use the softener mounted bypass.

valve

You still have to do something about the broken bypass valve. Either fix it or remove it. Since I have had softener manifolds crack, (one just last month), I prefer NOT to depend on the softener's bypass valve.