Newbie question about water softener installation

[vj.diy]

I’m trying to install a water softener in my garage, I’m confused with few things with the manabloc and if I am doing the right thing.

The manabloc in my garage have what appears to be two cold water line, I’m hoping the one with the bigger diameter (PVC) is the cold water inlet and the PEX blue one is the outlet from manabloc to water heater. Is my understanding correct?



I also see a gray PVC cap on the garage wall, does this indicate there is a drain behind it that I can use? Need to run the drain pipe from garage to laundry room through a wall, adjacent to garage otherwise.




Two of the professional plumbers I consulted indicated that there will be a “T” that brances off prior to Manabloc to heater, is that even accurate? Every manual and search about Manabloc indicates the main water line will reach to one of the inlet in manabloc.

This will be the first time I will be doing any plumbing work so being a little cautious that I don’t flood my house and have my wife yell at me for my escapades

 

[TomFOhio]

Do you have a water meter or are you on a well. If you are planning on softening all the water this is usually the area where the softener is located.

 

[vj.diy]

I'm on city water.
Am I right in guessing the drain line and is the line with bigger diameter is where i should take the inlet for water softener?
Do I need to add p-trap before attaching the drain to the drain pipe located in the picture?
I was hoping to attaching a "Sanitary Tee" before the drain cap, is that recommended?