The catridges are that way on purpose. It is a lot easier to turn the shaft 180 degrees than to rip out the walls and replumb the area that is backwards.
I fix them with the owners permission.
Sorry, I thought maybe you didn’t know it was only a two minute job. :eek:
(That’s what I get for thinking) 
But it is true, after handles are marked wrong OR turn the wrong direction to turn “off” and left that way for a while, it does take some getting used to when corrected.
Sorta like walking into a room and flipping on the light switch when you know the power is off.
Personally, I wouldn’t touch one during an inspection without a warning to the customer.
Every time I’ve ever thought “heck, it’s a piece of cake” something went wrong.
Why is this conversation still dragging on?
because someone alway replies…sorry.
Sorry
:mrgreen:
and if you don’t grease the stem you may roll the o-ring out of it’s channel causing an incorrect fit and leak. 
i had a re-fried bean buritto last night, and i think i rolled my o-ring this morning. ooooooooooooooohhhh maaaaaaaaan.
But here in America, hot is on the left and cold is on the right. So if “you only have to remove the handle and rotate the ‘center stem’ part of the cartridge (or the handle) 180° to change cold/hot to left (or right),” then wasn’t it installed wrong, seeming to indicate that, yes, it can be installed wrong.
Of course, this close to the border here, I find lots of hot/cold reverses because that little ol’ “C” on the cold means “caliente”, or “hot,” in Spanish. And since hot burns, they tend to reverse them so that the little ones under that the “C” means “caliente” which means “hot.”