new injector hose leaking badly

I have replaced a leaking injector hose with a complete new assembly. Now water is pouring out of the square plastic piece. Why? Could the supply lines be switched at the wall connections or is something else wrong?

i just replaced the injector port assembly an hour ago and had the same result…i found some advice from a couple years ago that said to just eliminate the port and use a straight hose.thats what i was thinking too.that’s my new plan this weekend.no reasson it shouldnt work.