The defender has come right through the youth system at Melwood.
Pinnington, 18, recalled to liverpoolfc.com: "It feels like home.
"I spend more time here than I do at my actual home. I'm still excited to come every day and it feels like a second home.
"We've had some good trips over the years, quite a lot. The best one I'd probably say was when we went to New York. That was a good experience.
"I've been a ballboy for quite a few games over the years. The best one, I always remember it, getting up and running down the line to the other ballboys was when (Divock) Origi scored that last-minute winner against Everton. That was the one that sticks with me the most."
Pinnington added, "The aim? Obviously I want to be playing at the highest level that I can. Hopefully that's at Liverpool. If it's not, the highest level I can get to."