Which is located.

Hi there, You wrote the same thing twice.

“Which is located” emphasizes more on a passive voice.

You can omit 'which is' and just say 'located' : 'If you require additional supplies, these can be obtained from the storeroom (which is) located in the second floor annexe.' It sounds better with 'which is', but is quite acceptable without these words.

that's a great question :)