Breakdown of Die Arbeiter hatten das Leck bemerkt.
haben
to have
bemerken
to notice
der
who, which, that (relative pronoun; die, das)
der Arbeiter
the worker
Questions & Answers about Die Arbeiter hatten das Leck bemerkt.
Why does the sentence use hatten ... bemerkt instead of haben ... bemerkt?
Hatten ... bemerkt is the Past Perfect tense (Plusquamperfekt), which translates to "had noticed." You use it when you want to show that an action happened further back in the past than another past action (for example: they had noticed the leak before the pipes burst). If you just want to say they "have noticed" or "noticed" it, you would use the Present Perfect (haben ... bemerkt) or the simple past (bemerkten).
How can I tell that die Arbeiter is plural here?
Why use bemerkt instead of gemerkt?
Bemerken means to notice or perceive something externally with your senses (like seeing water escaping). Merken is more about an internal, mental realization or remembering something. Also, notice that bemerken starts with the inseparable prefix be-, which is why its past participle (bemerkt) doesn't get the usual ge- at the beginning!