Learn German: Unter dem Boden dürfte ein Rohr liegen. - A pipe is probably lying under the floor.

At this level, you will see modal verbs used "subjectively" to express how likely the speaker thinks something is. When dürfen is used in its Konjunktiv II form (dürfte), it completely drops the meaning of permission. Instead, it expresses a high probability or a strong assumption, similar to saying "is highly likely to" or "probably."

How certain is the speaker when they use dürfte compared to other subjective modals?

dürfte expresses a high degree of certainty, often around 80 to 90 percent. It is slightly less absolute than müsste or muss (which imply logical necessity based on hard evidence) but much stronger than könnte (which only suggests a mere possibility). It implies the speaker has a very good, logical reason to make this assumption.

Why is the subject ein Rohr in the middle of the sentence instead of at the beginning?

In German main clauses, the conjugated verb (here, dürfte) must stay strictly in the second position. Because the speaker chose to set the scene by putting the prepositional phrase Unter dem Boden in the first position, the subject ein Rohr has to slide to the third position right after the verb to maintain this rule.

As a quick refresher, why do we use the dative dem Boden here instead of the accusative den Boden?