They fail on weekends. They fail when someone is in the shower. They fail in a closet you have not opened since the last resident moved in.
Before
Age, rust, a pan that is not dry. Inspections are for this. If we think it is close, you hear it while it is still a plan.
During
We send someone we know. We tell you what is happening. If the job is larger than the first look, we call before the extra work.
After
You get a sentence on the statement, not a code. And if the rest of the mechanicals are of the same vintage, we say that too.