Building Repair Deductions - Thirty Per Cent Of What?

"All the toilets together perform a discrete and critical function in the operation of the plumbing system" is the best line that I could find in the ninety odd pages of Regulation 1.263(a)-3 Amounts paid to improve tangible property" commonly known as the "repair regs".  Oh well. I read Tax Court Summary Opinions, the reality TV of the system, for the laughs.  I've been studying the repair regs for practical utility.  I have some observations that may be useful to people working on returns a...