If this were a toilet, would the installation be completed when it was not yet hooked up to the water lines and sewer?

Section 25D(e)(8)When expenditure made; amount of expenditure

(A)In general

Except as provided in subparagraph (B), an expenditure with respect to an item shall be treated as made when the original installation of the item is completed.

(B)Expenditures part of building construction

In the case of an expenditure in connection with the construction or reconstruction of a structure, such expenditure shall be treated as made when the original use of the constructed or reconstructed structure by the taxpayer begins.