Had to install a new septic system at my rental house last year. Is this considered an expense that can be taken in one year or does it have to be depreciated?

[ThomasM]

The IRS considers a septic system to be a capital improvement rather than an expense.  So you'll depreciate it over 27.5 years rather than deducting it.

Here is a link to IRS Publication 527, Residential Rental Property, which discusses all aspects of this topic.  Note table 1-1 beginning on page 5.

https://www.irs.gov/pub/irs-pdf/p527.pdf