Replaced a cracked leaking bathtub in Rental Property for $6K - Repair or Improvement?

The unit was built in the early 1980s and the bathtub is original.  I bought the unit a few years ago and the bathtub was fine for a few years.  Last year it got a small crack and started leaking.  I tried to do an epoxy repair on it, which lasted a few month and then it started leaking again.  This year I went ahead and replaced it for about $6K.  How do I claim it?  Obviously I would want to calim it as a Repair if I can.

 

I asked Google Gemini, and it was convinced that I could claim it as a Repair, as I was fixing a broken fixture which is required to be functional (it is the landlord's responsibility in NC).

 

I asked Microsoft Copilot, and it was sure it was an Imprevement, depreciable over 27.5 years.

 

Which one is it?