No permit was pulled--problem with resale?

[Bienes Raices]

I'm waiting on a short sale to come through. The seller told me he replaced the sewer line (with PVC) without pulling a permit.

I'm planning to rent the house out first (for years). When I eventually sell will I have to disclose that the sewerline was unpermitted since I now know about it? Could this cause a problem with the eventual resale or with the future buyer's lender? Could I be forced to have the work permitted or redone? Thanks.