What do I say in a letter to the previous homeowner, asking them to pay for basement water leak repairs?

I bought a home that was not disclosed with a leaking basement. Owned home only 3 weeks when the walls started leaking after a rain. Home inspection did not show anything because the basement walls were paneled. I had to tear down the paneling to find were water was coming from. The title company gave me old homeowners new address. I got 3 bids for repairs. What should I say in the letter? Do I get the work done first and ask for payment? Wait for an answer first? I dont know what the next steps are I should take. Thanks