What is the name of the episode where Tony and Carmela separate?

The episode where Tony and Carmela separate is “Whitecaps,” the fourth-season finale of The Sopranos.

The separation begins after Tony's former mistress Irina Peltsin drunkenly calls the Soprano home and tells Carmela about Tony's affairs, including his relationship with Svetlana Kirilenko. Carmela throws Tony out and confronts him about years of infidelity, while Tony responds angrily to her accusations and to her admission that she has feelings for Furio Giunta.

Tony moves into the Whitecaps property, a Jersey Shore house he had planned to buy for the family. The title refers to the house and also symbolically evokes rough water, reflecting the turbulence in the Sopranos marriage. Tony ultimately abandons the purchase after antagonizing the owner, Alan Sapinsly.

The separation does not become permanent. Tony and Carmela reconcile during the fifth season after Tony agrees to buy Carmela an investment property in Montville. Their marriage remains deeply damaged, but the couple reunites before Tony is shot by Uncle Junior in season six.