Frasier tells Roz at KACL that he is hosting a wine tasting that evening.
Later at home, he and Niles discuss and prepare for the tasting/party, now inexplicably occurring the following evening.
Bruce asks Niles if there are any bathrooms that aren't occupied, but the water's still turned off so he wouldn't be able to use it anyway.
Frasier needs to shave before his party, but the water is turned off. He apparently shaves without water, judging by the bits of facial tissue stuck to his face. However, Frasier always has bottled mineral water on hand, which he could have used for shaving.