I was on an AS 738 flight from SEA-EWR back in April where all the lavs stopped working. It was a new 738 that AS had just taken delivery of and the lavs stopped working right after I went. We were somewhere over Montana and the pilot announced that we had to return to SEA. So we ended up going back to SEA after having been up in the air for about 1 hour 30 minutes. Sure was not fun flying for 3 hours and getting nowhere.