Today on my flight from DCA to PHX they locked the bathrooms departing until we got to 18,000ft, and again landing at 18,000ft. They also had one bathroom out of service. About 45 minutes from landing they announced if you need to go, do it now, we locking the bathrooms soon. It was comical to see everyone standing in the isles waiting

Is this a technical issue with the plane, or are they locking the bathrooms to keep anyone from getting up when the plane is below 18,000ft? The FA said the plane needed to be at 18,000ft for the lavatories to work, which I have never seen before.

Edit.. and no I am not mad and don't want a credit or anything.. just curious :-). Overall excellent service on the flight... (two flights in a row with awesome FAs!)