[jz638]

Urinals use a lot less water for flushing, don’t they?

aircraft carriers don't use water, they displace water.

all kidding aside, it probably is less efficient on the non-potable water system to use toilets where a urinal would do, but even on aircraft carrier scale, it's not a significant concern when the vessel can filter new non-potable water as needed.

[msrngtp2002]

Navy ships use salt water for flushing