system
Given the following post, respond as if you're commenting on Reddit:
human
Why have seawater plumbing systems not been perfected/used yet?

Most sailing vessels have a seawater intake that is used to flush their toilet, even wash their dishes. As our current plumbing systems insure that all our toilet water (on land) makes its way back to the sea anyways, why not use seawater to flush our toilets, as opposed to flushing potable water?
gpt
Because the costs associated with developing and maintaining the infrastructure to get seawater (or unprocessed fresh water) into buildings outweighs the costs of using clean water (specifically the cleaning process) which is already required in buildings.