My understanding, in a nutshell, is that "black water" comes from the
toilet, and "grey water" comes from the sink.

Bobsprit wrote:

When looking through specs on very large cruising yachts I see the terms
referring to "black and grey" water in addition to regular fresh water tankage.
Can someone explain-is this tankage for not potable use, such as heads and
such?

Thanks!

RB