- - In the USA - gray water - sinks and showers are considered legal
to plumb directly overboard
. I don't know of any manufactured vessel that routes gray water to a holding tank
. Normally your sinks go directly to a thru-hull right below the sink. I have been in aggressively patrolled "No-discharge" anchorages
and the "ranger" was only interested in the plumbing
from the MSD to the holding tank via a lockable 3-way valve to avoid over-board discharge. And the valve had to have provisions for a padlock - which I thought rather silly as I have the key. But that's bureaucracy . . .
- - ** But do not remove your holding tanks! You may find that the composting head
does not work as expected or that you have to sell the boat in which case you will need to re-install the original style MSD and plumbing.