Difference(s) of holding tank, grey water tank and black water tank?

Question

I am approached by a salesman that the boat I am going for should be installed with a holding tank, a grey water tank and a black water tank so as to keep the aquaworld clean. I totally agree with it. However, I know what a holding tank is for but I am not sure the difference of holding tank, grey water tank and black water tank. Can anyone advise me? Thanks.

Answer 1

Holding tank is a general reference to a tank collecting liquid waste to avoid direct discharge overboard.
In common usage, holding tank equals black water tank (meaning waste from the heads of the boat, i.e basically human waste).
Grey water refers to water from sinks (heads sink and/or kitchen sink, i.e. usually dirty water that have detergents content etc).
i.e. - there are actually only two types of tanks, not three.
Holding tanks, be it for black or greywater have Y type valve which is closed in marinas and inshore waters, but allow direct overboard discharge while sailing offshore.
In some marinas there are facilities to empty holding tanks through special pupms. Otherwise you need to go offshore to empty them (different countries have different rules, while some countries do not require the use of holding tank at all).
In USA: discharge of raw sewage from a vessel within the three nautical mile limit of U.S. territorial waters is illegal, (the Chesapeake Bay and Puget Sound are considered to be within the three mile limit). For boaters, this means that any direct flow-thru systems must be secured while a vessel is navigating inland waters or within three miles of shore.

Answer 2

Your gray water tank holds waste water from your shower and sinks etc. Your black water tank holds sewage. It's illegal to blow your black water tanks if you're less than 12 miles out from shore.

Thinking it through some several hours later. I may be wrong about how far out you must be to discharge, check with the Coast Guard on this... Sorry if I gave you any misinformation.