This is another thing on my boat that I dont know what it is or its function. This is on the bathroom. The toilet has a macerator but dont have a holding tank. The only tank is the one on the picture. Also it has a swith on the bathroom wall, I dont know its use. Another question I have is, If this boat originally comes with a holding tank and where it is located.
The holding tank (if there is one) would fit aft of the potty against the port side hull next to the port side engine and just aft of the single battery. Mine is located there and holds approx 25 gallons. It also has a Y valve located just forward of the holding tank that directs the flow into the holding tank or overboard. I have a different potty that doesn't include that little tank.
Just a guess, but that looks like a holding tank of sorts. I think I see a valve before it to direct waste to the tank or overboard. Since it's higher than the head I suspect that switch is a pump. Looks like a DYS project so just follow the lines for the sure answer.
It is a 2-gallon Lectrasan salt tank. When that type of treatment unit is used in fresh water it requires a source of salt to make the wastewater electrically conductive.
Manufactured by Raitan Engineering, Millville NJ and in Ft Lauderdale, Fl. I have had very good customer service with this manufacturer. Google them for more info.