Olivone only had a single rather smal black water tank apr. 48 liters, which lasted about one week for two persons. We decided to install a second tank under the forward bunks (there was no room to expand the existing tank). But the original tank had a clever design, first of all it has a cone shape and both the possibility to empty direct to the sea or the possibility to empty through deck fitting
To keep the functionality of the origninal tank and at the same time expand the system to a second tank we decided to fit a coupe of extra outlets-inlets to the existing tank and two macerator pumps, one for empty the old tank into the new one and another pump to fill the old tank from the new without making any new thru-hull-fittings.
We did use up a lot of santitation hoses and ball valves, we wanted to be able to completely shut of the different connections at strateci points to be able to swap pumpe etc.
The extra tank is also a clever one where you can choose which size of tank you want and the cap with the hose connections remanins the same.
What you dont see on these pictures is the plattform i had to build for the tank between the bulkheads to get a flat surface to put the tank on. All in all it was a pretty big job to take out the old tank and weld on new hose fittings and as you all know there is not much space to do this kind of operations on a boat and i had to make a new lever for the ball-valve (first picture) since the standard lever would not fit. But in the end im rather sattisfied with the result and now the black water tanks will last two weeks for two persons. The cost for this was about 700 Eur in parts and a lot of work.
Here is the control panel for the macerator pumps.