My new-to-me O'Day 272 has built-in side tanks for water and waste. I bought a manual to research these tanks, but it referred to other tanks, which were installed under the settees. I have heard that other classes from the same production facility have similar tanks. Can anyone help me with understanding the piping, cleaning, lay-out, etc. of these tanks? Why, if there is a waste tank on the starboard side, is there a vinyl flex tank under the v-berth? How can I empty it at a pump-out?