A trick to save on water when cruising is to make all forms of water as available to you as possible. Salt water is by far the most plentiful water an ocean cruiser will come across, why not use it!
When doing chores like washing dishes or brushing your teeth, you are probably going to use fresh water from your tanks. This is fine, but that water is the only water available to drink and keep you alive. The dishes and your teeth don't actually care how fresh the water is as you scrub them clean, the only time fresh water is actually needed is at the last stage, the final rinse for the plates.
Now, you could easily grab a bucket and haul up some sea water from the side and use that to clean your dishes. Truth is, this is a lot of effort and the tap is right there on the galley sink! In the end, the sea water is present but never used because the tank water is easier to get at and thus will be used for superfluous uses.
To avoid this problem, the sea water needs to be as easy to reach as the tank water. This means that you should have the same water pump setup for the fresh as well as the salt water sides. If the fresh has an electric pump and the salt has a manual pump, the salt will still go unused!
In our case, the fresh water pump is a 2 gallon per minute electric pump. Therefore, the saltwater pump is the same sized 2 gallon per minute electric pump. I tapped the salt water plumbing into the hot water side, making it equally easy to use salt and fresh in any part of the boat.
It is important to make sure you install a valuing system though, that way salt water can't backfeed into your fresh supply and destroy all of your drinking water!
When washing dishes in the galley, the hot tap is now salt and the cold tap is now fresh! I can scrub and wash until my heart is content with all the salt water I want, and then at the end, I rinse all the dishes together with fresh water. This lets me finish the dishes with a fresh rinse and use much less water than I would have if I washed everything with fresh.
With brushing your teeth in the head, the salt water is all you really need! The hot tap is salt, so you can wet your brush, scrub them clean and then rinse with salt water. Seawater is actually very good for you gums and you don't need to rinse with fresh (unless you can't stand the taste of salt). As a dentist, one of the treatments for people with severe bleeding gums (gingivitis) is to rinse with salt water after they brush because the salt water helps their gums heal faster! Why not take advantage of this on a daily basis while out at sea!