One of the things we added before heading out was a raw water washdown at the sink. While this may not sound necessary, let me assure you that after extensive testing, our single biggest use of fresh water has been dish washing.
Our boat holds 85 gallons of fresh water, which if you take out dish washing, can last us over 1 month. Keep in mind also, that as of 2004, fresh water in places like the Bahamas is currently going for $0.35 - $0.75 per gallon.
With judicous use of the saltwater washdown, we can get a full load of dinner dishes completely clean in less than 2 quarts of fresh water. Keep in mind, once out here, you will be washing dishes at least once a day. That means if you are doing a fresh water only wash, you are using at minimum 2.5 gallons per day just to wash the dishes.
The point being, that regardless of how much fresh water you can carry, dish washing can quickly use up over 15 gallons of your available fresh water per week.
On Dream Catcher, we used a high pressure deck washdown pump mounted right below the sink to pre wash all of our dishes. The pump is plumbed into a seperate thru-hull that also supplies one of our air conditioner's with cooling water. This unit draws a whopping 8 amps when in use, but the usage is so sporadic and quick that really we don't notice it.
Admittedly, a pump this size is overkill, but the mega high pressure that we get from our setup makes quick work of cleaning out things like sticky bread pans, or slightly overcooked muffins or burnt rice.