Looks like John and I have similar approach to water when boondocking. As mentioned, dish washing is a once a day at most, sometimes even go another 1/2 day, We have two 32 gallon grey and a 32 gallon black tank and DW and I can easily go 10+ days before those fill up. Our fresh tank is shy of 40 gallons, but I carry the 7 gallon blue jugs with us. Fresh water lasts us about 5 days, then I either pull out 4 full 7 gallon jugs, or fill at the campground. I have an extra onboard water pump with outlet plumbed into fresh water fill, inlet is a SS dip tube on hose, stuff the dip tube into the jug, flip the "fill" switch on the extra pump and fill fresh tank.
John's ball valves on bath sink is now on my "to do" list.