Most of the foot-pedal pumps are meant to be installed behind the cabinetry-- usually in the kick plate under the cabinet doors-- with the foot pedal itself sticking through. This usually requires a larger opening than you'd like to have. I made cute little cover plates to trim mine.
It is
vital that you mount the foot pump with two key considerations:
1. Mount it
very strongly. Your foot and leg are much stronger than your hand and arm. The Whale foot pump (Galley Gusher) is very powerful and pumps like crazy. But you can easily tear the pump off the wall if it's not mounted securely. I advise through-bolting this with 10-24 machine screws (the holes are #10 but can be enlarged to 1/4". Use large fender washers on the back-- and make sure what you're mounting it to is strong too!
2. Mount it so that it's
easily removable. These pumps can be serviced and if something bad happens you should be able to detach three nuts & bolts, detach two hoses, and take it right out with no more hassle than that. Don't hide or cover up the nuts & bolts so that it's a deconstruction disaster to try to remove it.
You are right to worry about fresh-water consumption. You'll need to practice washing dishes and rinsing your hair with as little water as you need. When at sea, ration the water by using a personal rinsing jug-- about 3/4 gallon-- to fill with fresh water and then
turn the water off. Bathe in seawater and use the fresh in the jug to rinse. Unless you've got really long hair or a skin condition this should work pretty well.
Consider using a particle strainer on the seawater line. This, like the toilet intake and engine intake, should be fitted with a proper marine seacock that's easily accessible. I advise a Forespar Marelon one, as you should never drink from bronze (assuming there is any reason you might consume some of the seawater). Use drinking-water-safe hose (clear with blue tracer). Don't 'tap in' to something else, like the saltwater washdown or the toilet intake. We tried this on a past boat and soon enough the seawater at the faucet began to stink...
bad. All the other service on that line was dirty water, lying in the hose in the bilge. Ugh. It's not a problem to install one more inlet and seacock so long as you take the care to turn it off and on when you should.
The seawater won't need any special faucet-- actually, since you're not drinking it, it can use anything, like one of the cheap aluminum Whale 'Tuckaway' style. Aluminum is not strictly FDA approved and aluminum leachate (such as from soda cans) has been tenuously linked to Alzheimer's (hence the date codes on soda cans--
not there for 'freshness'; there to avoid
liability suits). But most people may want to install something prettier, and for that it's drinking-water-safe chrome-plated brass, like in your house.