Laundry room remodle

I am remodeling our laundry room. I plan to replace the existing concrete 2 bowl laundry tub with a new fiberglass two bowl tub. I have several general plumbing questions: I want to install a "valve box" for the washer connections. I am also planning to run the supply plumbing for the laundry tub behind the wall. Can I use the same air chamber for both sets of valves or do I need an air chamber for each set? Currently one set of air chambers exists (one for hot and one for cold) but both the faucet and washer connections are connected vertically in series. With the new plan the valve box will be 12" offset from the planned new laundry faucet supply lines. Also is it ok to replace the old galvanized waste line with a plastic pvc line into the main drain?

remodel

AIr chambers, when they work, are best installed at each fixture. But since they are seldom used anymore, and have a limited lifetime of actual service, anything you do will work until they fill with water and lose their functionality.

As hj mentioned, air chambers were a "good idea at the time" but have prooved to be effective for only a short period of time, and then become a place for water to stagnate and cause problems. You should get actual hammer arrestors ( the kind with rubber bladders) and install one set, or a set at each fixture. Sioux Chief makes them and others as well.