I dont know about drip water changes for marine tanks. Ive only ever seen it on freshwater tanks. But what most reefers will do is utilize dosing pumps such as the apex dos and have it change out certain amounts of water at certain periods of time. For example one user on here has his apex run, I believe, 1 cup every hour. Or something like that.
A pure drip system would be really difficult to implement. You've already got to top off water to deal with to maintain salinity, adding a drip system like FW tanks have would wreak havoc.
A lot of reefers use an Automatic Water Change system instead. I personally implemented one using a dual head peristaltic pump. One pump draws water from the first chamber in my sump and dumps it down the drain. The other draws water from a 55 gallon drum full of premixed SW and pumps it into the second sump chamber. Mine runs for 15mins, once a day and changes about 3 gallons of my 240g total volume.