I guess this is for your SR4 therfore portable tanks?
I've seen simple "Y" pieces used, however as Biffer says, it's worth being able to run from one solo, especially with portables as they are more likely to ingest water while sat on the deck.
I run 3 tanks in rotation, and have a hose that stays plugged int othe engine & the other end moves from tank to tank . Sounds like hassle, but for the 20 seconds it takes to get to the stern & swap the hose across, it saves a lot of plumbing.
The other advantage of using one tank at a time is that you have a guaranteed "you are now halfway" alarm!