Building a Sea Chest

[Caymanboy]

Sorry, went back to the first post.
My concern would be the supplys you have, appears they are either 3/4" or 1"? That would be a total of 1 1/2" or 2", is that enough to supply ALL three of those pumps when they are running? They are what, 1500-2000 GPH apiece?
The next thing to figure out is, what kind of p/u's do you have? If there is no scoop on them, the water will get pulled out of the box, if there is, water will be pushed into the box, all the time.