The shower drain pump and the bilge pump share a thru-hull on my boat. They are joined with a T fitting. I am guessing that this is not optimum. I am thinking they should have dedicated thru-hulls. Issue is I already have plenty of holes in the transom. 2 cockpit drains, 2 propane locker drains, 1 exhaust and 1 bilge. What say the crowd? Keep the T or drill and other hole? Shoulda made this a poll..... RT