Bilge Pump Drain Hose Routing...
This may be a dumb question, but here goes:
Bilge pump hoses generally have long lengths of drain hose routed to their own through hull fitting on the side of the hull above the waterline. Which often results in a significant quantity of water that rolls back down the hose and into the bilge after the pump shuts off. And gate valves to prevent this backwash are highly discouraged due to potential blockage issues.
So why don't boat builders utilize one of the existing through hulls that are under the water line already (like from the head or galley sink) to expel the bilge water? At least in my boat, for the cost of a simple pvc Y-fitting. This would result in a bilge pump drain hose that would be less than half the length that it is now. It would only have to pump/push the water half the vertical height that it does now. It would eliminate things like bilge drain staining on the side of the hull. And I'm "assuming" (maybe incorrectly), that since the sinks don't have siphoning effect issues, this would be eliminated too. So why not?