What I ment was as low as possible but still above sea water level.
Most engine applications do have the header water manifolds
over the sea water level,and a 1" fall is enough
for the system to drain itself.
The water level in the headers can't exceed the sea water level
unless engines running.
We don't trailer our boats so much here in Sweden,
so one of the reasons I'm using this system is to
prevent hydraulicing in case of internal header leaks
I've been using it for 3 years,it works perfekt!!!
Cheap,easy,reliable.
Good luck!
Jonas.