plumbing in heads and seacocks


Hi all, got a little question: I'm fitting a toilet into my boat and I
am finding places to fit the inlet and outlet seacocks difficult.
The best position is with the outlet below the inlet and about 18
inches apart, but should the outlet be above the inlet to help prevent
sucking back in what you have pumped out? The fitting diagram shows
that but there is no mention of it.

Is there a normal spacing apart of these seacocks?

Help really appreceated;


Pete
.