Now obviously we are talking about black water dump seacocks and again obviously if you are using them as black water holding tanks, you should keep them closed in an anchorage.
But I know of lots of sailors that keep one closed and the others open and divide their, shall we say numbers one and two’s between them.
Despite your thoughts about this practice, having just had a rather nasty blockage in our dump pipe a long way up from the sea cock caused by sealife taking hold whilst they have been left open, what is everyones recommendations about this??
I go the 1 open for 1’s, 2nd closed for 2’s option.
The closed one give me grief when settled matter clogs up, the open one is fine, touch wood!!
This is what we do but it was the open one’s that blocked up and I”m pretty sure with sealife growth. It was a mission to dislodge but we got there in the end. Gotta love Marine heads.
My general practice is to leave things open offshore. This is I think clearly best for gravity dump systems. I’m open to thoughts on macerator systems but for now I keep those open also.
On boats with deck wash systems that actually have hoses (I’m a delivery skipper and move a lot of boats) when we approach landfall I make sure everything is empty (just happens with gravity, action required with macerator) and flush the tanks with the deck wash through the deck fill. When the valves are closed heading inshore the hoses are clean.
Some boats have a manifold at the tank in addition to the thru hull. That makes keeping sewage out of the overboard discharge tube simple.
I think more important than open or closed is exercising all thru hulls regularly and inspecting hoses for deterioration.