[C320-list] Repurposing head thru hull

[Troy Dunn]

I'm finally getting around to installing a washdown pump on Wonky Dog.   On
many hulls in the 400-600 range like Wonky Dog there is a single forespar
marelon thru hull beneath the head sink that has two barbs.  One of the
barbs is connected to the shower sump pump via a anti siphon and check
valve.   The other was originally connected to a anti siphon and then the
head.   We removed the seawater flush when we installed an electric head.
So now I have a "spare" barb.   I want to repurpose this barb to feed a
washdown pump.   I have two questions (well, maybe three).  1) Has anyone
else repurposed one of these inlets? 2) If I’m going to a washdown pump do
I need an antisiphion?  3) how does the two barb thru hull work?!   Why
doesn’t the head suck wind as opposed to lifting water through the seacock,
is it because the shower sump pump has enough resistance to not allow air
to flow through the pump?  Or is there some other reason I can’t think of
and will a 5 gpm pump overcome said resistance and function poorly?

Regards

Troy Dunn
Hull #514