April/MAy 2018 9Steve D’Antonio responds:
Jim Lawrence makes some useful
and interesting points regarding the
benefits of muffler drains. It’s wise to
drain a muffler during extended crank-
ing, as well as for dealing with potential
flooding from a following sea. I am,
however, cautious about leaving this
drain open, for fear that a siphon
(which should not be possible with a
properly set up siphon break) could
lead to flooding. He notes the precau-
tions he takes to prevent this, which are
commendable. For more on antisiphon
valves see https://www.proboat.com/
2017/06/antisiphon-valves/.
The valve installation, with its pro-
tected location and support, also sounds
reasonable, but the material chosen for
the valve itself is of some concern.
When it comes to raw-water plumbing,
with rare exceptions I’m not an advo-
cate of PVC or CPVC. In addition to
lacking the necessary tensile strength- During situations of concern about
following big seas filling the exhaust sys-
tem from the exit on the transom, there is
no need to close a seacock in the exhaust
line and for the captain to remember (or
the crew to know) to open the seacock
in the exhaust line before cranking the
engine. Again, opening the small drain
valve on the muffler to the bilge can pre-
vent small accumulations of seawater in
the exhaust system over a long period of
time from creating an unexpected cata-
strophic situation at a most inconvenient
time—like a man-overboard event.
Over the years I have seen a couple of
drain valve installations on other sail-
boat exhaust systems, but I have never
seen anything in print about them. Are
there any potential downsides or issues
with the sailboat exhaust-system drain-
valve installation described above?
Jim Lawrence
S/V Seamist
Panama City, Florida
so that the valve was generally protected
from being a step or trip hazard, and the
handle of the valve is easily accessible
from inside the engine space and easily
seen from outside the engine space.
The benefits of a small drain valve in
a hydro-lift muffler are twofold: - During repeated attempts to crank
the engine, it is not necessary to close the
seawater intake, potentially running
the water pump dry for extended peri-
ods. In these situations, I prefer to open
my drain valve and dump the seawater
into the bilge, allowing the sump pump
to remove the water. After successfully
cranking the engine, a small amount of
exhaust gas will leak from the open
drain pipe, so be ready to close the valve
or shut down the engine. If by chance
I forget to close the drain valve after
cranking the engine, the sump pump
buzzer alerts me, and if this situation
continues, then the bilge pump is acti-
vated and the associated alarm sounds.
Letters172-ADFinal.indd 9 2/21/18 8:12 PM