Seacocks

Tech Tip #16
Written by Vice Commodore Bill Whitney

During the last several months I’ve had the opportunity to witness a few vessel surveys and overhear the surveyor’s comments.
as they went through the major systems of the boats. It got me thinking about some of the things I’ve seen over the years but never
completely considered the ramifications of what I saw. One of these is the way we connect the thru-hulls and seacocks to the systems
inside the boat. Maybe its self-preservation or just that I’m a cheap Yankee but I don’t like holes in my boat. They let the water outside
become water inside unless you spend a lot of money putting the right stuff in the holes. Thru-hulls, seacocks, nipples, hoses, packing
glands, dripless seals and in some cases rudder seals are the more common things you find plugging the holes in your boat. You could
also have the occasional wooden plug or bung, but hopefully not many of them.

The principle concerns voiced during many surveys center around basic safety (as it should), mixed metals, and poor design
layout of many of these thru-hull and seacock installations. I was surprised to discover a few problems with my own boat over the
years but these were minor and I suspect added during “upgrades” to the boat. And I have to admit, some of them were installed by me.

As I was preparing this article my Jan.2012 issue of WoodenBoat magazine arrived in the mail and I was glad to see the piece
that Steve D’ Antonio did on seacocks and thru-hulls. It is a very good read and on a subject that everyone with a boat should review.
The essence of the article is that, just because the seacocks or thru-hulls are already installed in your boat it may not be done
“correctly” or with the right materials. I put “correctly” in quotes because there are no steadfast rules
governing recreational craft as there are with government mil-spec or commercial craft. The ABYC
(American Boat and Yacht Council) has widely accepted standards for pleasure craft, but there are
no “boat police” to enforce these standards. And many of our boats were built well before the
ABYC, or their standards, even existed! So while the boat is laid up, and as you go thru her greasing
the seacocks, it may be prudent to look over their installation and see if anything needs to be done to ‘
avoid letting the water outside from becoming the water inside. ‘

The ABYC standards recommend seacocks, such as the one pictured on the right, on any
fitting penetrating the hull that may be submerged when the vessel is heeled under maximum design
load. Since our Friendships sail with the rail at or under water on a stiff beam reach, it follows that
nearly all the thru-hulls should have seacocks. Guess what! My cockpit drains, which are submerged
even at the mooring, had no valves until I installed them about 15 years ago. From what I’ve seen on
other Dictator and Pemaquid glass hulls Ill bet there are more thru-hulls out there with no seacocks.

A sampling of some of these “less than ideal” installations occurred last year when a
recently purchased Pemaquid came to the yard and the new owner started going through the boat,
correcting these problems. On his boat there were no seacocks fitted on the cockpit scupper thru-
hulls; instead gate valves were used, the kind with the round blue handles you see on household
garden hoses. Inasmuch as the thru-hull mushroom has straight threads as shown in the picture, and
the gate valve has tapered pipe threads, there was only about 2 turns of thread holding back the
ocean. Gate valves, of course are a no go for boats as you cannot see if it is open or closed and it
could get stuck open with something blocking the gate closure.

The bilge pump was attached to the port cockpit scupper thru-hull with some brass nipples
and bronze street fittings. There was no vented loop (or any loop for that matter) in the bilge hose —

it ran straight downhill to the bilge. The only thing keeping the
submerged scupper thru-hull from siphoning the ocean in was the
backflow preventer at the pump. A piece of dirt, hair, lint or the run-away lime pulp from your last gin
fi and tonic stuck in the valve of the backflow preventer could result in a sinking.
we Another common problem is the seacock-to-hose connection. On the Pemaquid there was a
¥ complete lack of “pipe to hose connectors”, i.e. a fitting with a male threaded end and a hose barb end.
Instead every hose seemed to be fastened to the threaded end of a pipe with a single hose clamp, which
was all that the limited surface area allowed. In some cases the threaded pipe was not bronze pipe, but
brass. In many cases the pipe is not threaded where the hose is attached which doesn’t give the hose
much of a surface to grip.
Although not in the same safety category as a thru-hull, I ran into this same problem with my raw
water pump. The input and output connections were smooth pipe. Thankfully they were long enough
to position two hose clamps on the hose over the solid surface of the pipe to get a good seal. But it would not have taken much back-
pressure to blow the hose off the smooth pipe. There was also a mix of metals; stainless on one end and bronze on the other. Not a
show stopper, but I would rather see bronze hose barb fittings on both ends. Hose barbs are superior to threaded fittings because the
threads cut the interior surface of the hose, especially when compressed by a clamp.
On the Pemaquid, the cockpit scupper drains in the aft end of the cockpit on both sides had street connection fittings fiber

glassed into the sole, and the threaded end was used for the hose
connection. The reinforcement wires in the hose were rusted
from the bronze threads cutting into the hose. A simple twist of
the hose resulted in the hose just tearing away. The other end, at
the gate valves, also had the hoses connected to male pipe
threads.

As with most boats, these fittings are buried deep in the
aft lockers or under floorboards and are not very accessible,
either for inspection or for servicing. In this case, the bilge pump
hose was connected to a male pipe thread at the port cockpit
scupper thru-hull under the quarter berth. You have to ask
yourself: “How accessible are these valves if something happens
and they need to be closed?” Does your storage plan allow you
to get to all your valves? Do you have tapered wooden plugs to
drive into a broken thru-hull or fitting that fails?

The engine cooling water seacock had a street fitting on
it and the Groco seawater strainer had a brass nipple inserted
with the result of having two male threaded ends to which the
hose was connected. The raw water hose at the exhaust elbow
was the wrong type of hose. Someone had installed soft, unrein-
forced, rubber automotive hose that was kinked because it could
not sustain the bend required. A 90 degree pipe to hose connec-
tor would provide a better hose path.

The fuel filling hose was attached to a male threaded
fitting at the tank with the result that the seal was not tight,
allowing fuel to leak out of the hose/thread joint.

Another common problem, as pointed out in the
WoodenBoat article, is the stress that can be put on the seacocks
and thru-hulls by any tight radius hose bends or heavy pipe that
are attached to them. Ideally you should only use seacocks. They
have wide bases that support the mass of the valve and distribute
the load imposed by hoses. Thru-hulls with separate valves
attached to them have to rely on the mushroom head and backing
nut to support the side load imposed by hoses or other pipe
fittings attached to them. Either can be used, but carefully assess
the installation to see if any excessive side loads will be present.

Care also has to be taken when storing gear and equip-
ment to prevent damage to your seacocks and thru-hulls. A 30
pound anchor sliding across the stern locker can do a lot of
damage! Plan your storage and secure any heavy loads so they
can’t move around in a heavy sea.

Hamilton Marine and Jamestown Distributors have a
good stock of these seacocks and barbed tail pieces. So if you
find that your installation leaves something to be desired, now
might be the best time to upgrade.

Note: Special thanks to Bill Lundquist for providing
input to this article.