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Solved problems · Plumbing · Crew answer

What should I do about a seacock that won't turn?

A seized seacock is a flooding risk because you can't close it in an emergency. Try gentle methods only. If it won't move, plan a haul-out instead of forcing it.

Symptom

A seacock handle won't move, or only moves partway, during routine checks or when you need to close it.

Likely cause

Seacocks that aren't worked regularly seize from marine growth, salt crystals and corrosion inside the valve. Old gate valves and corroded bronze can seize permanently. Ball valves can stick when the seals dry or grow tight.

Stop now if

The seacock or its through-hull is leaking, cracked, wobbles, or shows pink or crumbly bronze. Don't apply force. Keep the bilge pump ready, have a correctly sized soft wood plug at hand, and arrange a haul-out. Never put a long cheater bar on the handle.

The fix, in short

  1. Get ready first. Tie a soft wood plug sized for the through-hull next to the valve, and make sure the bilge pump works before you try anything.

  2. Use penetrating oil and patience. Apply penetrating oil around the handle stem and let it soak. Then rock the handle gently back and forth in small movements.

  3. Use only modest leverage. A short wrench on the handle is the limit. Too much force can snap the handle or the stem, or crack the through-hull, and then you can't close it at all.

  4. If it moves, work it fully. Once it frees, cycle it open and closed several times. Practical Sailor advises checking every seacock for smooth operation and servicing any that are stiff or frozen.

  5. If it won't move, plan a haul-out. Leave it alone and have the valve serviced or replaced out of the water. Never take a seacock apart while afloat. Meanwhile, check the hose and clamps. Practical Sailor recommends double stainless clamps where the hose barb allows. Keep the plug tied at the valve.

  6. Prevent it. Open and close every seacock regularly. At each haul-out, service and grease them as the maker recommends. If the boat has a bonding system, check that the bonding wires and connections are clean, tight and free of corrosion. Keep a soft wood plug tied at every through-hull.

Written by Sailor Cruiser crew. General guidance, not an inspection of your boat.

Equipment involved

  • Through-hulls: Seacocks (ball valves or tapered plug valves), through-hull fittings, hoses and clamps

Related guides

Sources

Background reading we checked while writing this answer. The wording above is our own.

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