Seacock Inspections

Just because seacocks are out of sight doesn't mean they should be out of mind.

Like any equipment located out of sight in the dim recesses of the bilge, seacocks generally receive little thought or attention — unless they fail. Knowing some inspection and maintenance tips can help an owner keep the boat’s seacocks ready, willing and able.

The most common seacock types are tapered plug, expanded rubber plug and ball valves. Gate valves are notorious troublemakers and are not recommended for use as seacocks. Not only are the worm gear and the associated guts of the thing prone to corrosion and failure, it’s possible that trash could prevent the gate from closing properly. An un-flanged ball valve screwed directly onto a through-hull is also fairly common, although this isn’t really an acceptable practice. Modern ball-valve types that feature a supportive flange, like the traditional tapered-plug units, are a much better option.

Material-wise, seacocks will be made of either marine-grade bronze or composite construction (e.g., Marelon).

1 / Seacocks should be inspected at least monthly, both to ensure proper operation and to head off any potential problems. Start with a visual inspection of each seacock, keeping watch for issues such as leaks, broken hose clamps, damaged or missing components (e.g., handles), and corrosion. If it’s part of a bonding system, check to make sure all the connections are tight and corrosion free, for proper operation.

2 / Verify the installation of backing blocks and that each is stable, leak free, properly sized (i.e., the surface area is greater than that of the seacock flange) and in the case of wood, rot free.

3 / Check the seacock for smoothness of operation, ensuring it not only opens and closes but can be easily reached in an emergency and that the handle can be moved through its full range of operation without being blocked by anything, including equipment and cabinetry. Seacocks that are frozen or otherwise inoperative should be serviced immediately and returned to full operation.

4 / Other installation faux pas to watch out for include the use of PVC fittings or plastic-to-metal joints. Both materials have different expansion and contraction rates, which can result in plastic fitting cracks or splits. Also watch for installations that utilize a short piece of pipe or hose between the seacock and the through-hull, which introduces a potential failure point inside the hull that is unprotected by the valve.

5 / If there’s any question whether a seacock is working properly, remove the hose and look through the seacock to verify its operation or to spot blockages. If the vessel is hauled, another option is to shine a flashlight into the through-hull from the outside and observe its operation while someone inside opens and closes it.

6 / Next up, inspect all seacock hoses and make sure they are of the correct type (marine grade and approved for use on fittings below the waterline), free from damage and deterioration, and that each end is double clamped with stainless steel clamps, where there is sufficient hose barb to allow it. That last bit about sufficient hose barb is important — otherwise, the installation of a second clamp will crush or cut the hose. Finally, during the inspection keep in mind that all hoses have a limited lifespan. Recommended replacement time varies between manufacturers; however, 10 years is commonly quoted, regardless of appearance.

While specific maintenance requirements will vary based on the type of seacocks that are installed (e.g., plug, ball, bronze, Marelon), general maintenance should include operating the seacock monthly and a good greasing at least twice a year, even for so-called maintenance-free
units. Seacocks without a grease fitting can be lubricated while a boat is in the water by following these steps:

1 / Close the valve
2 / Pull the seacock hose
3 / Remove remaining water from the valve/tailpipe
4 / Swab a suitable waterproof grease onto the ball
5 / Inspect the hose for damage, deterioration, corroded hose clamps, etc., and then reattach
6 / Exercise the valve four or five times to spread the lubricant
Note: Steps 4 through 6 can be conducted from outside the hull when the boat is hauled, to lubricate the opposite side of the ball and seals.