Various pieces of equipment use salt water or raw water to function. Marine heads typically use sea water to flush. Galley sinks can use sea water to help rinse dishes. The engine uses sea water to keep it within proper operating temperatures. Even refrigeration can use sea water to dissipate heat. The key issue is to control the flow of that sea water: to let it in and out when it is needed, and keep it out when not.
A hole below the waterline in a boat can emit a tremendous amount of water into the boat. The displacement of the boat forces the boat down in the water column while an open hole under water allows the displaced water to go through that hole at a furious rate. So, it is important to be able to close off that hole when the water is not needed.
OK, the controlling mechanisms are seacocks. Seacocks are valves that when connected to threaded through-hull fittings create a solid unit for either letting sea water in and out, and, as important, keeping sea water out. Without getting too technical, appropriate seacocks are designed with either tapered plugs or ball valves.
Both work quite well and each has their share of proponents.
When Harmony was constructed, she had bronze tapered plug seacocks installed. There were at least 7 seacocks or holes below the water line: 2 cockpit drains, 2 holes for the forward head, 1 for the forward head sink, 1 for the engine, and 1 for the aft head. In some cases a sea cock had multiple items plumbed into it, and this presented some safety concerns. Moreover, after years of neglect, these tapered plug seacocks had become either frozen open or closed.
In order to ensure the integrity and safety of the raw water system on Harmony, we decided to replace all seacocks with new bronze ball valve seacocks. We also chose to eliminate unnecessary through-hulls and simplify the overall plumbing. We chose Groco seacocks and through-hulls because of their quality and because they feature stainless steel balls rather than chromed brass ball valves.
Since we had chosen to use composting heads, we could eliminate at least 3 through-hull fittings. GREAT! Than meant we only had one seacock, the forward head sink, outside of the engine room. This would narrow the search for leaks if a through-hull connection ever failed. We could clean-up the myriad of connections on each through-hull and increase the system's integrity.
Removal promised to be quite a chore since the existing through-hull fittings and seacocks could not be easily disassembled: you know big wrench turned by huge biceps, which I lack! Not to mention the fact that whatever had been used to bed the fittings took its job very seriously! So, I simple took a Dremel tool and cut quadrants through the external mushroom head of the through-hull and, because the bronze was malleable, I pried the mushroom head off. After that the seacock and threaded piece of the through-hull spun easily out.
The new seacocks were installed on backing blocks I had cut from 1/2 inch solid fiberglass. This added an extra amount of strength to the assembly. These seacock were through bolted and the through-hull screwed into the seacock. Once I started the process and refined my technique, I was able to remove and install all of the fittings with about 2 full days of effort.
I bedded the through-hulls in 3M 4200 so that I can remove them later if necessary. I replaced all existing hoses with new and appropriate hoses. All that is left to do is to attach an appropriate sized plug to each seacock to use in case of failure.
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| Harmony's Engine Room Port Side Seacocks - clockwise from bottom of picture - 3/4" water maker supply, 1 1/2" cockpit drain, 1 1/2" engine raw water |
Beth and I will be able to sleep soundly knowing that all through-hulls are robust and secure. I am sure the insurance company will be happy, too!
Fair Winds and Following Seas!
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