Ask Sail:To Bond or Not To Bond

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Q: I have a new-to-me Gulfstar 41 Ketch and would like some advice on bonding the through-hull valves. They are not bonded to anything or each other now. I have found a lot of conflicting and confusing information on the internet and wanted a professional opinion. If I should bond, then do they all get tied together? Only some? Do I ground them to my engine or negative bus bar? Thank you for any information you can give. Also, three of my ball valves are frozen, and I am not too keen on wrenching too hard on them. Is there a “trick,” or should I wait for my haulout next summer?

— John Laskowsky, Hudson, FL

DON CASEY REPLIES

You are right, the advice on through-hull bonding is both confusing and conflicting. For example, the ABYC standard recommends tying together all underwater metals electrically for corrosion control. However, if underwater components are not galvanically identical, bonding them completes the circuit and causes corrosion, which will need to be mitigated with sacrificial anodes. Bonding can protect underwater fittings from damage caused by onboard stray currents, but it has the opposite effect for stray currents in the water, inviting damage. It is easy enough to avoid onboard stray currents with good wiring practices, but you have no control over stray currents in the water, and with “hot” marinas today this is the rule rather than the exception. My best advice on this subject is that underwater metal components that are or can be otherwise electrically isolated should not be bonded.

As for your second question, too much muscle on a frozen valve can convert a potential emergency into an immediate one. If the design of your valves does not allow loosening to free them, you might try soaking them in a penetrant such as PB Blaster for a few days, then try again. Otherwise, the lesser of evils is likely to be risking not needing to close these valves until your next haulout. Once you have the valves working again, cultivate a habit of exercising them frequently.

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