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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance
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  #1  
Old 04-12-2011
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Bronze seacock/stainless handle=grounding?

I'm about to launch into one of the few projects I've yet to do on my Gulf 32 and have come across a question I didn't anticipate. While buying all the hardware today I read about one of the seacocks that they recommended grounding it because it is bronze and has a stainless handle. I've always read that grounding thruhulls and seacocks is unecessary and in fact problematic. I've searched here and on cruisers and read every word in Casey, Calder, and the fabulous Mainesail descriptions, but haven't seen this addressed. I must be missing something.

The last thing I want to do is to run wire to all my thru hulls! Anyone knowledgeable about this, I would sure appreciate some two cents.
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Old 04-12-2011
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What brand of seacock is this? Is it a marine grade valve? Usually there is an insulator on the stem and a rubber seal on the ball of the valve that isolate the ball, stem and handle from the bronze valve body. If you buy non-marine grade valves they don't have this and the ball and valve body corrode via galvanic activity (grounding the valve body won't help either). The electric potential exists between the dis-similar metals; and grounding valve bodies to prevent corrosion might actually increase galvanic action not reduce it.
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Old 04-13-2011
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The seacock is a Marine Hardware unit that is UL Listed Marine and all that. Funny thing is, most of my purchases were Groco valves, but they were out of the 1" model and so I bought this Marine Hardware unit. The Groco valves say nothing about needing grounding.

You are right, keelhaulin, and the Marine Hardware unit says the following:
• Housing cast of heavy-duty 85-5-5-5 naval bronze; machined with tapered pipe threads (NPT)
• Chromed bronze ball for maximum saltwater corrosion resistance; SS ball stem
• Grounding screw for connection to the boat's bonding system, (sizes 1/2" to 4")
• Drain plug for easy winterizing (sizes 3/4" to 4")
• Handles are coated with a thick, non-slip plastic for a sure grip
• Bronze body⁄SS hardware - cathodic protection is required; includes grounding screw for connection to the boat's bonding system

I have a call into Marine Hardware to find out their viewpoint. Maybe it is that this unit is not insulated from electrolysis properly and thus the warning, but in that case, why is rated for marine use?
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Old 04-13-2011
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Just off the phone with an informative Groco guy who explained that Groco expects all their ball valves to be bonded, even though they don't specify that in their literature and realize it creates its own problems. He explained it really has nothing to do with the stainless/bronze combination, as the stainless is high grade and doesn't have much reactivity with the bronze. The concern is just for the bronze itself, thru hulls included. He admits this is the corporate line for warranty claims, but that bonding is not a black and white issue.

It seems from this that given that my bronze thru hulls have never shown any particular electrolysis problems (though I am likely to replace them anyway since they are 20 years old((unless when I pull them they are really bomber)))that I am safe in assuming that not bonding is not much of an issue and perhaps less an issue than tying everything together.

Interesting stuff...
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Old 04-13-2011
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I'd say do not ground them. Here's a link to a good treatise by Stan Honey on the subject reprinted from Practical Sailor.
Grounding
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Old 04-13-2011
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Thanks Mitiempo, nice article. Seems everything is coming clear and this has been nicely educational. The article you linked to confirms what others have said that bonding is not preferred and can cause other problems. So long as one is using high quality and proper marine products then the isolated systems are at less risk than if combined.

The manufacturers recommend bonding from a cya perspective because failure of one of their valves during their one year warranty period would require some massive electrolysis issues that could only be caused by significant external currents. In which case, and with a top notch bonding system, you might avoid damage to the valve, which is their position.

I will not be bonding my new thru hulls and appreciate the input here to help me think this through.
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Old 04-17-2011
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Quote:
Originally Posted by bwindrope View Post
• Bronze body⁄SS hardware - cathodic protection is required; includes grounding screw for connection to the boat's bonding system.
What this means is that IF you choose to use stainless bolts to mount the flange of the seacock to your hull; you should ground the bronze fitting. Personally I think I would use Silicon Bronze mounting screws/nuts and forget about bonding the seacocks.
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Old 04-17-2011
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Agree

The stainless handle is not an issue as it is not exposed to the water.
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