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Old 06-30-2011, 11:12 AM   #1
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Bond above water thru-hulls?

All my thru-hulls were bondend....above and below the water line. That was from 1984.

My electrical books say NO the above water through hulls. Is that the 2011 consensus?

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Old 06-30-2011, 11:44 AM   #2
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RE: Bond above water thru-hulls?

I would think that bonding out-of-the-water thru-hulls is uneeded since the purpose of bonding is to bring immersed metals to the same galvanic potential.
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Old 06-30-2011, 01:40 PM   #3
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RE: Bond above water thru-hulls?

I completely agree with Jay's comment and will go one step further, with apologies for opening up another can of worms...

We are currently chasing down some electrolysis issues with our boat, which at the moment has all underwater metals connected. Although the expert opinions vary, the majority are saying to NOT bond these metals together. The thinking is that if you have a problem with a fitting, it stays isolated to that fitting rather than sharing the wealth.

I'm not an expert but am passing on the opinions expressed directly to me by experienced surveyors, shipwrights, and marine electrical folk.
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Old 06-30-2011, 03:36 PM   #4
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RE: Bond above water thru-hulls?

All connected together then to a large zinc?

How about seawater strainers? Connect them up too?
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Old 06-30-2011, 04:09 PM   #5
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RE: Bond above water thru-hulls?

I just installed two new through hulls/seacocks to replace two that were substandard. The old ones were not bonded and I have not yet bonded the new ones. I am undecided whether to tie the new ones into the bonding system. Should I?
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Old 06-30-2011, 07:36 PM   #6
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RE: Bond above water thru-hulls?

I replaced my 1976 through hull gate valves a few years back, I found no bonding.* The old valves were as solid as a rock, no sign of corrosion or electrolysis and still functioned perfectly. *I asked around the boat yard and heard pro's and con's both ways.*But those who should know, said you are better off keeping them electricly isolated from each other and not bond them together.**
Unfortuately, I'm not and electrical engineer and I found like many other subjects, everybodies got an opinion and they're not engineers either. *So I left them unbonded as the originals were and will check them on a regular basis for any signs of problems.
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Old 06-30-2011, 09:57 PM   #7
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RE: Bond above water thru-hulls?

Yes, I also have mixed feelings about this. Some of my fittings are bonded, some I suspect not, the impression is the ones I know are, corrode the most.
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Old 07-01-2011, 09:58 AM   #8
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RE: Bond above water thru-hulls?

The ones above water do not have to be bonded, but a lot also depends on your bonding method system.* If the ones above the water are already bonded, then the new ones might have to be if the wire is daisy chained from one to the next as you will break the chain.* So look at your bonding system first. *
*

Also you might want to re due the bonding system as it might not be working/conducting as it does not take much to stop the tiny flow.* So at least check and clean the bonding system as it is one of the most largest, important system on the boat and the least understood.

While our are on the hard, you may want to eliminated, take out and fill some of the through hulls, especially below the water line.* I took out all the though hulls below the water line except the two for the engines.* All the water is pump up and over above the water line, the toilet is fresh water.* If when I need a below the water through hull for something it will be ONE and with a manifold for multi needs.* When at the dock all the through hulls below the water are CLOSED, and I sleep better at night.
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Old 07-02-2011, 08:03 AM   #9
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RE: Bond above water thru-hulls?

Quote:
dwhatty wrote:
I just installed two new through hulls/seacocks to replace two that were substandard. The old ones were not bonded and I have not yet bonded the new ones. I am undecided whether to tie the new ones into the bonding system. Should I?
*If you did not see any galvanic corrosion on the ones you removed, it is unlikely you will need to bond the new ones.* On the boats I have owned, I have always had one or two un-bonded thru-hulls for various reasons, and with one exception, they remained un-bonded because there was no apparent corrosion occuring.

The one exception was a generator sea water supply thru-hull which had obvious corrosion, and bonding it solved the problem.

The*bonding of thru-hull fittings and strainers can be a rather mysterious process, and many boaters/builders seem to think that it is better to bond all immersed fittings than not.* But one of the boats I owned (for 24 years) was equipped with an Electroguard cathodic protection system, and it*actually worked better when two of the forward thru-hulls were disconnected from the bonding system.* This was a wood boat that was sensitive to over zincing.

A big part of the solution on bonding/corrosion issues*requires*regular inspection*of the fitting and bonding system connections.* In addition, it should be recognized that*many bonding system/zinc protection issues are boat/area/usage specific, and it may take a number of years to understand how your system is working.**
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Old 07-07-2011, 12:57 PM   #10
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RE: Bond above water thru-hulls?

Quote:
Jay N wrote:
*
A big part of the solution on bonding/corrosion issues*requires*regular inspection*of the fitting and bonding system connections.*

*That is how I see it.*A wire gets pinched or comes undone, there go's the bonding system.

Four basic conditions must be present for corrosion to occur.

1. There has to be a positive or anodic area. It is called the anode and posseses the lowest potential. It is the metal that will corode.

2 There has to be a negative or cathodic area. it is called the cathode and posses the highest potential.

3 There has to be a path for the current to flow. This is called electrolyte. This is the water

4 there has to be a curcit path for the current to flow. This is any interconnecting material. *A wire.

Most thru hulls are not connected to any other metal. Just a hose (not metal) unless you connect them*by *bonding*them. So why bond something and creat a path for corrosion.

SD
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