Mailport August 2018 Issue

Beneteau Responds to Seacock Query

Beneteau wrote a detailed response to our recent query from a reader regarding seacocks in his Beneteau (“Seacock, Through-hull Caution” Mailport, PS July 2017). We are continuing to look at seacocks and seacock materials. The last Practical Sailor in-depth report on seacocks was in 1994, so this is long overdue. If you have a relevant seacock story to share, send it to the editor at

Here is Beneteau’s statement.

“As they are distributed throughout the world, all Beneteaus are built to the stringent standards of CE certification. CE is the most widely recognized official global standard, and one that is mandated as legally necessary by dozens of countries. The CE directives and legal requirements are used as the reference for the materials and systems needed in order to build Beneteaus.

“CE carries the weight of law in many jurisdictions, and Beneteau observes these; along with the legal requirements of governing bodies such as the US Coast Guard for the North American markets.

“For well over a decade, Beneteau has been installing through-hulls and valves made of a duplex brass alloy which is approved for use in sea water, and which are sourced through a respected supplier.

“Prompted by interest from a BoatUS member, Beneteau recently sent samples of the through-hulls and valves to be tested to confirm that they exceed the specific CE requirements of ISO 6957, the rule governing such items for corrosion issues. The testing was performed by the independent scientific laboratory of CETIM, and the positive results prove the examples met the ISO standard.

“As with many materials submerged in seawater, over years brass alloys may deteriorate due to chemical or electrical reaction (electrolysis), sometimes at an advanced rate due to external forces. Electrolysis may also be caused by stray current coming from the boat’s electrical system or from shore side sources (such as docks or surrounding boats).

“Electrolysis may also be the product of dissimilar materials in the water that create an electrical current that results in corrosion (batteries, metal bulkheads, etc).

“To our knowledge based upon over a hundred thousand boats produced, serious corrosion on through-hulls is episodic, and in our experience the incidence of failure is very, very rare. And those limited episodes can normally be traced to some key contributor; such as stray current, improper wiring, failure to inspect on an annual basis, lack of maintenance, etc.

“Beneteau confirms that it is mandatory to have a competent professional perform a thorough annual inspection of all underwater appendages, items and surfaces for function, integrity or performance, and that includes through- hulls and valves. The inspection of the through-hulls should be undertaken from both the inside and the outside of the hull looking for any color change.

“We also require that there must be regular replacement of the protective zincs anodes (or magnesium if in fresh water). In the case of rapid deterioration of anodes, the cause of such activity must be investigated and a fix for stray current or the exceptional presence of dissimilar metals must be addressed. In some extreme cases it is not uncommon to have anodes erode within a matter of a few weeks. Those examples require extra anode protection or more serious remedies, and expert professionals should be consulted in such instances.

"In some cases it may be necessary to replace through-hulls after years of use, which in those occurrences are considered by Beneteau to be normal maintenance. There are also examples of through-hulls which, due to standing condensation or a leaking connection, visually appear to be severely degraded on the surface, only to find that after a short minute or so of polishing they are fully structurally sound, functional, and visibly improved. With proper maintenance and vigilance, through-hulls and valves will remain reliable and secure.

"As a general reminder, it is recommended that boaters close all through-hulls upon leaving any unattended vessel."

Wayne Burdick

President, Beneteau Inc.

Comments (24)

I owned a 1987 Catalina 30, Mark II. It had four gate valves instead of seacocks. I had them replaced with Forespar Marelon seacocks. Over the next six years that I owned the boat, two handles sheared off while opening or closing them. I lubricated them every year during winter layup. I exercised them regularly during the season. Forespar replaced the handles at no charge but I am not a fan of their seacocks.

The boat was always sailed in fresh water, Lake Erie.

I currently own a 1998 Beneteau Oceanis 321 and am the captain of a 2013 Beneteau Oceanis 50. I lube the seacocks every winter. Both boats have always sailed in fresh water, Lake Erie. Zero problems with the seacocks.

Posted by: mark2 | August 7, 2018 10:36 AM    Report this comment

Beneteau may be the #1 boat builder in terms of quantity, but not quality.

Brass has no business being in any seacocks. House plumbing use of brass valves is OK as a house doesn't normally sink. The EU/CE standards for seacocks allow the use of brass, but the rule states that seacocks must be changed every five years.

Greasing seacocks should be part of a maintenance program, but replacing them shouldn't have to be. Wilcox-Crittenden, Blake, Spartan, Groco make or used to make all bronze seacocks and mine are over 40 years old and in perfect condition.

Bronze seacocks last decades, but are more expensive. Buy cheap tools and you buy them twice.

Posted by: George DuBose | August 7, 2018 6:55 AM    Report this comment

We have a 1986 C&C33 Mark 2 with Marlon thru hulls we have owned the boat since new and no thru hull problems. I was there when C&C was deciding whether to move to Marlon or not, obviously the correct. Malaika our C&C33 has lived in saltwater for 32 years with no problems. Regards Brian

Posted by: Brian Angus | August 6, 2018 1:46 AM    Report this comment

Related question from a very old salt. Is there any significance to the labels "manganese bronze" or "silicone bronze". Because of info from many years ago, I have always required silicone bronze, and never been disappointed, but then maybe I would have been as happy with manganese bronze, had I used it. From discussions with others, the Marlon valves are excellent, their handles are not.

Over the years, I have not had to replace any thru hull valve for deterioration of the valve (replaced several for other reasons). I have replaced all, several times with most, the thru hull mushroom itself, and have had varying results. Main thing is to look for discoloration, a red-ening of any copper based submerged item, and replace it.
I have owned "Someday" since 1983, and sailed her extensively; been cruising off and on since 1996, lived on her since 1992.

Posted by: Umpqua Chief | August 5, 2018 1:17 AM    Report this comment

FYI: A pdf of a fairly detailed overview of the seacock material issue authored by Surveyor Paul Stevens and published in the June 2011 issue of Yachting Monthly can be found by searching: The four main types of seacocks: pros and cons

Posted by: CA Dude | July 31, 2018 2:31 PM    Report this comment

I own a 2010 Beneteau 50, my first USA Beneteau and previous B was French built a 45f5. As some of you poo poo Beneteau, they are the #1 builder in world for a reason. My 45f5 had thru hulls and valves replaced by her new owner after 22 years! My 2010 Beneteau in brackish Baltimore, MD just got 11 thru hulls and 11 ball valves from Groco. I also spent the money to bond every valve to the entire boat. Unfortunately I didn't have the time to do the project myself but the $8000 spent makes for easy sleeping at night.

Posted by: | July 30, 2018 3:28 PM    Report this comment

I have a 2003 Jeaneau 43 DS, which has these valves. I don't have any leaks or problems with them but I would like to replace them with composite valves. Unfortunately, I don't know whether they delivered my boat (to the US) with thru-hulls that use BSP threads, or NPS threads. I had one valve - a 2" holding tank valve, replaced when the boat was in France, and the French used a BSP valve, without changing the thru-hull. They also gave me a second valve for the other holding tank, and it also has BSP threads. However, the valve that was originally installed on the boat appears to have NPS threads, and all the valves I can find in the US have NPS threads (the straight ones, not tapered).

Does anyone know whether these boats use BSP threads, or NPS threads? I want to replace the metal valves with Trudesign valves, but have to know the threads before I order them.

Posted by: rxc | July 29, 2018 1:52 PM    Report this comment

Wow, I'm very impressed with the knowledge of the Practical Sailor readership.

Posted by: Guffin Bay Sailor | July 29, 2018 8:07 AM    Report this comment

Wow, maybe it would have better if Beneteau did not respond at all, however they did and the response is pretty clear that their understanding of the subject, corrosion, is way below par. The term "Electrolysis" is used three times, all improperly, therefore one has to doubt their explanations or to put it simply - they don't know what they're talking about !
BTW, I wonder if the author, Wayne Burdick President, Beneteau Inc., ran this by his engineers ?

Posted by: Capt. Singood | July 29, 2018 4:42 AM    Report this comment

Wow, maybe it would have better if Beneteau did not respond at all, however they did and the response is pretty clear that their understanding of the subject, corrosion, is way below par. The term "Electrolysis" is used three times, all improperly, therefore one has to doubt their explanations or to put it simply - they don't know what they're talking about !
BTW, I wonder if the author, Wayne Burdick President, Beneteau Inc., ran this by his engineers ?

Posted by: Capt. Singood | July 29, 2018 4:40 AM    Report this comment

Many years ago, as a draughtsman working on naval vessels an alloy was used on warships called CuNiFe, an alloy of copper Nickel and Iron. I wondered whether there was any recent experience of this material.

Posted by: Pramsec | July 28, 2018 9:40 PM    Report this comment


Knucklehead Beneteau doesn't know the difference between GALVANIC CORROSION and ELECTROLYSIS.

Galvanic Corrosion
Occurs between dissimilar metals (metal loss) based on their position on the galvanic scale (anode vs cathode.) It can be caused by metals in direct contact (e.g., a stainless rivet in an aluminum mast) or by stray current (e.g., your prop being eaten up by a dockmate's poor electrical setup.)

Is, for example, splitting an electrolyte into components (like water into H, O2) when passing a current thru it (as in charging a wet cell battery.) Or your grandmother removing unwanted hair using a depilatory machine!!

Posted by: KMan | July 28, 2018 4:20 PM    Report this comment

My PJ Nautor Swan 43, built in 1970, has BRONZE Blakes Seacocks. The boat has been in salt or brackish water since then with a total of a few years on the hard. The seacocks are in perfect condition with a bit of a greenish tarnish.

Blakes offers the exact same seacock for sale today. When you design and build it right, you don't have to think about it again. Granted, they are not cheap. I do not want to have to think about seacocks when I am offshore in a blow or when I leave the boat in a distant marina for months at a time.

It is pretty simple, isn't it? Holes in the bottom of the boat are the most likely thing to cause it to sink. Why would anyone skimp on a seacock?

Posted by: TrustyNereus | July 28, 2018 12:51 PM    Report this comment

I realize that bronze/brass fittings have been used in ship construction, probably since the bronze age, but why are we still using it if we know that it has this issue in a salt water environment?

Our last two boats have Marelon fixtures and I don't have to worry about any stray electricity effect them. Do I have other things that I need to worry about, or am I missing something here? Is the boating industry just to slow to adapt to newer technology?

Posted by: FKoehlmann | July 28, 2018 12:05 PM    Report this comment

I keep seeing references to "DZR" brass. No, No, NO!

We need to put this to bed.

DZR brass is not any more resistant to stray-current (electrolysis) corrosion or galvanic corrosion than any other brass.

Reading here:


"However, if DZR brass components are fitted in contact with parts made from different
alloys or metals, an electrolytic cell might be formed, with the resulting risk of galvanic
corrosion. The anti-dezincificant properties of DZR brass give no effective protection
against galvanic corrosion.

The conditions that trigger galvanic corrosion are:

1. An electrolyte bridging the two metals, which may not necessarily be aggressive to
the individual metals when they are not coupled;
2. Electrical connection (direct contact) between the metals;
3. A significant difference in potential between the two metals to provide a significant
galvanic current;
4. A sustained cathodic reaction on the more noble of the two metals, in most practical
situations the consumption of dissolved oxygen in the electrolyte.

Sea water is a very effective electrolyte and undoubtedly the most widely studied. Many
experimental studies have led to the definition of the galvanic series of metals in sea
water, where metals and alloys are classified according to their potential. The general
recommendation is that a coupling of two metals with very different potentials bridged by sea water should be avoided because the more electronegative metal acts as an anode and is quickly corroded; the obvious exception is the purposeful use of zinc or aluminium sacrificial anodes."

Posted by: Electronaut | July 28, 2018 11:38 AM    Report this comment

I think Beneteau has answered the question. They used a Brass alloy with a high level of zinc. It squeaked past the CE standard and that's what Beneteau cares about. Boat owners be damned. So Beneteau saved $10-$20 per through hull.
They just tarnished their own reputation.
I you own a Beneteau in salt water you had better be inspecting your through hulls and planning for their replacement with a better materials.

>>As a general reminder, it is recommended that boaters close all through-hulls upon >>leaving any unattended vessel.

What is he thinking? If a sea cock fails and breaks free of the hull, closing your seacocks will not prevent your boat from sinking. The boat is still going down unless you think quick and have some way to plug the hole left in the hull from the failed sea cock, assuming you can get to it quickly.

Posted by: Dave9111 | July 28, 2018 11:34 AM    Report this comment

The duplex brass that Beneteau refers to is commonly called DZR Brass, dezincification resistant brass. It is approved by the CE standard but not by US standards.

It has a much higher zinc content than the 85-5-5-5 bronze typical of US made thru-hulls and seacocks. DZR Brass is subject to dezincification, just not as fast as yellow brass.

If I recall correctly, DZR Brass is about 20 to 25% zinc. The bronze US manufactures use is only about 5% zinc.

I wouldn't trust DZR Brass to last much more than five years in salt water.

Beneteau uses the cheapest hardware that meets CE standards, not the best available.

Posted by: HopCar | July 28, 2018 10:34 AM    Report this comment

To the best of my knowledge (having researched this over 20+ years), there are NO alloys of copper, including the highest quality bronzes, that are not susceptible to one degree or another to corrosion from electrolysis due to impressed current.

If there is enough stray current flowing through ANY kind of bronze, one or more of the alloying metals is going to be dissolved over time. Often it is the zinc that is depeleted first, but after the zinc is gone, the next metal up or down in the series will be dissolved next. What is left is the 'sponge-like' remnants of the original alloy.

The problem is stray current.

Better alloys of Bronze (specified in the applicable standards, as Beneteau states) will dissolve more slowly, but if you have a stray current problem even these are going to fail after long exposure to electrolysis.

Too many boat owners ignore stray current. Only a small fraction (less than 10%) of my clients even know what a hull potential survey is.

For my part I have seen many failed thru-hulls. All of them were caused by stray current.

Beneteau's response is thorough and accurate.

Posted by: Electronaut | July 28, 2018 10:27 AM    Report this comment

I don't think it matters which alloy of brass is in Beneteau's sea cocks. The bottom line is that brass exposed to sea water is subject to "dezincification". The zinc part of the alloy dissolves just like our zinc sacrificial anodes, invisibly weakening the structure of anything made of brass below the waterline (and even above). Failure of brass fittings on boats in a salt water environment is inevitable. Bronze is the best metal alloy below the waterline, being a mixture of copper and tin, which is more "noble" (less reactive) than zinc. Beneteau prices its products for wide market accessibility, probably with the assumption that their brass fixtures will be replaced before they fail. Maybe.

Posted by: rersk | July 28, 2018 10:27 AM    Report this comment

Is duplex-brass a cost saving for Beneteau? Seems so as bronze or plastic would be better choices.

Beneteau covers their bases by advising closing all seacocks while unattended. Fine for a small boat but how many owners of 40 footers with a dozen or so in inaccessible places actually close them.
Instead they rely on the integrity of their seacocks.

Posted by: Ronbo | July 28, 2018 10:16 AM    Report this comment

The referenced ISO standard discusses using ammonia atmosphere to search for indicators of stress corrosion. While easy to perform, it is not clear how such a test relates to the failure of fittings on boats immersed in salt water.
The failure mode of brass fittings is usually dezincification, that is, leaching of the zinc component of the alloy into the surrounding water. It is accelerated by stray currents, rapid water flow, and the other risk factors cited by BEneteau, but it exists even in their absence. THe use of bronzes reduces the rate of zinc leaching, and resists the corrosion of the metal by any of the factors cited. Using bronze cannot prevent all corrosion, but it can reduce the rate to an acceptable level.

Posted by: David_L | July 28, 2018 10:02 AM    Report this comment

Beneteau's response is what one would expect from the world's largest sailboat builder.
High school chemistry is not their strong point. Surveyors rarely find good quality bronze seacocks failing. Unlike Beneteau's so called "bronze seacocks". Beneteaus' statements about "standards" reflect the failure of the boating industry's reluctance to upgrade standards. Anyone comparing electric, plumbing and mechanical installations between recreational craft with those of USCG (or similar) and commercial marine standards will be quite astonished at the differences. Commercial builders jealously guard their reputations by building to top standards to maintain their reputation for "getting the job done at sea". Recreational builders focus on style.

There's no doubt Beneteau makes some fine sailing boats. But their mechanical, electrical and plumbing installations are far below what we've come to expect from America's best builders. It's not unreasonable to expect those systems to function properly for a decade or two after being put into service. Without having to be redone. Seacocks are just the most visible aspect of cost cutting to keep prices low. Owners subsequent pay for the refit costs.

It's a good education to inspect the engine rooms of decades old commercial and offshore fishing craft, look around and ask what's been replaced. Odds are most of the gear is original for the simple reason that the builders and marine standards association have one goal - to bring the ship/boat home safely.

Peter I Berman
Norwalk, CT
Author: "Outfitting the Offshore Sailing Boat"

Posted by: Piberman | July 28, 2018 9:28 AM    Report this comment

Check out the Wikipedia entry for 'Brass'. Down in the text , in a table is stated:

"Alpha-beta brasses 55-65 (% copper) 35-45 (% zinc) Also called duplex brasses, these are suited for hot working. They contain both α and β' phases; the β'-phase is body-centered cubic and is harder and stronger than α. Alpha-beta brasses are usually worked hot. The higher proportion of zinc means these brasses are brighter than alpha brasses."

Doesn't sound like a good material to me due the proportion of zinc.

Posted by: gkjtexoma | July 26, 2018 6:33 PM    Report this comment

what exactly is a duplex brass alloy ?
the terms brass and bronze are to loose to use if you want to know the metallurgy.
They are all referred to as 'copper alloys' since copper is the base metal.

The metal should have an alloy number. that is the only real way of knowing what it contains.

Posted by: sailing Jack | July 17, 2018 4:47 PM    Report this comment

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