Jin and Cathy, I will echo Paul's comment. Brass is the worst possible thing you could use, due to the high zinc content.

If you put in brass seacocks, and they subsequently fail, you can expect your insurance company to find you at fault.

So-called "DZR" (de-zincification resistant) brass mentioned above does not provide any protection from stray-current electrolysis! It is merely a (slightly) better choice for non-critical applications. It should never be used for thru-hulls.

This, or similar, problem surfaced a few years ago when a writer queried a number of yacht surveyors and it emerged that numerous through-hull/seacock devices were found close to mechanical failure, or had failed. This was raised by the writer with the MDs of several UK yacht insurance brokers and a couple of the mags.... and it was investigated.

It emerged that many European boat builders had stopped fitting expensive marine bronze through-hulls, and instead started fitting much cheaper common brass units. Why?

It emerged that the EU Recreational Craft Directive was negotiated by civil servants with limited technical knowledge, relying mostly on the larger Euro-manufacturers ( i.e French ) to keep them straight. That led to a requirement which stipulated that such items should last 'a minimum of 5 years from being put into service', if my reading is correct. Of course, marine bronze was already known to last a lifetime, so this permitted the manufacturers to change to a far cheaper material, simple brass- without telling anyone.

They could have fitted Dezincification Resistant Brass, and still saved money, but didn't.
It's NOT enough simply to trust blindly in The Standard. One needs to read it, and reading the ISO 6957 Standard referenced by Beneteau seems to relate to Stress Corrosion, not dezincification.

Some boats sank. IMHO, lives were put at risk by this sharp practice. This problem is continuing.

We need some expert comment here and Practical Sailor, with its many technical editors, is ideally positioned to commission it.

I replaced all original thru-hulls, both metal and plastic, with brand new Marelon. The design of Marelon thru-hulls has been improved due to improving ABYC standards, so the new ones are stronger than the old. Easier to sleep!

"American bronze is kinda snobby and of no use" ...really? After scores of years being sold on Swedish or German steel now the objection to American as a standard smacks of a phoney cultural issue. "Kinda" like resistance to our superior industrial system copied by the rest of the world. Suggest you look up ASTM origins.

I think the term American Bronze is kinda snobby and of no use. Most countries can make any quality level of bronze you request. If you are going to reference a rust resistant impact resistant level of bronze you should use the proper names. Its like calling 316 stainless American stainless.

I think the term American Bronze is kinda snobby and of no use. Most countries can make any quality level of bronze you request. If you are going to reference a rust resistant impact resistant level of bronze you should use the proper names. Its like calling 316 stainless American stainless.

HopCar, would you please provide more information about DZR not being fit for underwater throughull, valves and fittings? All I have been reading is that DZR was close to be as good as Bronze for this application. Do you have scientific proof for this statement? Thanks

HopCar, would you please provide more information about DZR not being fit for underwater throughull, valves and fittings? All I have been reading is that DZR was close to be as good as Bronze for this application. Do you have scientific proof for this statement? Thanks

Any surveyor worth his mettle ought be able to identify whether the seacocks are standard US bronze issue. Or something else. Generally US boatbuilders of voyaging sailaboats and larger powerboats use conventional US bronze seacocks and other critical equipment such as steering quadrants. The problems come evaluating foreign built boats claiming "bronze seacocks". High school chemistry students often learn the difference between bronze and brass. And why real bronze (ASME specs) can last virtually forever under water.

We recently looked at a 1998 Beneteau 46 Oceanus. Every single underwater thru-hull seacock shows signs of incident failure. And need to be replaced. It's a major job. They all looked like brass. Moreover the Beneteaus usually do not employ heavy backup plates.
Relying on the hull thickness to provide support.

In the "old days" it was not uncommon for a surveyor to wack each seacock to make sure it was installed solidly and worked easily. There's a good reason why the USCG requires routine replacement/inspection of seacocks. When they fail the results are often quite serious if not deadly.

The long and short of it is that if the offshore cruiser doesn't have seacocks that are readily identified as meeting US bronze standards then change them out. And don't hesitate to change house the hoses and clamps. There are other ways to economize.
But with the underwater gear.

I think you'll find that Beneteau uses DZR Brass thru-hulls and valves. DZR Brass is somewhat better than regular brass, but not much.

Hi Jim
You mentioned that you replaced the original through hull fittings with ones made of "pure brass". Unfortunately brass is a copper based alloy containing zinc and therefore you should expect continued corrosion. I hope you meant bronze, rather than zinc.