Broken Seacock
Hello everyone. I had a very nasty surprise last week when I tried to open the seacock in the toilets of our 41/022: it just broke under the handle (see picture). Looks like dezincification?? I thought these seacocks were bronze so should resist sea water corrosion. Have I done something wrong?? Is there any specific maintenance apart from cleaning and greasing every year, or should one use a specific grease. Should I change all my seacocks although the others look fine?? Thank you for any information, and happy new year to all.

It is very unusual but it may happen; consider that 30 years of life is quite a long time for any kind of seacock.
Looking at your picture it seems that there was an axial bore inside the square insert to which the handle is fixed. This is unusual and for sure it weakens a part subject to possible strong torsion.
Still from your picture, there appears to be a green/blue bleeding (copper sulfate) which should always be interpreted as a warning message. Bronze (of which your old seacocks are made) does not contain zinc but it contains copper which, in normal conditions, is not supposed to bleed like that.
My recommendation is: 1) try to find the reason of the bleeding, 2) keep the usual yearly maintenance already mentioned, 3) use the best grease you may find, and 4) never tighten the two bolts in order to avoid freezing the cone. Hand tightening is sufficient most of the time. If a seacock freezes, your experience confirms that it should be freed by pushing it with a rod from outside and never by forcing the handle.

Daniel, 411/004

Dear Philippe

Dear Philippe

Thank you Daniel and Professor for this quick reaction.

The hole is indeed in the center of the square which is hollow (not a very good design I agree). It broke just with a slight hand push! The spindle is the piece of wood I inserted to stop the leak. This seacock was never fully watertight despite numerous grindings with grinding paste so that could be part of the explanation? What worries me is not to know the cause, and wondering whether this is not going to happen to others. I have not used graphite grease.

Did other owners sometime have the same problem? It could be part of the answer...

I will definitely "shock" test the others, and I also have bought Blakes' grease as I ordered a new seacock. Have you heard about "zinc rich grease" which could offer some electolytic protection??

Kind regards.

Philippe

I am also curious to hear other people but for the time being I would not worry too much. Your experience suggests that it would be a good practice to inspect the bottom of the hollow part of the cone of all seacocks we have. It should be solid and almost flat, without axial bores that enter the square part reducing its effective cross section.
The inspection can be carried easily through the open lateral port of the cone. To become even more assured, one could measure the thickness of the bottom with a caliper; I expect it to be several millimeters.

Daniel, 411/004

Dear Philippe

Dear Daniel, and Professor,

here is another clue to what seems to me some sort of dezincification: a picture of the handle side of the square. No problem with the thickness but cristals were looking rather red (ie copper?) when they broke. I will definitely look at the possibility of putting zinc anodes, as some are no bigger than pencils and could possibly go in the middle of the cone of the seacock without interfering too much with the cross section. Unfortunaltely probably not for the toilets...

Thank you so much for exchanging ideas, despite the fact that I agree that more than 30 years in the seawater without problem is already a very good performance!

Dear Philippe

I continue being impressed by the presence of the axial bore; first of all, it should not be there.
I agree with Lars comment that it is likely that a past forcing of the seacock may have caused a small crack in the weakened square stem that revealed itself through the leak. In the long run the crack developed into the complete failure you experienced.
This is a good lesson to learn: always find the primary cause of any leak, even the smallest.

Daniel, 411/004

Dear Philippe

Nothing lasts for ever!  These Blakes seacocks are the best available. I fitted 3 to my last boat (steel) and they lasted 25 years with absolutely no problems. They are always easy to dis-assemble, unlike many modern alternatives. Just try some of the plastic ones!

The seacocks on my 41 have all been replaced with quarter turn stainless steel ball valves. These are quite good, but the use of stainless in sea water where there is no oxygen flow can result in corrosion.

 If I was you, I would replace the seacocks with new Blakes

regards Cosmo Little

We have now replaced this broken seacock by a new Blake bronze valve (I am also rather terrified by corrosion of stainless steel by oxygen deprivation!) I thought it would be interesting to share some information (and questions!).

1/ All Blake bronze valves are hollow at the level of the square where the handle is fitted, including the new ones. (Same thickness of metal all around...) see picture below.

2/ I believe that the primary reason for the breakage of this sea cock to happen was hammering of the cone, probably attempting to unblock the valve (following poor maintenance) which created a crack.

Now the question: following Lars suggestion I broke the cone with a hammer (which was not that difficult: as it seemed a littled bit brittle, but did not wish to do a comparison with the new one!). The grain of the metal looks a bit rosy, but sanding the cone gave it its original gold color. See second picture. Does this show some sort of desincification? That's for Lars??

All in all I fully agree that more than 30 years of good service is already a fine performance!