Ball Valve Seacocks

Ahoy BCC’rs , recently I found a problem with my Apollo Conbreaco ball valve seacocks.

During last winter boat lay-up, and winterization prep , I removed the little brass plugs on the side of the seacock body, to drain them .

I found that corrosion had attacked those plugs . Upon inspecting the plug itself , it looked to be made of yellow brass not silicon bronze like the body .

Ah Ha ! , could a U L Approved fitting have such a flaw ?

Well, it is a easy thing to make new silicon brnz plugs from a 3/8" silicon brnz bolt.

In the photo of the valve in West Marine catalog, you can see the brass to bronze color difference of the plug , Ouch !

I think those threads are tapered pipe threads, so a bolt won’t work. I’ve tried to find bronze plugs from my ball valve seacock and couldn’t—just ss or brass. I think ss will last longer than brass.

Hi Dan , you are correct that those screw in plugs on the Apollo Conbreco ball seacock valves , have 1/8" tapered pipe threads.

Since I already keep a 1/8" pipe die thread cutter on board , all that I needed was 3/8" silicon bronze rod , and thread that.

I had 3/8" x 5" silicon bronze hex head bolts on board too, so I threaded the shank or shoulder area and discarded the threaded , and hex head ends .

What got my goat was the yellow brass plug in a silicon bronze seacock body , corroding away , sight unseen .

Even just plain nickel plated steel would have been better than yellow brass. The Pardey’s use those I think , steel grease cups on their seacocks.

As for a SS plug , I don’t know , but I have had good results “marrying” SS and bronze , like SS clevis pins in a bronze toggle . or bronze bolts in my SS lifeline stanchion attachments , all above waterline uses .

Bronze seacocks are made from leaded brass alloys, such as red brass and semi-red brass - telephone conversations with manufacturers. Groco uses C85555 as does Davey and Co in England. C8555 is also know as gun metal - 85% copper, 5% lead, 5% tin, 5% zinc. Silicone bronze is not suitable for casting nor is aluminum bronze.

Yellow brass is a no-no is a marine service environment. The zinc in the brass sets up a galvanic couple with the copper. The zinc is changed to zinc ions and is removed from the brass leaving behind sintered copper.

The best seacocks are the old plug and barrel seacocks and Groco’s rubber coated plug valve seacocks.

Regardless of which seacock you have, all seacocks should be serviced once a year and opened and closed once a month. Ball valve seacocks are throw-away seacocks - Worthless in my opinion.


I think the forum has had this discussion before. I don’t agree with Rod that ball valve seacocks are “worthless”. Not as long lasting as tapered plug seacocks maybe if you’re willing to work on them, but there are other considerations.

The Groco rubber coated tapered plug seacocks require release of pressure before they can be opened or closed, so it’s a 2 step process. We found this tedious with seacocks we opened and closed frequently as in the head intake seacock. The head outlet is still the original 1981 Groco but isn’t used much. Groco no longer makes this design.

Sam used W-C tapered bronze seacocks on all other thru hulls on Shaula (1981). The tapered plug becomes worn or corroded (pitted) and leaks when closed. They can be restored by lapping with grinding compound, although I haven’t succeeded in this process. Our seacocks are in locations that make lapping in place very difficult. I gave up trying to lap a seacock in place. I had a spare replacement and took the easy way out.

Groco makes ball valve seacocks these days. I believe most if not all modern production boats use ball valve seacocks.

Doug, your manufacturing a bronze plug is excellent. I’m lazy and went with the SS plug. By the way, Perko uses the same brass plug in their raw water strainers and a SS plug works there too.
Dan Shaula BCC 59 1981

O M G , Dan , I totally for got about that yellow brass plug in my sea strainer , Ouch ! and T Y for the reminder .

Gee , Rod , that Marine Architect Bill Luther , who was working with and, in Bill Crelock’s office, circa 1985, was the one who approved ball valve seacocks in his boat construction specs . He told me that the offshore oil platform industry ( which he works for at times ) uses the ball valve seacocks and other ball valves in their rig plumbing because they hold up to corrosive conditions better .

When I replaced the lower SS bobstay chainplate, I had the time to replace all my factory installed rubberized, “T” handle tightening seacocks.
I didn’t like the seeping salt water from those seacocks .

When I see telltale green corrosion on and around seacocks I get worried , which is the case this time in which I discovered the leaks from the yellow brass plugs .

I think you are right about this seacock discussion on this forum , once before , sorry that I didn’t search the archives, before posting my concerns .