[johnharch]

Awhile back there was a thread on this on pacificseacraftowners.org ? View topic - corroding seacock drain plugs
Since I have an interest in this and there is very little activity on the pacificseacraftowners site, I'm bringing it up here.

One of my drain plugs on a cockpit scupper seacock has clearly been leaking slightly, as evidenced by the thick build up of verdigris around it. Do you think this is something I should be worried about?

 

[aa3jy]

Pics?

 

[johnharch]

Unfortunately I cleaned it all up before I thought to try to get a picture of it.

 

[johnharch]

Here is a picture after getting it mostly cleaned up.

https://lh6.googleusercontent.com/-...ANug/lM-3IVkvxOM/s640/IMG_20150224_145925.jpg

 

[ralopata]

John:

I don't know one way or the other, but is it possible this is a result of oxidation from the presence of moisture in the locker rather than a leak? Was that green oxidation concentrated at any particular point on the seacock body that would indicate a water source?

Don't know, just brainstorming...

Roger Lopata
JUNO
PSC 40 -- #46

 

[johnharch]

Oh yes, it was very clearly associated with the drain plug. It was concentrated around and below it. My bigger concern was that it was indicative of galvanic corrosion and was going to get worse, but now that it is cleaned up, it doesn't look so bad. I may pull the plug out and inspect it at the next haul out, but it is a royal pain for me to get a hand on it.

 

[RainDog]

I believe is you have a galvanic issue the bronze will turn pink, not green.

Example photo: http://www.powerandmotoryacht.com/hull/confirming-continuity-page-2

 

[PSC31]

John,

I also had a slow leak in my galley sink drain. I pulled the plug to find the threads pretty much gone; surprising enough it was holding its place and putting the plug back in there simply wasn't an option. I don't know if a slow leak from a seacock is normal or needs maintenance/replacement, but the leakage was coming from the seacock itself.

I tapped new threads into the seacock side as a temporary fix. The next size above was for a 10M bolt(pilot hole for 8M is smaller than 1/4", if I recall correctly). A 15mm zinc plated bolt with 2 bronze washers kept the bolt itself from hindering the ball valve's movement.

That was 4 months or so ago and it's been behaving well... Well, so far, at least.

 

[johnharch]

Raindog, I agree the green comes from moisture, in my experience, salt water. Galvanic problems will turn it pink. My concern is that the leakage that is turning it green is caused by corrosion of the plug and I really can't tell what color it is without pulling it.

PSC31, that sounds like my issue and what I feared. I guess I'll have to break down and pull the plug when I haul, but it is in an incredibly awkward spot to work on.

thanks for the feedback

 

[PSC31]

john,

quick fyi edit: bolt had a nut and two washers on it. nut measured 7.7mm and washers 1mm each, so bolt cant enter the seacock for more than 5mms.

 

[Lantau]

john,

quick fyi edit: bolt had a nut and two washers on it. nut measured 7.7mm and washers 1mm each, so bolt cant enter the seacock for more than 5mms.

If the 'problem' is the same as in the sink drain photo of PSC31's boat, I think there's nothing at all to worry about -- unless you care greatly about the cosmetics of things under the sink. There's no sign of stray electricity there; that's just bronze in seawater for you. The outside of every seacock would appear the same greenish color were it not for being hidden under bottom paint. Indeed, to me the unsightly green is a sign that you have good-quality seacocks (copper is definitely forged into the metal). The solution would be to never use seawater in the sink, some of which invariably will get under the sink (just like water can do at home) and of course it passes through the seacock. My assumption is that all of our seacocks below the water line have similar green appearance internally -- but of course we can't see it (out of sight, out of mind, which in this case is OK).

Just my two cents worth...

 

[hopcar]

John, your seacock looks like it is an Apollo brand seacock. The drain plug is just a regular brass 1/8" pipe plug and is subject to dezincification over time. It can take many years to become a problem and they cost only about a buck at any marine or hardware store. Pull the plug and look at it. If it looks bad replace it. The rest of your seacock is bronze and should be fine.

You don't need to wait to haul to pull the drain plug. With the seacock open very little if any water will come out. With the seacock closed only a few ounces will come out.
The seacock will continue to function normally whether the plug is in or not.

 

[johnharch]

Thank you Hopcar, that is what I have been thinking. The drain plug is centered on the ball, so it should be sealed from the outside. I am, however, certain that my plugs are bronze, not brass. At any rate, I'll wait until I haul to look at it. The thought of breaking something while I'm stuck in that hole with water coming in makes me quiver. In the meantime I'll look around for a bronze plug.

 

[hopcar]

Let me know if you find a 1/8" plug in bronze. All of the ones I see look to be yellow brass.
If you drill it out and go up to 1/4" you can easily find red brass / bronze plugs. It really isn't worth the effort unless the threads in the seacock body are damaged. Even if the plug fails completely, it won't sink your boat.

 

[johnharch]

Here you go:
Plug Square Head 1/8"" Bronze

 

[johnharch]

I checked with Hamilton and they assure me that they are in fact bronze and not brass. They are also available from Fisheries Supply in Seattle and I see them listed on Amazon as well. Unfortunately, I'll pay more for the shipping that for the plugs.