skin fittings and ball valves

[abbott013]

Hi all, Advise needed here. 5 years ago i bought brass skin fittings and chromed brass ball valves with stainless handles for my yacht, these fittings are below the water line and service cockpit and sink drains. one has developed a slight leak where the ball valve meets the skin fitting and they all look to be white and crusty around the joints. Am i going to have to replace the hole lot with bronze skin and dzr ball valves ?.
I will add when i bought these they were marked iso9093 so i thought they were safe.

 

[VicS]

Iso 9093 I think you will find requires only 5 years resistance to corrosion.
Its the standard that allows manufacturers to fit ordinary brass below the waterline.

Time therefore to consider replacing them all, or at least subjecting them to a very critical examination on a regular basis.

Your choice whether to fit brass again, with an expected 5 year life, or replace with bronze/gun metal or DZR which should last almost indefinitely

 

[abbott013]

Thanks vic, I did'nt know the iso covered the fittings for 5 years, its looking like the boat is coming out again. can i ask you how you seal the thread between skin fitting and ball valve. i always find parallel threads a problem.

 

[VicS]

Thanks vic, I did'nt know the iso covered the fittings for 5 years, its looking like the boat is coming out again. can i ask you how you seal the thread between skin fitting and ball valve. i always find parallel threads a problem.

I have not found a copy of the iso online ( and they cost an arm and a leg to buy) but following some links lead me to my conclusion about the 5 years .. in particular the references to the iso in The MAIB investigation into the near loss of the FV Random Harvest a few years ago

The international standard for metallic seacocks and through-hull fittings on small craft,
I S 0 9093-1: 1994, states: “The materials used shall be corrosion-resistant ........” and
defines corrosion-resistant as: “a material used for a fitting which, within a service time
of five years, does not display any defect that will impair tightness, strength or
function.”.

I would fit a lock nut so that the valve can be postively locked in the required position on the skin fitting. ie so that its handle points in the direction you want it to.

Almost any jointing compound or sealant applied to the threads could be used to make the joint water tight.

 

[prv]

Almost any jointing compound or sealant applied to the threads could be used to make the joint water tight.

I use some Loctite stuff that comes in a red bottle with a bellows squeezy bottom section. It's worked perfectly to seal various parallel threads in my bathroom plumbing, which is all at fairly high mains pressure - much more than a seacock will be required to cope with.

Afraid I can't remember the name though.

Pete

 

[VicS]

I use some Loctite stuff that comes in a red bottle with a bellows squeezy bottom section. It's worked perfectly to seal various parallel threads in my bathroom plumbing, which is all at fairly high mains pressure - much more than a seacock will be required to cope with.

Afraid I can't remember the name though.

Pete

or

 

[prv]

That's the badger.

Pete

 

[Halo]

I suggest gun metal or bronze skin fittings with an anti rotation knib. Seal with silkaflex - initially only tighten lock nut finger tight then "nip up" once the silkflex has cured.
Personally I allways use stainless 316 ball valves and fittings - brass not good enough in my huble opinion
On my last boat this material combination worked for 15 years with no issues at all

I replaced my head discharge skin fitting and ball valve last month and it had previously been gummed up with the loctite stuff described above. This made it hard to disassemble and I could not shift it until i warmed it with a fan heater. In the end I took the easy route and removed the old skin fitting by carefully grinding away the flange/tube joint with an angle grinder - from outside the boat. The flange fell off and whole assembly was easily pulled into the boat

I got gunmetal and 316 fittings from asap supplies - good value and service (NO CONNECTION)
Good luck
Martin