Thread sealant for seacocks

[Little Dorrit]

I have dismantled two stainless seacocks (BSP 1.5" and 3/4") due to slight weeping through the threads. It appears the original sealant had deteriorated hence the problem. What are the currently accepted products and techniques/methods for sealing the threads when I reassemble them?.

 

[RJJ]

Many use sikaflex or other PU sealant.

I preferred Loctite 55, the stuff that looks like dental floss, which has the advantages of (1) no mess (2) doesn't go off (3) allows you to screw it up and "back off" if you need to change the angle (4) isn't adhesive, so you can undo it whenever you like.

The Trudesign fitting guide gives you a more complete menu of options.

 

[Baddox]

I had stainless through hulls and seacock that were weeping a rust colour so replaced them with Tru-design fittings last year.
The stainless through-hull and seacocks were so well stuck together that I ended up cutting the mushroom shape flange off, from outside the boat to remove them. Tru-design recommend Sikaflex 291i if you want to seal their fitting, including sealing them to stainless if you don’t intend to disassemble them.
Tru Design

 

[Little Dorrit]

I had stainless through hulls and seacock that were weeping a rust colour so replaced them with Tru-design fittings last year.
The stainless through-hull and seacocks were so well stuck together that I ended up cutting the mushroom shape flange off, from outside the boat to remove them. Tru-design recommend Sikaflex 291i if you want to seal their fitting, including sealing them to stainless if you don’t intend to disassemble them.
Tru Design

Yes, I'm not sure stainless is the best material as it suffers from crevice corrosion but they have been well installed and I think will have quite a few years life left if I seal the threads well.

 

[thinwater]

I assume you mean the threads between the fitting and the valve, not leaking around the fitting.

Teflon pipe sealant dope (not tape--tape is for tapered threads). It's a pipe. If you want something that cures, there are versions that get hard. As good as Sika is, it is not a pipe sealant.

 

[penfold]

The loctite website suggests 5331 is the ideal, but I've used 577 in the past purely as it's more readily available. 575 would likely also do fine.

 

[Elessar]

I have dismantled two stainless seacocks (BSP 1.5" and 3/4") due to slight weeping through the threads. It appears the original sealant had deteriorated hence the problem. What are the currently accepted products and techniques/methods for sealing the threads when I reassemble them?.

I use this.
Clessetite Thread Sealant 50ml Tube - Clesse UK
If your seacock has to end up in a certain place get an additional backing nut so you can make it tight at the right orientation.
Replaced all 8 seacocks last year using this. All good.

 

[ghostlymoron]

I've always used plumbers PTFE tape on threaded fittings with no problems.