what's the best way to seal thru-hull/seacock threads?

[gtunison]

Is tfe paste adequate for sealing threads for thru-hull/seacock connections? Does anyone have a favorite brand or type to recommend?I just talked to a guy at a boatyard who said he doesn't like using fittings that are not tapered because they are prone to leaking when the valve handle is wiggled during normal use, but he said it would not leak if installed by him. He recommended using just the nut to hold the thru-hull in place with a bronze non-flanged valve. If I'm just sailing on a small lake do I really need a flanged seacock?
Thanks

[US27inKS]

Paste worked great for me. It's a lot more reliable than tape, and it is made for that job unlike other sealers. If you want to know what the best brand is, call a plumber. It's their job to seal pipe threads without the job coming back to bite them. A good plumber will insist on the best sealant.

[CalebD]

Check mainesail/haleikai's website for lots of useful info by someone who has been there, done that and we are waiting for the movie.
Seacock & Thru-Hull Primer/Pre Information Photo Gallery by Maine Sailing at pbase.com
It is a nice resource with plenty of photos of how the hardware should be put together.

[sailingdog]

A better page would be Halekai's article on actually replacing seacocks and through-hulls. Sealant, like 3M 4200, should be used on the flanged base and on the throughhull itself—as seen in his photos.

The plumber's putty might be good on a pipe...but not so good for use on a through-hull IMHO. If the seal between the through-hull itself starts to leak, rather than the threaded connection, the plumbers putty will do nothing to stop it from entering the boat. Putting a good bead of sealant under the base of the flange, in addition to plumbers putty on the threads, will stop the water—whether it is coming down from the threaded bit or up from the a leaking through-hull bedding job... a much better idea IMHO.

[Maine Sail]

If you're using mismatched threads, not highly recommended but will and has worked for many, I prefer to use both tape and dope together.

Try the yellow "gas grade" teflon tape then wipe on some Hercules Real-Tuff pipe dope over that (can get it at Home Depot). If not using both use just the dope rather than tape..

[gtunison]

Thanks for the great answers to my questions.
Why would the yard guy like to use mismatched threads and the supplied locknut instead of the flanged thru-hull? He also seemed to not believe I got a ball valve with winterization drains. Is there a school people go to for learning how to proffesionaly repair and maintain boats?

[Stillraining]

Originally Posted by gtunison

Is there a school people go to for learning how to proffesionaly repair and maintain boats?

Ya.. its called trial and error school..the trick is finding a yard that has all the trials and errors out of the way already...

[SEMIJim]

Originally Posted by gtunison

Why would the yard guy like to use mismatched threads and the supplied locknut instead of the flanged thru-hull?

They may not necessarily be mismatched. For example: Groco TH-series thru-hulls have a "Combination Thread" on the tip that incorporates the NPT end. So as long as you don't cut one of those down, you can thread an NPT fitting on the end.

Jim

[gtunison]

that's a cool idea but he specifically said "see how these taper down and seal so soon. the straight threads sometimes start to seep after a while of moving the handle back and forth." who to trust? he did assure me he could do it either way and seal it.