Sealing Transom Drain Bung

[npm108]

I have a stainless steel thru-transom bilge drain that has a screw fit drain bung. The previous owner used Teflon tape to seal the threads but didn't do a very good job as I found it leaking when I launched the boat.

Is it safe to use Teflon Tape in Salt Water under the water line on these kind of screw bungs or should I be using something else?

[Dirk Diggler]

Have you a photo, maybe you could use an O ring.

[Al Baker]

An O ring would be a good idea. I would also be tempted to trailer it and part fill the hull with water to see if that's the source of the leak.

[npm108]

Thanks for the tips.

I'll take a pic but if memory serves me well it doesn't have a lip for an O-Ring Application, but will bring the part up from the garage with me as its currently taped to the hitch so I don't forget it's out!

[npm108]

There doesn't seem to be much in the way of a lip for an O-Ring to seal with. I've removed most of the messy Teflon tape that there was....

Side View
Outside in (Top Down)
Inside Part Out (Bottom view)

[colcreate]

That's a taper plug, BSPT. It relies on squeezing a compound (either tape or chemical) between the threads of the progressively larger diameter plug being screwed into a parallel threaded bore. If you need to frequently unscrew the plug it might be better to replace it with a flanged plug that can accept a gasket seal or O ring.

[npm108]

Thanks Colcreate. I don't need to remove it on a regular basis perhaps once a year at most as I am happy to use the bilge pump and then sponge to get rid of any remaining water. The Deck has its own scuppers.

Do you think a chemical compound like Loctite 567 would be better than thread tape? Boat stays in the water for 4 months in summer so I need something safe/good.

Perhaps there is a product you can recommend?

Nick

[Wightdiver]

PTFE Tape (white plumbers tape) should work fine, no issues with salt water and if it can hold water in a pressurised heating system for years without a problem it will certainly work on a bung.

It’s cheap too!

Andy

[jyasaki]

If you're not going to remove it regularly (I use a similar plug, though mine is a hex head SS plug), I'd go with what's commonly known as Plumber's Putty. Easier to apply than teflon tape (smear it on the threads and insert plug), should not need reapplication after removal (probably), and not much more expensive.

jky

[gasman]

[QUOTE=npm108;498294]Thanks Colcreate. I don't need to remove it on a regular basis perhaps once a year at most as I am happy to use the bilge pump and then sponge to get rid of any remaining water. The Deck has its own scuppers.

Do you think a chemical compound like Loctite 567 would be better than thread tape? Boat stays in the water for 4 months in summer so I need something safe/good.

Perhaps there is a product you can recommend?

Hi. Use 'single wrap' PTFE tape. It's a lot thicker than the standard tape, and it a lot better. Don't be tempted to wind to much on the threads though. 1/2 overlap will be fine. I use it and havn't had any trouble.

Ian

[colcreate]

PTFE tape is probably the easiest to re-apply. Cheap as chips, easy to use just wrap it in the direction of the threads (so it doesn't unwind as you screw it in) and it doesn't go off or leak in your toolbox.....

[Nightfisher]

You may be able to find a simple expandable rubber transom drain hole plug if you wish to remove frequently. It has a metal tab on the end that when pushed the wall of the plug expands sealing the opening. Though I'm not sure if it would work on a pipe-threaded port.