Thru hull fittings and valves….. dope or tape

[NYSail]

Hello all,

replacing a thru hull and valve today. In past just used pipe dope with no issues. Spoke with someone last night he said he uses only tape, then another guy said he uses both.

What is the preference here

thanks

Greg
s/v Souleil

 

[Ralph Johnstone]

he said he uses only tape,

Do NOT use only teflon tape. Teflon has earned its popularity because it's nice and tidy. It often times leaks under cooler temperatures because it does not "flow" into micro leaks in the threads whereas when hot, it does.

The ultimate thread sealant at all temps is a mix of teflon tape first followed by a light smear of Permatex #2. 100% success every time.

 

[NYSail]

Do NOT use only teflon tape. Teflon has earned its popularity because it's nice and tidy. It often times leaks under cooler temperatures because it does not "flow" into micro leaks in the threads whereas when hot, it does.

The ultimate thread sealant at all temps is a mix of teflon tape first followed by a light smear of Permatex #2. 100% success every time.

View attachment 237238​

Thanks!

I postponed installation today to get this…… I like the idea of this much more than regular pipe dope. even though I have never had an issue….. but especially because I have to position the valves and fittings in a specific way and most likely won’t be aligned as I need if I fully tighten them in. I need about a 1/4 turn of forgiveness on each (other than the skin fitting).

thanks!

 

[TrapperJohn]

I swear by this:

Used something similar when I worked at the power plant except that brand name would offer certification for nuclear piping. No need for tape. Just coat the threads lightly and leave the bead that forms from the squeeze out around the threads.

 

[Project_Mayhem]

I use Rectorseal #5 as it works on fuel, water and air lines. The small tube is easy to store in a crowded toolbox. I've used it above and below the waterline with no issues.

 

[higgs]

I now use both teflon and pipe dope after a plumber recommended that approach.

 

[thinwater]

It will only leak if there is something wrong with the threads. Make sure the threads are clean and properly mated (taper with taper, straight with straight). Dope and tape are both fine (no tape on close tolerance hydraulic and control systems).

 

[Hayden Watson]

I had 3 out of 4 leaking failures of the install of my Marelon Series 93 seacocks which have the straight buttress threads. I loosened them until the seacock was getting wobbly and leaking like crazy and smeared on old fashion pipe dope and retightened them. No more leaks in the past 5-years.

 

[Barnacle Bill]

Not sure if you are asking about pipe threads or thru-hull caulks. (You wrote: replacing a thru hull valve today). If a thru-hull caulk is what you are asking about, I would use a thiokol product like Life Calk or 3M's 101. They are designed to cure under water and are perfect for thru-hull applications. If you ever have to remove it, they are not adhesive type caulks which would make the job difficult or even impossible. You definitely don't want to use pipe thread tape material for sealing a thru hull in the hull.