How to seal a through hull fitting to a ball valve?

[West Coast]

Following on from my last post, I now have a shiny bronze 3/4" thru hull fitting and ball valve

I will get some good underwater sealant to seal the skin fitting through the hull, likely sikaflex 291.

However, my question is what is best sealant to use on the thread between the skin fitting and the ball valve?

 

[pvb]

If you're not bothered about getting it off again, use Sikaflex! Or use silicone and use a lock-nut to secure the valve in position.

 

[Billjratt]

I use soft stuff, so that I don't rip the skin fitting off the hull when I try to change the valve later. If you have to get a seal with the valve facing in a specific direction, it'll have to be teflon tape I guess.

 

[hairbox]

no no no

No do not use sikaflex it will not seal properly under pressure when you screw the two together use ptfe tape which will smear around the thread and prevent any metal to metal contact therefore no corrosion when moisture gets betwenn the threads which it will eventually.

 

[VicMallows]

Or PTFE tape; or liquid pipe sealant; or if its a classic old boat I guess you might choose traditional plumbers hemp and boss white.

 

[capetown]

I'd use 291 with a back nut so the lever can be positioned.

Also try to get as many threads engaged as possible.

Edit. pvb, beat me to it.

 

[VicS]

+ another one in favour of a back nut.

Almost any sealant you can think of will do the trick if you use a back nut to lock the valve onto the skin fitting.

Cue list of unsuitable sealants !

I'd not use tape. Its good for tapered threads but not for parallel ones.

 

[West Coast]

Thanks all - went out for a run and came back to find so many helpful replies