[nightowle]

Searched old posts but found nothing as to whether I can use bronze ball valves on plastic through hulls. The through hulls are in good condition and I have bronze fittings from elsewhere, but not sure if these are compatible.

I would plan on using Teflon tape and thread compound to seat the bronze to the plastic.

 

[tager]

Oh come on! Plastic does not suffer from galvanic corrosion. As long as the threads go, you have nothing to worry about!

 

[nightowle]

I thought I may have remembered reading about the different expansion and contraction temps that these varying materials operate at.

 

[tager]

I wouldn't worry about it... the plastic through hull is above the waterline, right? I would trust marelon below the waterline, but it should have a seacock then, not a valve.

 

[nightowle]

no. a couple are below the water line and a couple are above, and given the limited access I wanted to go with valve vs. seacock right now. I know seacock is preferred.

 

[JimsCAL]

I believe the ball valve with have tapered pipe threads while the thru-hull will have straight threads. Not compatible.

 

[sailingdog]

First of all, you shouldn't be using PLASTIC through-hulls below the water line. The only "plastic" through hulls that are safe to use below the water line are the Marelon ones, which are glass reinforced nylon.

You can use Marelon through-hulls with bronze seacocks... but most sea cocks are NPT threaded while the through-hulls are NPS threaded. If you're going to do this, use a bronze flanged adapter instead... this will have female NPS threads on the bottom for the through-hull and male NPT threads on the top for the seacock.

Personally, I think that you'd be better off using Marelon valves with Marelon through-hulls....but if you don't maintain the Marelon valves properly, you will break the handles off of them when they seize up. The Marelon valves need to be exercised regularly—at least once a month—and greased once a year.