Moving seacock and valve

I'm in the middle of a bathroom makeover and I decided to move the water intake valve to a more suitable location. Since the actual hardware is still in very good shape I will be reusing it after a good cleanup. Now I simply wondering if I should use regular teflon when I screw the seacock and valve back together or something else?

My preference would be to use 3M 4200.

Teflon works and is easily replaced when a thru hull is removed from the seacock to inspect it while hauled.

The seacock is the valve (should be)...if it is not...might be a good time to do it with a true seacock and through hull. Don't forget a backing plate/mounting pad.

For screwing things together...a Teflon based pipe dope would be fine, or Teflon tape.

For sealant under the through hull and under the seacock, any underwater rated sealant is fine, many use 3M 4200.

Sorry, I meant thru hull and valve. I am planning to install a backing plate indeed. I have teflon paste that I was going to use but figured I should ask to be sure it's ok. Looks like it is. 3M 4200 for the under water part for sure. Thanks.

Fotoman said:

Sorry, I meant thru hull and valve. I am planning to install a backing plate indeed. I have teflon paste that I was going to use but figured I should ask to be sure it's ok. Looks like it is. 3M 4200 for the under water part for sure. Thanks.

Click to expand...

I hate insulting other members experience...but I am amazed at how many plain ball valve on thru hull installs exist.

Have fun!

Happens every day. Nothing wrong with a ball valve per say it's how it's installed. Mis-matching threads (straight vs tapered) is issue. Groco makes a great device that's part seacock flange and has NPT for attaching a ball valve. This allows one to properly attach with a backing plate to the hull and use a standard full flow ball valve for an easy to maintain system. Attaching a NPT ball valve directly to a through hull fitting is just plain wrong.

Tapered pipe threads distort to create a seal when installed. When reusing tapered fittings the pipe dont get to seal as well so a high bulk sealer such as 4200 is what I would use instead of Teflon tape.

@ Fotoman, read, heed, and need. All wrapped up in a very informative piece.


Replacing Thru-Hulls and Seacocks Photo Gallery by Compass Marine How To at pbase.com


The MOST important thing to learn is the definitions of pipe thread.


NPS is: National Pipethread Straight. l l


NPT is: National Pipethread Tapered. \ /



Using these simple diagrams you can see the two surfaces do not mate for more than a couple threads. Bad JuJu on a boat.

You can screw NPT into NPS, BUt not the other way around. However, the connection (as described by Compass marine is extremely low quality, and risky for underwater thru hulls. In reality only two threads are fully engaged when doing this type of connection.


The mentioned Groco adapter (or actual Groco or Conbraco adapter WITH integrated valve) is FAR superior. I used the adapter WITH valve, since it eliminates one more threaded connection between the spud and the valve.


To bring the discussion back to the reality, do you REALLY want an imperfect partially threaded connection between the valve and the ocean, depending on it's integrity as an inferior connection? Don't just screw on a valve to the mushroom spud.


Make sure you read all the way to page 2! It's enlightening.

Only a few ball valves have a flange that will allow it to be BOLTED into the hull.

The other hassle with ball valves is the operating screw is usually made from easy to machine BRASS , not bronze .

So the operating rod is slowly dissolving if below the WL.

The tried and true tapered sea cocks are harder to instal, but easy to maintain , and easy to overhaul.

I have seen ones on 1930's boats , still in service .

Ball valves can be fine if well above a heeled water line and never submerged.

As has been stated, now is the time to up grade to a real flanged seacock or to add a Groco flanged adapter between the thru-hull and the valve. The Groco premade fiberglass backing plates are real time savers.

Unless you know its age, would suggest replacing the through hull. It's one of those things I wouldn't reuse. How old is the original one?


Jim
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