Ball Valve & Groco IBVF

[Idon84]

When we bought the Cosmic Dancer there were 3 thru hulls that were set up as ball valves screwed onto the thru hulls. Knowing that this is not the preferred method I set out to figure out what I was going to do.

I settled on trying the Groco IBVF because new seacocks were expensive and the ball valves I had were in great shape from Marine Hardware. www.marinehardware.com/

When I try to install the ball valve onto the IBVF I can only get 3 turns onto it (hand tight). Reading the info from Maine Sail’s site www.pbase.com/mainecruising/seacock_primer I see that the Groco Ball valve in the pictures doesn’t screw down onto the IBVF that far either.

So after all of this I took my IBVF’s down to West Marine to try a Groco ball valve to see how fare it would thread onto the IBVF. Again only about 3 turns (hand tight). So am I to guess this is normal?

The thru hull threads perfectly onto the ball valve 5 turns, better than it fits the IBVF (3 turns) and the same is true for the Groco ball valves.

Also the thru hull thread perfectly into the bottom of the IBVF, so no problem here.

Thoughts?

Has anyone ever heard of this Marine Hardware Co.? Good, Bad? The valves are heavy bronze with a SS ball.

[David]

Redmond, Washington is not exactly a boating center and the address in Ormond Beach seems to be someone's home. Sounds to me like you are trying to mix thread standards.

David

[Tim]

Ball valves, and the top threads of the IBFV, have tapered threads, so they are going to tighten before you bottom out the threads.

I don't know how many turns it normally takes, but you should expect there to still be exposed threads and not bottoming out the threads whenever you're installing something with tapered threads. Note that even Groco's own illustration of a completed setup shows exposed threads, much as you are suggesting your own does.

[Idon84]

That's my fear David, mismatched threads. I went to West Marine and tested the Groco ball valve to exactly duplicate the picture above. The Groco BV didn't go on any further either, so I guess this is normal as Tim points out. And I guess only time will tell how well those BVs from Marine Hardware last.

Thanks,

[David]

Bryon,

From what I can find on the subject of gaging for tapered threads, for a 1-1/2" OD pipe, it should take about 4-1/2 turns by hand and another 3-1/4 turns by wrench. So it sounds like that is close to what you have, right?

David

[Idon84]

YES that sound about right, 3-4 by hand and I'm sure I could get another couple with the wrench. I think it should be be fine, I was just a little confused because the thru hull threaded perfectly into the Ball Valve but the Ball Valve did not thread into the IBVF anywhere near as easy.

[Maine Sail]

YES that sound about right, 3-4 by hand and I'm sure I could get another couple with the wrench. I think it should be be fine, I was just a little confused because the thru hull threaded perfectly into the Ball Valve but the Ball Valve did not thread into the IBVF anywhere near as easy.

The threads on the bottom of the flange are NPS or straight thread as are the threads on a thru-hull. These are non-sealing threads and as such, like a nut and bolt, will thread on with little to no resistance.

The threads on the top side of the flange and the the threads on a ball valve are NPT or tapered threads. These are sealing threads and as such will tighten onto one another with increased resistance.

It is important to remember that each threading and tapping machine has slightly different tolerances as dies & taps wear so a ball valve by one maker may thread on slightly further, or less than one by another but it's really no big deal..

Using the flange gives you properly matched threads on the top and bottom..