Through-Hull/Ball Valve Thread Mismatch -- Urban Legend?

[Manateeman]

There is a poster who tests anchors by video under real conditions and it looks like a lot of sailors appreciated his hard work. So I propose the following.
A straight pull test to destruction. You could easily get old sections of glass hulls with and without core, or a wood or an aluminum panel. Pop in the whole shooting match and tie it to a winch with a weight cell in the middle.
Destructive testing is so much fun.
Happy trails to you
Mark and the bored manatees

[sailjumanji]

Originally Posted by Dockhead

Sounds reasonable.


But Groco make a through-hull fitting with combination straight/tapered thread which can have a ball valve screwed directly to it, in case you prefer to do it that way.

Our new boat has Marelon fittings. Its a Marelon thru hull with a Marelon ball valve attached. At launch, the black water tank thru hull valve leaked at the handle. I thought a simple valve replacement. Seawind pulled the boat and replaced both the Marelon thru hull and valve. Said Marelon recommended replacing both and wouldn't warranty if just valve replaced.

[Dockhead]

Originally Posted by Manateeman

There is a poster who tests anchors by video under real conditions and it looks like a lot of sailors appreciated his hard work. So I propose the following.
A straight pull test to destruction. You could easily get old sections of glass hulls with and without core, or a wood or an aluminum panel. Pop in the whole shooting match and tie it to a winch with a weight cell in the middle.
Destructive testing is so much fun.
Happy trails to you
Mark and the bored manatees

MaineSail already did this, and the results are published on his site "Marine Howto" or whatever it's called.

He tested NPT/NPS throughhull/ball valve combos and found them to be some 20% weaker than ball valves screwed to the Groco flanged adapter, IIRC. As we've discussed, BSPT/BSPP joints are designed to screw together, so ought to be a lot stronger. Whether it's worth 20% (or 10% or whatever) of extra strength, to have three extra holes in your boat per sea cock and all the extra trouble, is up to each individual sailor. It's a choice that is basically never made in Europe. You can consider that all European sailors and all European boat builders are idiots, but I would politely disagree.

My personal opinion is that the Groco flanged adapters are a pretty good solution -- much better than the so-called "proper sea cock". Because you can screw the valve off them if you need to replace the valve, which inevitably happens with ball valves sooner or later (as opposed to tapered cone valves, which can be endlessly rebuilt). For sure this is stronger, so might be worth the extra holes, at least, if you're building a new boat and have a guaranteed core-free piece of hull to put these holes through. "Proper sea cocks" I wouldn't have on my boat. But that's just my opinion; everyone obviously is entitled to his own, different one.


Another choice is tapered cone valves vs. ball valves. Some traditionalists swear by tapered cone valves, calling anything else "not proper". I had tapered cones on my first boat. They are beautiful and last forever, but they require a fair amount of maintenance. If you let them go for more than 2 or 3 years without lapping the cones they get messy. Ball valves on the other hand are maintenance free, and quality ones last about 20 years. For most of us without hired labor on board, with plenty of other jobs on the maintenance list, this is a no-brainer. I can't even imagine what lapping the cones on 15 sea cocks would be like

[GordMay]

Originally Posted by Dockhead

... My personal opinion is that the Groco flanged adapters are a pretty good solution -- much better than the so-called "proper sea cock". Because you can screw the valve off them if you need to replace the valve, which inevitably happens with ball valves sooner or later (as opposed to tapered cone valves, which can be endlessly rebuilt)...
... Another choice is tapered cone valves vs. ball valves. Some traditionalists swear by tapered cone valves, calling anything else "not proper". I had tapered cones on my first boat. They are beautiful and last forever, but they require a fair amount of maintenance. If you let them go for more than 2 or 3 years without lapping the cones they get messy. Ball valves on the other hand are maintenance free, and quality ones last about 20 years. For most of us without hired labor on board, with plenty of other jobs on the maintenance list, this is a no-brainer. I can't even imagine what lapping the cones on 15 sea cocks would be like

Don’t most folks remove their tapered cone valves for cone lapping? IDNK, never done it.
➥ https://www.cruisersforum.com/forums...ml#post2151368

[vpbarkley]

Just an aside, you can purchase a NPS tap (straight thread). Then it's easy to convert a female NPT valve (tapered thread) into NPS (straight thread).

Google search "straight pipe tap".

[Cadence]

Originally Posted by Q Xopa

Hmmm interestiong and strongly stated opinion.

I am assuming its the tapered threads you dont like?

What is your opinion of what Tapered threads are designed for?

So if I understand your comment correctly you like relying on pipe dope and telfon tape to seal on straight threads, so no actual mechanical metal sealing?

No, tapered pipe thread is great as long as the male and female are tapered. Mixing pipe thread (tapered) with a straight thread is what I can't see.

[Q Xopa]

Originally Posted by Cadence

No, tapered pipe thread is great as long as the male and female are tapered. Mixing pipe thread (tapered) with a straight thread is what I can't see.

Ok, I haven't heard of that before. We are never too old to learn eh.

Trade school was a while back for me but I seem to recall we were told screwing a tapered thread in to straight/ parallel threads was the typical way to best seal on threads. Pipe dope or teflon tape still required. As you screw it in it wedges in tighter like a tapered bung.

[Dockhead]

Originally Posted by GordMay

Don’t most folks remove their tapered cone valves for cone lapping? IDNK, never done it.
➥ https://www.cruisersforum.com/forums...ml#post2151368

The valves are typically not separate (that's what makes it a so-called "proper sea cock"), so this would be a huge operation. No, you pull the cone out and lap it in place. At least the ones I used to have.

[Orion Jim]

Originally Posted by GordMay

Don’t most folks remove their tapered cone valves for cone lapping? IDNK, never done it.
➥ https://www.cruisersforum.com/forums...ml#post2151368

I still have all of my original equipment Spartan tapered cone seacocks. After 36 years none has ever leaked or been lapped. There is no indication of the cones being “wasp waisted” or any indication of galvanic corrosion. Every two seasons I dismantle them and service them.

https://marinehowto.com/servicing-ta...cone-seacocks/

[Manateeman]

Bench test. I remember the MarineHowTo.com test and just looked at again.
Great work. He didn’t test plastic and he didn’t test systems available outside the US. One pull direction parallel to the hull..ok...but my idea of a real world test would include a battery swinging on a rope pendulum. Probably the best test suggestions will come from boating moms.
Engineers were once children who failed putting it back together so mom won’t notice. Doctors were once children who were fascinated by how mom could drive to the hospital faster than the police. Soccer moms really understand storm damage. They gave birth to hurricanes.
Happy trails to you
Captain Mark and his afternoon nap manatees.

[john manning]

Screw threads are not designed to be seals. They are a method for making a mechanical attachment. The reason for matching threads is so that the attachment can be strong. It is also makes separating them later much easier.

Engineering specifications relating to threads will always require the use of a thread sealant or a sealing washer if a pressure seal is required.

What is hard about matching threads.

[Cadence]

Originally Posted by john manning

Screw threads are not designed to be seals. They are a method for making a mechanical attachment. The reason for matching threads is so that the attachment can be strong. It is also makes separating them later much easier.

Engineering specifications relating to threads will always require the use of a thread sealant or a sealing washer if a pressure seal is required.

What is hard about matching threads.

[David Mathis]

A few years ago I had a slow leak in a ball valve at the handle but was unable to find a replacement valve. A person with far more marine plumbing experience than I ever hoped to have told me to wait until the end of the boating season when the boat is hauled and blocked to wait out the snow and ice in northern New York, then go to the local hardware store and get the right size ball valve. Remove the leaking valve and try screwing on the new one. If it bottoms out, you just wasted your money. However, if there are enough threads to get it tight, just apply thread sealant and screw it on, provided the thru hill doesn't need the valve base pressure to secure it into the hull. Yes, the material is slightly different so in about ten years in the salt, the valve will have to be changed again. With summers spent on the Hudson River and Lake Champlain, the valve is still good after many years. Why are some threads tapered and others straight? Perhaps it's the engineering equivalent of "Girls Gone wild".

[Dockhead]

Originally Posted by john manning

Screw threads are not designed to be seals. They are a method for making a mechanical attachment. The reason for matching threads is so that the attachment can be strong. It is also makes separating them later much easier.

Engineering specifications relating to threads will always require the use of a thread sealant or a sealing washer if a pressure seal is required.

What is hard about matching threads.

Well, nothing in this post is actually true.

Taper-to-taper joints are intended to make a seal -- that's their whole purpose. The fact that they require thread sealant doesn't take away from this. The seal in taper-to-taper joints takes place in the threads.

Parallel-to-parallel joints don't seal in the threads -- they seal where the end of the female treaded part bottoms out against the female threaded part, and these need a washer to seal.

Neither of these types is adjustable -- the ball valve will go where it goes, so you can't adjust where the handle will be or where the outlet will point.

Which is the reason for the existence of the male taper > female parallel joint. In this type of joint, the seal is in the threads. But the the threads don't jam suddenly into each other like a taper > taper joint. They jam up gradually and you have some adjustment. Like the taper > taper joint, you need thread sealant.

As explained in Wiki:

"Two types of threads are distinguished:Parallel (straight) threads, British Standard Pipe Parallel thread (BSPP. . ), which have a constant diameter . . . Taper threads, British Standard Pipe Taper thread (BSPT), whose diameter increases or decreases along the length of the thread . . . These can be combined into two types of joints:

"Jointing threadsThese are pipe threads where pressure-tightness is made through the mating of two threads together. They always use a taper male thread, but can have either parallel or taper female threads. (In Europe, taper female pipe threads are not commonly used.)"Longscrew threadsThese are parallel pipe threads used where a pressure-tight joint is achieved by the compression of a soft material (such as an o-ring seal or a washer) between the end face of the male thread and a socket or nipple face, with the tightening of a backnut."
https://en.wikipedia.org/wiki/British_Standard_Pipe

As has been posted above, male taper > female parallel is a specifically designed and approved joint according to European Standard UNI EN 10226-1; see http://www.sarm.am/docs/10226-1-2004.pdf. BSP threaded pipes are designed to be screwed together this way male taper, female straight.

Here is a handy diagram showing which types of male BSP threads are compatible with which types of female ones:



https://www.nxymarine.com/blog/the-d...spt-thread_b14

Originally Posted by Uncle Bob

. . . I checked with my go to supplier of marine bits n pieces and his comment was that all ball valves that he sells, be they stainless or bronze, are parallel threads as are the through hulls, so down here at least they play well together.
Cheers.

He's right that they "play well together" -- they are BSP. But I doubt his through hull fittings are straight thread. I've never seen a BSP through hull fitting with straight threads; I don't believe they exist. Do your through hull fittings screw all the way down? Do they have washers? If not, then your through hulls have taper threads.

These, for example, are BSPT: Guidi Thru-hull Connection 1260

Note that parallel > parallel requires a washer:



male taper > female parallel does NOT require a washer -- the seal is made in the threads.

[Wotname]

FWIW

I recently got a bunch of irrigation fittings (all BSP). Prompted by this thread, I had a closer look at the threads.

ALL the female threads were straight.
ALL the male threads were tapered.
This were common fittings available anywhere in Australia.

So I next visited the local chandlery and checked a bunch of the marine pipe fittings (SS, bronze and composite). Of course they were BSP and likewise all the female were straight and all males were tapered except the male skin fittings (mushroom style) which were all straight.

Everyone I know uses tape on the threads or a jointing paste or like me, both.