Thread sealant for seacock ball valve?

[er9]

Originally Posted by mvweebles

I'm a bit confused, but probably just semantics. To me, thru-hull is a somewhat generic term. A common configuration is a mushroom thru-hull with straight thread stem. On the inside is the valve - I typically use the term "thru hull" for the entire assembly.

The Groco adapter plate (which I assume is what is being discussed) appears to be an un-valved method to transition from straight thread to NPT to allow installation of a ball valve. The broad triangle base is clearly stronger than mounting a ball valve directly to the stem of the mushroom fitting, but my confusion comes in mounting the triangular base plate requires same work as mounting a proper seacock and cannot be done properly with boat in the water.

I must be missing something. I'm redoing thru hulls as we speak so interested in feedback. Though I am a fan of well-backed seacocks.

https://www.groco.net/products/fitti...flange-adaptor

Correct it just converts NPS to NPT. I'm going to haul out the boat to mount the thru hull and base properly but once that's done, in the future you could replace the valve that threads onto the triangle base while in the water by simply plugging the thru hull from the outside.

[er9]

Originally Posted by Dockhead

If I had known this earlier than just this year, it would have saved me a heap of grief


I just replaced half the ball valves on my boat this year and did a lot of research on this question.


According to my research, best practice seems to be one of two things:


(a) tape AND thread sealing paste
(b) thread sealing paste AND hemp fibers



I used some of both techniques, with good results.

I've heard this mentioned more than a few times now since researching this myself and...since I ordered both to try, I'm thinking this may be the way to go.

[er9]

Originally Posted by mvweebles

I do not understand the Sailors love affair with ball valves on mushroom thru hull fittings, or even these improved adapter plates. I simply do not understand the desire to replace a strong and reliable seacock with a weaker, inferior, and more vulnerable ball valve simply because it might be easier to replace in 20 years. I just don't get it. I also do not understand the recommendation to avoid putting some sort of thread sealant on a NPT fitting. It may make sense on a spec sheet, but relying on an interference fit, especially where access may be compromised, seems like an academic vs real world recommendation.

Peter

Yeah I agree that's why the one of the only two ball valves on my boat is getting replaced with this lovely beast. The raw water intake will get the new groco because I dont think I can fit even a 3/4 spartan in there.

[Dockhead]

Originally Posted by a64pilot

Straight threads are always used for mechanical fastening, the reason is you are trying to stretch a bolt and or provide a clamping force, if you used tapered threads then there is only a small length you can tighten until the threads essentially seize, and you may not have applied any clamping force and unless your using a pre load indicating washer etc you couldn’t measure clamping force.

However with plumbing an interference fit is desired, because while mechanical strength is desired, your really after a leak proof fit. So all, threads in plumbing where the pipe fit up is what provides the seal, are always an interference fit, straight threads are never used, not unless the threads are not the seal, like an O ring or ferrule for instance.

So the actual thru hull is a mechanical fastening, your compressing the nut or whatever is used to clamp onto the hull and backing plate, so straight threads are used or should be, because that’s the correct thread for the task.
However the ball valve is a plumbing connection and therefore should be an interference fit.

Think of it this way, screwing a ball valve onto a straight thread part and expecting the pipe sealant to hold it in place, is exactly the same thing as screwing a nut onto a bolt and expecting the nut to be held into place by Teflon tape or pipe dope, it’s not being held securely at all, but can’t back itself off because you have a hose on it, but it’s not very secure and the only thing keeping it from leaking is the sealant, you would never get away with this on any system that has significant pressure, you get away with it on a thru hull because the pressure is very low.
Then you need to realize what keeps things you put together by tightening nuts or boots is that your stretching the bolt or stud etc, that’s why they don’t suddenly loosen, they gradually loosen because that stretch is coming off as the nut is turned, but your not getting any of that with straight threads not bottomed out, and bottoming out is incorrect too, because there isn’t enough length of anything to get any stretch, it’s just jammed.

So the ideal is of course straight threads where mechanical fastening is needed (thru hull against the hull) but you should transition to tapered threads when it becomes a plumbing part (the ball valve)

The adapter does that, it’s straight threaded where that’s correct, and tapered when that’s the correct thread.

Strength wise, I feel certain that the adapter and the thru hull is stronger than any fiberglass hull, and if a G10 backing plate is used, then the whole thing is enormously strong.

They way most boats are built it’s a thru hull with a ball valve screwed onto it, whether it’s straight or pipe threads the thru hull itself is the weakest point, if not the hull because a piece of plywood is often used for a backing plate and plywood is weak in compression, especially after it’s been wet for a few years.
A seacock removes that weak point by the flange on the seacock bearing the load, but requires the boat to be pulled to change out.

The adapter is as strong as a seacock because it’s the same flange, but gives back the ability to change the valve without pulling the boat and changing the whole thing.

Straight threaded valves were the best option before the adapter because at least you were getting a lot of thread into the valve, so the joint was strong, putting an NPT valve onto straight threads, it’s likely that only a very few threads were into the valve and with only a few threads in, it wasn’t very strong. So while being incorrect from a plumbing perspective and much more likely to leak, at least there was enough thread engagement so the valve won’t break off if stepped on, so it was the lesser of two evils.

But the adapter allows the correct thread to be used for the correct job, interference fit for plumbing, and straight for mechanical fastening.

If you wanted to use a straight thread valve on a straight thread thru hull, then you should use a jam nut so that when it’s positioned where you want it, the jam nut can be tightened to hold things in place and your not relying on sealant to mechanically secure anything.

Makes perfect sense; thanks.


So it looks like we're missing jam nuts? I've never seen a jam nut on a skin fitting/ball valve connection. European boats without any exception (except perhaps the retro Rustler yachts which I believe have Blake's tapered cone sea cocks) have straight thread BSP skin fittings with straight thread BSP ball valves screwed directly onto them. If what you say is true, and it all sounds right to me, then they are missing jam nuts?



Hard to credit how that would get past the collective engineering knowledge of all the European makers plus the Germanischer Lloyd/Norsk certification bodies, which certify many European boats.


A puzzle.

[Q Xopa]

Originally Posted by Dockhead

Makes perfect sense; thanks.


So it looks like we're missing jam nuts? I've never seen a jam nut on a skin fitting/ball valve connection. European boats without any exception (except perhaps the retro Rustler yachts which I believe have Blake's tapered cone sea cocks) have straight thread BSP skin fittings with straight thread BSP ball valves screwed directly onto them. If what you say is true, and it all sounds right to me, then they are missing jam nuts?



Hard to credit how that would get past the collective engineering knowledge of all the European makers plus the Germanischer Lloyd/Norsk certification bodies, which certify many European boats.


A puzzle.

This is correct. The straight threaded thru hull way of it being done, successfully for the most part, is strickly speaking not the best or standard way of sealing pipe unions.

As some here said, not much pressure involved so shouldnt be too hard to get em to seal.

As mentioned a straight threaded pipe fitting will commonly have a 'jam' nut. In the aviation trade I've heard the referred to as 'B' nuts.

Anyway to add to the previous mention of them there is usually a recess machined into one side of the nut where an O ring can fit.

There is also a smooth unthreaded section of the fitting that ends up corresponding with the nut recess so the O ring ends up sightly compressed sealing on the fitting and the bulkhead/ skin surface.

This is how 3,000psi fittings are commonly done so a bit in excess of whats needed for a thru hull. But seeing it was mentioned.

I guess you could emulate these concepts with a bit of lathe time on thru hulls if you wanted the absoulte last word in engineering practices.

O rings are great for maintenance. Cheap effective and easy to replace.

I have gone the Groco bronze adapter fittings, and minimizing the number of below water thru hulls route. I went from 14, when I got the boat to 3, 2 intakes and a transducer. The 2 intakes feed my Sea chest. I kept 2 incase one gets blocked. Teed to valves and 2 internal Sea strainer baskets. 2 easy to reach Seacocks and the boat is sealed. I also have straight stand pipes coming off the Seacocks that I can stick a broom handle length down to knock out the critters.

[Wotname]

Originally Posted by Dockhead

Makes perfect sense; thanks.


So it looks like we're missing jam nuts? I've never seen a jam nut on a skin fitting/ball valve connection. European boats without any exception (except perhaps the retro Rustler yachts which I believe have Blake's tapered cone sea cocks) have straight thread BSP skin fittings with straight thread BSP ball valves screwed directly onto them. If what you say is true, and it all sounds right to me, then they are missing jam nuts?



Hard to credit how that would get past the collective engineering knowledge of all the European makers plus the Germanischer Lloyd/Norsk certification bodies, which certify many European boats.


A puzzle.

Are you sure they are all parallel threads?

Many Aussie BSP male threads are actually BSPT rather than BSPP.

But yes, if they are are all BSPP, then a back nut should be included!

A bit (but not much) more info here https://en.wikipedia.org/wiki/British_Standard_Pipe

[Dockhead]

Originally Posted by Wotname

Are you sure they are all parallel threads?

Many Aussie BSP male threads are actually BSPT rather than BSPP.

But yes, if they are are all BSPP, then a back nut should be included!

A bit (but not much) more info here https://en.wikipedia.org/wiki/British_Standard_Pipe

Bingo.



Looks like I (and a lot of other people) have been confused about the threads on our fittings.


Maestrini, who made all my underwater fittings, have good technical literature on their website. Maestrini - Know-How, progettazione e caratteristiche tecnico costruttive, materiali, filettature



So as it turns out, all these fittings are threaded according to UNI EN 10226-1, which is TAPERED external threads, straight internal ones, made to be fitted together.


10226-1-2004.pdf

[mvweebles]

Originally Posted by er9

Yeah I agree that's why the one of the only two ball valves on my boat is getting replaced with this lovely beast. The raw water intake will get the new groco because I dont think I can fit even a 3/4 spartan in there.

Cool! An old tapered seacock style. I didn't realize these were still available.
https://www.spartanmarine.com/all-pr...artan-seacocks

These have an indefinite service life but are relatively high maintenance to prevent weeping (confession: this type of maintenance rarely percolates to top of my to-do list so this is not a good choice for me). The drain plug on the body can be replaced with a grease zerk for lubrication, though zerk should not be left in place as most are plain steel. Like the Groco BV series seacock (which comes with a zerk), it is UL Marine and is field serviceable by blocking water inflow on the mushroom thru hull similar to the adapter plate. The tapered style shown is pretty easy to service as the attached hose does not require removal. Spare parts is a tube of lapping compound. They are 100% bronze. There's a case to be made for these old school seacocks....if you're willing to sign up for the enhanced maintenance. Would also make sure they are installed in an area where service access is manageable.

Back to the thread. I understand the case for the adapter plate. I learned something which I often do from this forum. But I am not convinced it's the right choice for me vs the full Groco BV. A ball valve on the adapter plate would be easier to service than the Groco BV, but not by much. Both would require a large wrench. To rebuild, the BV requires carrying some seals whereas the ball valve requires a full replacement which should be carried in spares as I'd be surprised if UL Marine valves are widely available worldwide, though cheap brass ones are and would last a while. I have to observe that catastrophic failure of a thru hull is extremely rare so its incredibly unlikely that a cruiser would find themselves in a gotta-have-it-today situation. It's a question of whether you're more comfortable rebuilding (BV) or replacing (adapter plate). Having a grease zerk on the valve is a benefit and a distinct nod to the BV unless there are ball valves similarly equipped.

But I now understand the case for the adapter plate. Not the right choice for me but for folks with an NPT ball valve connected directly to the straight thread mushroom thru hull, a practice that is all too common, the adapter plate (or integral seacock such as a Groco BV) is a no-brainer. Never mind that it is not field serviceable because requires a wrench on the outside, the valve-on-mushroom arrangement is often horribly exposed to lateral force and is a catastrophy waiting to happen. Anything you do to strengthen this arrangement is a huge plus.

Thanks for educating me!

Peter

[sanibel sailor]

A few thoughts.

A standard valve can be replaced with the boat in the water. It is ugly, lets a bit of water in the boat but is doable. I was in a bad pinch and did it thru necessity due to a terrible prior install. Leaking steel elbow on a valve where the elbow was prevented from being rotated out for removal by an obstruction. POS plastic valve precluded trying to force it. Properly installed, can anyone envision a need to replace a valve so urgently that it cannot wait until the next haul out? The need to replace one in far off anchorage suggests carrying spares. Does anyone?

Zerks are available in stainless, brass, plastic, etc. In a huge variety of threads including SAE, metric, NPT and BSP.
https://www.mcmaster.com/zerk
If I recall on my old Cape Dory, with Spartan tapered cone seacocks, the machine screw was 12-24 which is a PITA to deal with.

A strainer was mentioned. Seemed like a good idea to me at one time. I tried one once and removed it at the next haul out. Its main function seemed to be blocking me from getting at the barnacles inside the thruhull.

[s/v Jedi]

These are the right valves to go on the flanged adapter plates. Grease fitting, full flow etc. https://www.defender.com/product.jsp?id=3353671

[Wotname]

Originally Posted by Dockhead

Bingo.



Looks like I (and a lot of other people) have been confused about the threads on our fittings.


Maestrini, who made all my underwater fittings, have good technical literature on their website. Maestrini - Know-How, progettazione e caratteristiche tecnico costruttive, materiali, filettature



So as it turns out, all these fittings are threaded according to UNI EN 10226-1, which is TAPERED external threads, straight internal ones, made to be fitted together.


Attachment 219183

The whole world (almost ) spins on BSP .

[mvweebles]

Originally Posted by s/v Jedi

These are the right valves to go on the flanged adapter plates. Grease fitting, full flow etc. https://www.defender.com/product.jsp?id=3353671

100% agree. UL Marine Listed and I see they have a zerk fitting too. I believe they are rebuildable in place too and likely take same parts as the BV seacock do. At around $100 for a 1-1/2" valve, some may consider it expensive. Considering the importance, a good place to spend the extra dough. But cost may drive towards rebuild vs replace. Combined valve and adapter is about 30% less expensive than similar sized BV seacock and would have similar attributes. Adapter /valve combo is not as compact. That's about it.

Peter

[Dockhead]

Originally Posted by mvweebles

. . .At around $100 for a 1-1/2" valve, some may consider it expensive. . .

I don't think you can find quality ball valves for less than that. I paid something like £200 each for my 2" Maestrini ball valves. Don't remember what the 1 1/2 ones were, but a lot more than $100.

The Groco fittings are made of real 95 85-5-5-5 bronze (otherwise known as "leaded red brass"), which is the best material for underwater fittings. Accept nothing less!

The only thing I don't like about them are the brass balls and shafts. But I don't think there is any point to rebuilding something which costs only $100 anyway, so I guess it doesn't matter. I guess those will be good for 15-20 years, at which point I think it makes sense to renew them, then go another 15-20 years without worrying about it. I think at $100 that's an excellent bargain



Maestrini used to use brass balls, but they have now gone to either bronze balls, or plastic, with bronze shafts . The brass balls were the only thing I ever had trouble with -- occasionally the chrome flakes off of them.

[a64pilot]

Maybe 85-5-5-5 ?

[Dockhead]

Originally Posted by a64pilot

Maybe 85-5-5-5 ?

Yes, of course. Typo!