New Fangled Hoses & SEACOCKS!

[ebb]

Safe to guess that seaacock sits on a tall 'backing plate' (Mound) so that the thruhull can be fully screwed into the seacock as the last step in installation. Kind of backwards from what you'ld expect. The seacock is mounted dry with the thruhull, the seacock is 'wet' mounted first, yours was probably glued in with 5200, hopefully polysulfide, left to set. Then the thruhull was screwed in as the last thing, hopefully with polysulfide. personally I would screw it in with lanoline or Dolphinite.

Thru hulls have a backing nut, which gets discarded when a seacock is installed on it. It couldn't have a nut if it had a tapered thread.

With enough rubber caulking the thruhull could fall out befor the hull would leak there, because the seacock completely covers it. And usually is screwed or bolted to the backing. The seacock has to have a female taper thread on top because that's where the plumbing begins.

Inline ball valves are exactly that, aren't they? They have no base. In line ball valves have tapered threads BOTH sides. Therefore you can't screw them down very far befor they start tightening up.

IMCO no one making inline ball valves makes a thru hull for them. Because they never were suppose to be used for under water inlets. Not only do they sit on top of the thru hull but they are not screwed very far on. And as I think Scott's photo of threads shows. you can see galling there where the mismatch has bent the threads. Tapered male to tapered female (if they are the same size) fit like socket.

I notice that Triton Tim uses inline ball cocks for above the static waterline plumbing exits. Also he has used premoulded auto hose for his cockpit drains, last I read. The reason is the tortured impossibility of bending short straight hose to compound curves. He writes a forthright description of his adventures under the cockpit - and in the lazarette.

Ron Basey in a How-To mentions nothing on the NPT, NPS anomally that Scott extracted from the marine plumbing morass. Thanks Scott.

As to Good Old Boat's two pager on "Inspecting and maintaining seacocks 101" - the drawings are great. It's ok for guys puffing on their kaywoodies with the cuffs of their white shirts turned up looking for their tapered plugs.
But as we know, there's a lot more to the understanding of saltwater seacock. I hope, without much faith, that seacocks 102 comes along that will show how to install the things, how to pull maintenance, what to look for in a questionable installation. 103 might go further into seacock design, how to recognize if your chrome balls are flaking or your stainless stell one has crevis cracking, etccc.

[ebb]

First this:

"And then again, when you sit at the helm of your little ship on a clear night and gaze at the countless stars overhead, and realize that you are quite alone on the great wide sea, it is apt to occur to you that in the general scheme of things you are merely an insignificant speck on the surface of the ocean, and are not nearly so important or as self-sufficient as you thought you were. Which is an exceedingly wholesome thought, and one that may effect a permanent change in your deportment that will be greatly appreciated by your friends." James S. Pitkin

This was inserted into the discussion on the above subject by some wag on

http://www.boating-forum.com/cruisin...ks_169243.html
http://www.boating-forum.com/cruisin...on_168351.html

(hope that's right!)
Their discussion mirrors ours, and is well worth a visit by anyone of us. Very good exchanges on serious business.

(ok, it doesn't come up,

I refound it by using google this way:
type in: seacocks www.boating forum
find Through-hull and Seacocks (about three down)
hit and light up "More results from www.boating-forum.com
Hitting these light ups here won't work. Have to do it thru google!!!

Hope it works. Edjikational. Worth the visit. Guys just like us. Only shorter winded.

[Scott Galloway]

Hmmmm,

Ebb,

Those links didn't link for me.

Bill,

Your hose bib tail fitting issue is most curious. I don't know very much about pipe threads, but I know more than I did a couple of weeks ago.

From the information that I have gathered, I am under the impression that straight threads have their best application whenever mechanical strength is important.

As an example, straight NPS "M" threads are used in scaffolding that is quickly assembled and disassembled at construction sites. A watertight joint is not even an issue I construction scaffolding, but the joint being able to withstand significant lateral force is a big issue, as you might imagine. The joint gains its strength by the many many turns of the straight threaded male end inside the straight threaded female end.

Another application for (NPS) straight threads is on thru-hull fittings and the matching straight threads on bottom end of sea cocks. This is very important, I suppose, because if a strong lateral or other force were to break a pipe below a sea cock valve, the result would be catastrophic, and even more so if the break is ragged. So, straight threads on a thru-hull fitting mean that female threads inside of the bottom opening of the sea cock will spin round and round again down on the male thru-hull shaft until the sea cock is tightened down like a great big lock nut against the top of the backing plate, and the thru-hull flange is pulled up very tight against the hull. To accomplish this, the shaft on the thru-hull may have to be shortened somewhat of course by cutting it off.

This whole unit would probably leak of not bedded properly, because these are straight threads, but you have bedded the thru-hull flange, the joint between the inside of the hull and the bottom of the backing plate, and the space between the top of the backing plate and the bottom of the sea cock with a marine sealant. The compression created by tightening the sea cock down on the backing plate holds the unit together and maintains compression in what is a very complex joint consisting of sea cock, backing plate, thru-hull threads, external thru-hull flange, and marine sealant.

Now, if instead of a sea cock you use the in-line ball valve option like the one on your sink drain pictured above, the female lock nut can spin all the way down the male thru-hull shaft to the backing plate and tighten nicely against it, which means that the thru-hull flange will simultaneously be pulled up tight against the outside of the hull.

So when comparing a sea cock in the first case to a lock nut in the second case, the two are basically the same functionally in that the lock nut has straight threads and is essentially operating mechanically in the same way that a sea cock operates, but of course a lock not has no valve in it, and here is where the problem arises:

You have to deal with the open end of that thru-hull shaft. You want a shut-off valve, but you decide to be modern and forsake the traditional sea cock with its NPS threads bottom and ample mounting flange. So you select an in-line ball valve instead. Now my understanding of these in-line ball valves is that they have tapered (NPT) fittings on both ends, so you might find that your tapered NPT threaded ball vale will be incompatible with the straight NPS threads on the thru-hull shaft, or you might have a case where you do get the requisite number of turns recommended by the ABYC because your supplier thought about this somewhat, and used a non-standard (bastard) straight thread on his thru-hull to allow the female NPT tapered ball valve threads to slide down further in those bastard threads.

I was told by a supplier that the ABYC wants 3.5 turns by hand before the joint is mechanically tightened, but I haven’t read that anywhere. I did read in another place that the joint must be able to withstand 500 lbs of force over 30 continuous seconds without breaking. We have also read on this thread that Commander Pete was successful in breaking a couple of thru-hulls with these in-line ball valve installations by simply trying to remove them, and that they both broke in raggedly and not in a nice straight break below the valves.

I have been told by my yard and my surveyor that these installations are acceptable and done by most yards.

It is as of yet unclear why my brand-new system failed the second time in a week. We will know more when we get the parts out next week.

Now finally, once you are inside the hull and beyond the valve, all fittings that you are likely to encounter, including the top fitting on a traditional sea cock, wil have tapered (NPT) threads, because you not longer have a dual compression feature like that offered by a sea cock or lock nut and thru hull flange pulling a joint together with lots of goop in between.

So, once we are at the top end of the sea cock, or at either end of an in-line ball valve, we have entered the world of conventional plumbing with tapered threads offering their version for compression (which is created by the tapered threads coming together), and this makes for “generally” leak proof joints.

So having said all of that about a topic that I know very little about, I find it interesting that either your hose bib tail or in-line valve has straight threads while the other has tapered threads. The threads on the top of the sea cock, the threads on the top of the ball valve and the treads on the bottom of the hose bib tail should all be tapered threads, I would think.

Of course there are some people who will attach hose bib fitting with a female end directly to a thru hull shaft with no valve in between, and this is commonly done for above water through hulls as you know, so perhaps they make hose bib tail with straight threads as well as with tapered threads, but my understanding is that the top opening of both a sea cock and both ends of an in-line style ball valve would have be tapered NPT threads.

I am interested in how your sink drain ball valve to hose bib connection issue is resolved. Keep in mind that this sonnection is above the valve. The connection between the ball valve and the thru-hull is ven more of a concern.

[ebb]

Scott.
read the end of post #29 - follow instructions to the letter.

As post #28 intimates: THERE ARE NO THRUHULLS FOR INLINE BALL VALVES.
[ further research refutes this, at least for Marelon]

So you have to use the backing nut of the thru hull with suitable rubber compoubd to weld the fitting in place. Then you have to turn the NPT valve on to the NPS, which very soon stops turning. If the idiot keeps turning he or she screws up the threads on the thruhull fitting. And the glued in thruhull will start turning, And can possibly crack the threaded tube because it is thin and compromised by the very threads that make it a fitting. Remember, it is a fitting designed for a seacock. It is not designed to take a load.

Pipes and fittings come is thicknesses too. Schedule 20, 40, 80, 160 - same outside diameter but bigger number thicker wall. You might look for thicker wall thruhulls, if you will persist on screwing an inline valve on to your Schedule 20 thru hull fitting


It is possible that some manufacturer by now has a thru hull with NPT on top and a locking nut on NPS threads on the bottom. I don't know. It would be a no brainer to produce. NOW, if such an item does not exist, we have to assume some regulatory agency says they can't. If they can't then boat builders are installing inline valves illegally as seacocks, so is your yard manager, and your surveyor should go back to house painting. He's dead wrong too.

In a properly installed seacock, as specified above earlier post no b.s., The thru hull fitting can be said to FLOAT inside the seacock. There are NO loads on the fitting. There is NO backing nut on the thruhull when the seacock is there. You cannot compare the two installations, they are apples and oranges.

The seacock is installed first with the flange either lagged onto the backing block or thru bolted thru the hull.* The thruhull is then screwed into the unit and seated onto the hull if mushroom - or into the hull if flush. One merely screws the fitting in dry and out again for shortening until it fits perfectly. This is how it has been done for decades. NO strength is imparted to the seacock installation by the thruhull.


*If that mound under Bill's seacock is epoxy-chopped strand-cabosil mix and permanently affixed ie molded to the hull and if the seacock is glued on there with polysulfide or 5200, then IMCO it is good enough to screw some lags into the backing thru the designated holes - bolts being unnecessary.

Thank you.

[Scott Galloway]

I am not sure that I would use 3M 5200 to bed a seacock, You would have one heck of a time removing it later. Also, 5200 is a slow cure so unless you will be out of the water for an extend time, I am told that 5200 is not a good choice for below water applications. If you feel differently, I'd be interested in knowing your perspective. Perhaps 3M 4200 (fast cure) might be a better choice if you don't want to use polysuylfide.

Sorry if my last post gave the impression that I was trying to explain how to install a seacock. I was not. Indeed, I have never installed one. What I was endeavoring to do was to give one view of the dynamics of what might be happening inside a seacock to thru-hull joint as compared to what might be happening inside an in-line ball valve to thru-hull joint.

Here are a few photos that might help. The first two are from Groco's webpage and show the thread locations and types of threads for both seacocks and in-line valves, and also the mounting configurations.

[Scott Galloway]

Groco states,

"Groco does not recommend the use of in-line valves as seacocks for these reasons:

1. In line valves have no means of attachment tot he vessel hull or backing block...

2. if the connected thru-hull fitting become damaged or broken.... there would be no way to shut off the flow of water into the vessel.

3. In-line valves have NPT threads, which are not compatible with the NPS threaded thru-hull fittinmg (unless the thru-hull fitting is machined with 'Combination Thread'. Installing an in-line valve onto a thru-hull fitting will create a mismatch of threads resulting in minimal thread engagement between valve and fitting, and an unsafe installation. property damage and personal injury could occur. If you choose to install an in-line valve as seacock the thru-hull fitting ue dmust have 'Combination Thread.' "

Here is their in-line valve-as-seacock drawing: oops and
that didn't up-load, so I will continue with this series of photos at a later time.

[Scott Galloway]

Here is that drawing of the in-line valve installation: