The Test Bench
For a long while I have been meaning to test the strength of a ball valve threaded directly onto a thru-hull as many production builders do for seacock installations. These same builders very often display the ABYC logo proudly suggesting their vessels are built to meet the safety standards. In all fairness to the builders I suspect they believe these installations do or would meet the minimum safety standards but as I found out they certainly may not. We can't blame the builders for installing UL Marine parts and then not having them meet the minimum standards. You would assume the manufacturers would have tested these fittings for the application into which they are sold..
As I just found out the 3/4" Marine UL rated bronze valve threaded to a 3/4" Marine UL rated thru-hull fitting I purchased, does not meet ABYC H-27 Standards. It failed at just 404 pounds and I was an 1 3/8" below the "innermost" hard piping so had slightly less leverage than I would have had I been able to apply the load at the absolute innermost "hard piping". This 3/4" installation should have easily handled 500 pounds for 30 seconds if it were to meet the ABYC H-27 standard.
Does this test mean it will fail in normal use? Probably not, but we had one fail on us when a spare alternator slid across a shelf and hit the in-board end of the assembly so it can/could potentially happen.
My point here is that when buying a boat with this type of installation please be aware of and know that it is, and can be, a potential week point that may not meet the minimum ABYC safety standards for seacocks and thru-hull fittings, at least in the 3/4" size range..
What do the ABYC definitions mean?
27.4.4 Seacock - A type of valve used to control intake or discharge of water through the hull. It is operated by a lever type handle usually operating through a 90° arc, giving a clear indication of whether it is open or shut, and is typically of the two following types:
188.8.131.52 Flanged Sea Valve – A Seacock with an integral flange used to individually and securely mount the device directly to the boat hull structure.
184.108.40.206 In Line Ball Valve – A Seacock designed to be supported entirely by the through-hull fitting.
Some key points of ABYC H-27:
27.5.1 All piping, tubing, or hose lines penetrating the hull below the maximum heeled waterline, shall be equipped with a seacock to stop the admission of water in the event of failure of pipes, tubing, or hose.
27.5.4 Seacocks shall be designed and constructed to meet ANSI/UL 1121, Marine Through-Hull Fittings and Sea-Valves.
27.5.5 Thru-hull fittings shall be designed and constructed to meet ANSI/UL 1121, Marine Through-Hull Fittings and Sea-Valves.
27.6.1 A seacock shall be securely mounted so that the assembly will withstand a 500 pound (227 Kg) static force applied for 30 seconds to the inboard end of the assembly, without the assembly failing to stop the ingress of water.
220.127.116.11 The installation shall prevent any movement of the assembly.
18.104.22.168 Threads used in seacock installations shall be compatible (eg. NPT to NPT, NPS to NPS).
The above comes from ABYC H-27
So How Did It Do?
Not real well.
Rather than trying to describe the failure with photos I made a video, that is unedited, to show the failure.
CLICK THE LINK BELOW TO SEE THE VIDEO:
The thru-hull failed at 404 pounds while trying to get to the 500 pounds and let it hold for 30 seconds. It never even made it to the ABYC minimum, let alone held it for 30 seconds..
The test was performed in my shop using the work bench as the test jig. I was planning to rig up some 5/8" thick fiberglass and bolting it to the bench using some big backing plates. After running some numbers it appeared the 3/4" plywood should handle the loads.
I used a calibrated digital load cell to measure the load being gradually applied to the seacock. The load was measured in pounds and set to capture the moment of failure or "peak hold". To apply the load I used an old Lewmar self tailing winch attached to the end of the work bench.
The thru-hull was fitted to my bench and tightened down well using a spud wrench. The valve was then threaded onto it and the elbow threaded into the valve. I was able to get 4 full turns on the valve to thru-hull.
The ball valve to thru-hull is a known thread mismatch, NPS to NPT, but this is what is very often done by builders, boat yards and DIY's. I wanted to mimic a "real world" type installation and most, at least in bronze, are of mixed parts, not just one brand. It was not the thread mismatch that failed.
This image shows a close up of the failure. It's not a surprise that it failed where it did.
The materials for this test were all "off the shelf" and purchased from Hamilton Marine in Portland, ME.
To mimic what a boat owner or yard may install the materials were a mix of what was on hand at the chandlery. The bronze UL Marine thru-hull fitting was made by Apollo/Conbraco, the UL Marine valve by Groco and the bronze elbow was also manufactured by Groco.
Where The Load Was Applied
If you look at the video you'll see where the "load" was applied to the elbow which is a full 1 3/8" inward of where the ABYC load is to be applied at the "innermost" portion of the assembly. Here I am measuring the load contact point from the "innermost" portion of the assembly.
I just don't have a good way to apply the load to the "innermost" portion of a male hose adapter so used an elbow instead. In the process I gave up 1 3/8" of "lever" which actually favors the seacock when testing to ABYC H-27 standards. Despite this 1 3/8" of favorable advantage for the seacock assembly, the thru-hull still failed at 404 pounds and never got close to 500 pounds for 30 seconds.
A straight male hose adapter is even taller than the elbow and would thus provide for more lever and move "innermost" even further away from the hull.
The Inboard End
On the inboard end there was just 7/8" of exposed thru-hull which, as I previously mentioned, mimics the installations I see on a daily basis. When I see a valve on a thru-hull I rarely if ever see them cut shorter. It would certainly help to make the assembly shorter but I just don't see it done very often in the real world.
Even if I managed to get the valve within 1/8" of the thru-hull nut, and then moved the load to the proper positioning for ABYC H-27, the thru-hull would have still failed at well below the standard of 500 pounds at the innermost position of the assembly for 30 seconds..
This Is A 2011 Production Sailboat
Keeping the assembly closer to the hull would definitely help and limit the "lever" that could be applied to the thru-hull, but, a flanged seacock would be significantly stronger and should meet the 500 pound standard even using "typical" adapters etc..
How about this builder..... Someone paid over $200k for this boat! Is this type of installation worthy of $200,000.00 ? I'll let you be the judge...
Cut It Shorter?
As I mentioned they are rarely if ever made shorter. Cutting them shorter would reduce the lever arm but negate any thread match if a "combination threaded" thru-hull was used. A real Catch 22.
Please click on this photo and ask yourself how one might actually get to the thru-hull nut if you needed to? I can tell your it will be tough with the hull liner surrounding it. Just an honest question....
The Only Reason.....
The builders get away with installations like this because we the buyers allow it.
If you want better construction techniques keeping your family afloat it needs to start with us the customers!
This was another 2011 brand new six figure vessel.
Some builders do spend the time to make their vessels robust. This was also a 2011 production sailboat. She has been fitted with flanged seacocks and utilized solid fiberglass backing plates.
If I was paying six figures for a vessel I would expect well fitted, robust below water seacoks in either Marelon or bronze.
Food for thought....
A Proper Installation For Bronze
This was a nicely executed installation on a new Island Packet. They even used solid fiberglass backing blocks..