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Compass Marine How To | all galleries >> Welcome To >> Seacock & Thru-Hull Primer/Pre Information > Measuring the Overall Wall Thickness of a 1" Bronze Thru-Hull
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Measuring the Overall Wall Thickness of a 1" Bronze Thru-Hull

For this test I wanted to know the actual wall thickness of a 1" thru-hull fitting. The fitting is a standard bronze Apollo 1" thru-hull which I purchased right off the shelf at Hamilton Marine.

In this photo I am measuring the overall thickness of the thru-hull. It measured in at 2.99 millimeters thick.

I am illustrating this to show why simply sticking a valve onto a thru-hull (without flange) is not as strong or as safe as using proper flanged seacocks and threading the thru-hull into a flange or thru-hull. Simply threading a valve directly to a thru-hull, with no flange, increases the risk that the thru-hull could be snapped off.

I personally had this happen to me when a spare alternator hit my ball valve that was screwed directly to a thru-hull and cracked it. This is the number one reason I will now only use properly flanged seacocks and thread the thru-hull into it.

Nikon D200
1/60s f/4.0 at 24.0mm iso100 full exif

other sizes: small medium large auto
Tanzerlover 17-Nov-2009 11:16
I am replacing the through-hulls and valves in my Tanzer 22 and found these articles answered my questions on not only how to, but also why I should NOT shop Home Depot and "save" some money as suggested on several other sites. THANK YOU! I regularly sail with children aboard!
john cly 18-Dec-2008 14:17
Your measurement to show the thickness is not quite accurate. The thickness is in the 'undistrubed' portion at the bottom of the thread groove. the measurement you are depicting will be about 1/3 larger than if you measure at the bottom of the thread groove.