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Old 05-12-2012, 05:17   #121
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Re: Brass Seacocks -

Quote:
Originally Posted by Bill_E View Post
I managed to find the DIN standard. Itís actually DIN 3357-4 for nonferrous ball valves. It turns out that in the sizes of interest to me, there are three possible threads, including NPT. I will just have to get some pipe and see if itíll thread easily into the ball valve in place. I hope itís NPT because Iím going to have a hell of a time finding the others.

Regarding wall thickness, Thanks to MaineSail!! I understand that when you cut the thread you reduce the wall thickness of the starting pipe. I suppose that when buying thruhulls one should look for those with a ďthickĒ wall and suffer the loss in ID. Better to have some flow restriction than a weak system.

Now, what is the downside to using an NPS tap and cutting the thread in the ball valve to match the NPS thruhull? It doesnít seem that this would drastically reduce the wall thickness because the ball valves already have pretty thick walls. I guess this falls into the category of ďgood enoughĒ until I haul out and redo everything according the best practices.


Bill
The first couple of threads in the ball valve are the same size as the parallel thread, by running a parallel blind or plug tap all you are doing is making the thread the same size.

It is a common thing to do, a parallel thread is far better of holding pressure than a tapered one hence hydraulic's etc prefer. Compound like Loctite Pipe sealant is the go!

A properly made/cast thru hull will have maximum thickness so as to not be an issue.
Remembering a caulked boat relies on putty and cotton so what you are doing here is not a weakness :-) (a joke before the boat police comment).

Cheers
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Old 05-12-2012, 08:37   #122
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Quote:
Originally Posted by goboatingnow

BSP parallel and taper threads are designed to go together and regularly do in all forms of plumbing , The tapered thread is designed to provide the sealing unlike parallel thread joints where some other sealing is required.
I'm not a plumber and you may be, but I have always heard the opposite. Tapered threads are for joining and sealing and straight threads are only for joining.
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Old 05-12-2012, 08:41   #123
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Re: Brass Seacocks -

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Originally Posted by PamlicoTraveler View Post
I'm not a plumber and you may be, but I have always heard the opposite. Tapered threads are for joining and sealing and straight threads are only for joining.
Plumbing and boats are different trades, i'm a boat builder and my position is a parallel thread matching a parallel thread with sealant is the optimum solution short of a flange other wise you will bind on the threads and that will be the the extent of the seal..... Not on my watch!
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