Originally Posted by Bill_E
I managed to find the DIN standard. It’s 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 it’ll thread easily into the ball valve in place. I hope it’s NPT because I’m 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 “thick” 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 doesn’t 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 “good enough” until I haul out and redo everything according the best practices.
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).