fitting thread question

[mikejurasw]

Hello!
Here's my question: I was helping a friend with a leaky shut-off valve in their basement (cold supply to upper floors). The house has a lot of age and my suspicion was that the packing was shot/gone. I took the valve out at the bonnet (couldn't get the handle off) and worked on it like that.

But...while I was working I noticed the partner hot-water shut-off had been capped, and I rummaged in the bag for parts just in case my re-packing didn't work. I found a 3/4 galvanized close nipple (I know: don't mix the metals; I was just checking) which was the proper diameter but the threads were less fine and wouldn't match up.

For my future reference, can a pro explain to me the difference I was seeing in the threads between the brass bonnet and the galvanized piece?

Much obliged!

MM

 

[Snoonyb]

There are several competing forces in the plumbing world, expansion and contraction as well as structure of the parts, where a fine threaded part with a 1/8th" surface is required to withstand the same resistance as a 3/8tth" coarse threaded part.

It's just the mechanics.

 

[mikejurasw]

Ok....so if I'm understanding, I could potentially shop for a "3/4 inch, fine-threaded male plug" for such an application?
(I'm familiar with "compression" threading being different that "FIP" threads, etc. , is that the same?)
I guess I'd like to know what you guys carry in your kit to band-aid something like this until you have time to properly replace the valves.
Thanks!

 

[Snoonyb]

Also, I neglected to mention that of the 2 brass products employed, red, is the most common, because yellow is softer and less resistant too corrosion.

I used to carry a couple of short pieces of 3 different hose dia., and hose clamps, and plugs made up.

 

[bud16415]

There are a variety of straight and taper pipe threads including USA and British standards and metrics. Then there are all kinds of tubing and connectors out there and oddball stuff like aerator threads and whatever the valve manufacture might have done internally in their product.



Unless you really live off the grid there is a building center or Ace Hardware within a few miles and I let them stock all the parts I may need. I have a few 8 quart baskets that over the years have collected leftover fittings and I will take a quick look to see if I have what I need. I do stock a selection of PEX fittings as I have redone my whole home with PEX. Other than that it is really quicker for me to figure out what I need when I need it at our local Ace.

 

[mikejurasw]

Thanks for the tips!