Washing machine shutoff valves 1/2" MIP and solder

[stillsteamn]

Hi, thanks for allowing me into the forum. My old washing machine valves are stuck wide open. They are old gate valves, shown in the picture. I want to replace them with these new 1/4-turn valves. On the old valves, is the threaded joint that I marked in red the water-tight seal? Or just for mechanically mounting these valves into the box? My house water supply pipes are 1/2" copper tubing. The replacement valves I found are 1/2" straight threads, not tapered. I now suspect these 1/2" straight threads are the correct threads but they are just to mechanically hold the valve into the box. I suspect I need to open up my drywall, cut the old copper tubing, and solder in these new valves. I already confirmed that 1/2" copper tubing fits nicely into the inside of the long threaded input side of these valves for soldering purposes.

Originally I was thinking the box must have 1/2" tapered threads for a water-tight seal of the valve to the box, but now I don't know. I might have to cut a hold in the drywall and take a peak, but your experienced comments will help.

If my old valves are soldered onto copper tubing, I could have really messed things up had I put a pipe wrench onto these old valves and started cranking.
Thanks!

 

[breplum]

Those replacements won't work unless you do the 'open the wall' work.
Don't forget, you can NOT screw FIP adapters on straight threads like that. You have to solder into them.
I recommend, just rebuilding the valves after turning the main off.
Rebuilding entails using waterproof plumber's lubricant and they should be fine.

 

[TomFOhio]

You should be able to take a pair of channel locks and back up the fitting that the valve screws into. Unscrew the valve out
and screw a new male hose bibb in.

 

[stillsteamn]

Thanks for the replies. The final solution was to use a backing wrench on the nipple and another wrench to unscrew the old valves and install new 1/4-turn ball valves (not the new valves shown in my original post!) These new valves are boiler drain valves with 1/2" male NPT threads on input side. I used plumbers tape and blue pipe thread sealant. These valves are what I could find locally. I saw some online made by Dahl that are intended for washing machines and have a nice 90-degree output angle instead of these valves which angle up about 10 degrees since they are intended to be used in a different application. But they work fine and the reinforced hoses I'm attaching are not going to sag or kink.

The valves screw onto a nipple which is locked into the box with nuts top and bottom, and then apparently the 1/2" copper water supply pipes are soldered at the bottom of the nipples. I did not open the wall to see that part.

Old valve is shown just to show what was removed.