The water shut off valve that is under my sink in the bathroom is leaking and I need to replace it. I am wondering if I need soder the new one or can I just put some thread tape around it.
TURN THE STOPCOCK OFF OUTSIDE ..DRAIN WATER OUT OF THE TAP AND REPLACE WITH NEW ..
you solder it, because your pipes have to be copper, which never have threads, so the threads tape would be useless right? just ask a plumber to come over and do it and watch them, really good way to learn without paying a college degree.
If it's a compression style valve, try tightening the nut some more to get it to stop leaking. If it's a screw-on, then yes, remove it and add more teflon tape-clockwise around the threads. If it's leaking around the stem, then all you might need to do it to tighten the packing nut a little-that's the nut directly behind the handle.
You could shut off either one. Find the valve on the water heater inlet and shut it off or find the water meter to your house, usually near the street and turn off the valve. You can probably use the same wrench that you intend to use to replace the leaking angle stop under your sink.
More ofter than not the innards of a valve will deteriorate and start to leak, when that happens its best to replace the valve. Since you ask about soldering the shut off valve, I'm going to assume that you have a copper line coming out of the wall. Older valves required soldering, nowadays there is a compression fitting that eliminates the need for soldering. Once you have the correct size of the pipe turn off the main water supply. Remove the old valve (may need to take a hacksaw or tubing cutter, if its soldered on). Then slip the new nut and compression ring over the pipe. Next bring the valve up to the pipe and tighten the nut to the valve. Once the valve is secured on attach your lines, preferably new replaced lines. Open the valve line, and then turn on the main water line and check for leaks.
