Saddle valves, also called pin or self-piercing valves, are for low volume water flow, like humidifiers or ice makers, and are fast, cheap, easy.
You install a saddle valve by attaching a clamp onto a water pipe, then tightening down a pin valve until it pierces the copper pipe. There is no cutting, soldering, or special tools. Simple. The problem is they can leak. Most don’t, but once installed, touch them as little as possible.
If the valve has a slight leakage around the valve stem, simply tightening the packing nut may stop it. If it won’t tighten, or the valve handle doesn’t turn, or the valve has corrosion around the stem from past seepage, then just replace it.
Replacing your saddle valve
First, turn off the water and disconnect any tubing. You can drain the pipe, but the hole is so small that leaking is minimal. Then place the needle point over the pin-hole hole made by the previous valve and tighten each clamp bolt a little at a time so the pin tightens evenly. Finally, test that the valve works and there is no leakage.
Don’t over tighten the bolts because copper pipe can be crushed.