Most ice makers and whole house humidifiers I inspect have a saddle valve supplying the water. These are devices that allow for a very fast, cheap, do-it-yourself installation of a ¼” water supply line.
Saddle valves are installed by tightening a metal clamp on to a water pipe, then tightening down a needle valve until it pierces the water pipe. No cutting of pipes is required, no soldering, no special tools… simple. Very DIY. The needle just pokes a hole in the pipe, and I’ve heard it can be done without even turning off the water… not that I’ve ever tried. There has to be a catch, right?
There is. These saddle valves are prone to leakage, and they’re not allowed by the Minnesota State Plumbing Code.
Most of them don’t leak, but they have a much higher chance of leaking than a properly installed water valve. If they do end up leaking, the repair will involve doing all the stuff that you’re supposed to be able to avoid – cutting, fitting, reaming, cleaning, soldering, etc.
My advice is to not use saddle valves. If you plan to install an appliance that needs a ¼” water pipe, have a proper shutoff valve installed. It will take more time to do it right, but you’ll dramatically lower the chances of it leaking.
If you already have a saddle valve in your home, try to leave it alone. Every time you operate the valve, you increase the chances of creating a leak.