My washing machine supply line is still leaking after I turn the handle to the off position! Why and how can I fix it? Any suggestions or advice would be greatly appreciated! Thanks in advance folks!
Some dripping can be expected but it has to stop at some point, if it doesn't that's your sign that the valve is defective.
If your hoses are leaking, replace them. They are inexpensive.
With the valve off, turn on the washing machine to the fill cycle, warm water temp. That will relieve pressure in the lines. Turn the machine off. If the hoses repressurize and leak, your shutoff valve is faulty.
In a lot of older homes, these valves are much the same as the outdoor faucets and can be re-washered and repacked similarly. If you have a machine hooked up and there are no leaks, this can be ignored. Often you discover this only when the old machine comes out, leaving the valve free to leak. If it's not severe and you're going to just replace the machine than simply run a hose between both valves till you get the new machine in, then mop up after it's hooked up. Do not leave the hose in place 'permanently' as a fix because it is tying the hot into the cold which can lead to someone turning on cold and getting burned from the unexpected mixed hot. Newer style shutoff valves may have to be replaced if parts aren't available for a rebuild (I've never tried that, I always just put in new valves to be done with it).
Shutoffs that don't shut off are only a problem when you need them to perform their job and they don't. They had better work if a supply hose or line fails or you will have to shut down the whole house the stop the flooding, and most folks aren't ready for that.
I have an old Folgers coffee can, you know the big can, full of all kinds of washers. But every time I have to fix a leak, I replace the angle stop/faucet. Why? it saves me time and I know it won't leak. Washers, they give my headaches.
I do the same on anything except a seldom-shut-off service valve. There's not any wear to be concerned with on them. More often than not, a bad washer means a bad seat chewed it up, and by the time you reface or replace the seat, it's just as easy to put in the whole dang thing. Since most DIY'ers aren't experienced with sweating copper pipes, a washer replacement makes sense here.