There's a rubber attachment for your garden hose available.
I'm not sure were you'd find it in the US but basically it looks like a long rubber bell.
You snap it onto your house and it seals around the plug hole and blast away.
It's brilliant and I've unclogged some nasty drains with it. No chemicals or acid needed.
Also... Be careful if you have a double sink because you'll spray water onto the ceiling above
