How can I unscrew the faucet nuts in the tight space behind my sink basin?

Question

My bathroom faucet is dripping, and I would like to change the washers in it. The problem I am running into is the placement of the nuts holding the faucet valves in place:

This is the underside of the sink, the hot and cold valves are on either side. The nuts holding the valves in are quite large, and they are inside a small recessed space that I can barely fit a small pliers into, much less one large enough to actually get around those nuts. Does anyone have any suggestions for how I might get those nuts off?

Update: Always make sure you are asking the right question first, see answer below. Though if anyone is in a similar situation to mine and actually needs to remove a valve, some of the other suggestions here look helpful.

Answer 1

This is exactly the purpose of a basin wrench

Here's a picture from familyhandyman.com that shows a basin wrench in action:

Note that as mentioned in another answer, you usually don't need to remove the faucet to replace the washers; but if you do need to remove the faucet for whatever reason - this is the tool.

Answer 2

Maybe I'm missing something here but why are you trying to take off those nuts? The washers for the valves are topside. You just have to remove the valve stems to expose and change the washers. If you wanted to replace the faucet, then you'd need to get these nuts off.

Answer 3

I usually remove both of the supply pipes then make a socket to fit from a suitable sized metal pipe.

Even found a copper pipe hammered on was sufficient in some cases.

Answer 4

A crowfoot wrench might do it, if you can find one that's the right size to fit those nuts.

Another option (much more work) is to disconnect the pipes lower down (where they join the hard lines), disconnect the drain, and pull up the whole sink.