I'm trying to change out a leaky spray attachment on my kitchen sink. The nut that holds the hose in place is up behind the underside of the sink. There isn't enough room to get a pair of pliers or a wrench in there to turn the nut. Is there a tool for this? How do I get it loose without taking the sink out of the counter?

Yes, it is called Basin Wrench. Home Depot sells it for few bucks.

Just propping up milo's answer.

You can sometimes buy the wrench head alone to fit on a long socket extension arm (if you have one) or buy the whole set as shown in the picture.

It's the Tool for that job.

In Addition: They sell 2 or 3 sizes of Basin Wrenches. Get the one that has smallest "claw" . It will grab small nut much easier...

Another Option if it isn't too late.
If the problem is with the sprayer and not the hose. Replace the spray head. Unscrew collar on spray head. Remove small wire clip in shape of a C, slide off head and replace with new one . The new head should come with new clip. Keep track of order of washer positions. The model of faucet should be on the base of faucet arm ( might need microscope):p
They do make a universal replacement spray head ( fits every model but yours) :rolleyes:
hawk_eye