Have a Blanco single-handle pull-out faucet with single-stream and spray option. Spray option can be turned on and off with a twist switch on top of the faucet. Our faucet is now stuck on spray option and will not switch back to single-stream. What can I do to fix it?

you can buy this wrench at a plumbing supply store

Clean out the aerator.

Check the hose connections at the spray head nozzle it sounds like it is leaking there and running down the hose and ending up under the sink.

You need to turn the water off under the sink. Disconnect the sprayer hose from the threaded shank under the center of the faucet body. Pull the spray head out of the faucet. Contact Blanco to receive your faucet parts free.

If you mean the top faucet handle, there is a small round plastic cap. You need to remove this and then remove the grub screw, handle will then pull off. Hope this is what you meant, if not post again. Thanks Paul.

The reason it is hard to turn from side to side is the top nut located under the lever is too tight and the the weight does go around the flex line that leads to the faucet but is only the to pull the sprayer back in place.

allen key is usually 1/8 inch

Turn your water supply off to the existing faucet.
With a crescent wrench and plyers remove the supply tubes from the shut off valves.
Unthread the sprayer hose that is attached to the brass connector under neath your faucet in the cabinet.
Unthread the lock nut and fastening plate which is on the same brass fitting as your spray hose.
Remove faucet from the sink.
Reinstall the new faucet in the reverse order.

Check fine filter at tip, probably blocked, got caught with same thing myself recently!!!

you can call or e-mail the company, if the faucet is the one in the picture it is a single cartdridge, turn of bith hot and cold water, take an allen wrench into the little plastic cover to remove the handle , unscrew the top cover or it might pop off, that there is either a large lock not or 3 screws holding down the cartdridge, take it out replace it put some faucet frease around all rubber gaskets then install it in the smae way it came out