Single handle Spray faucet leaks at it's base, leaking under the kitchen sink

make this steps and fix it. God bless you
f a faucet leaks, replace seals and gaskets . If a shower head leaks, create a better seal or replace seals .
If a sillcock wears out, replace the washers .
If a compression faucet drips from the spout, replace the washer and/or the seat .
If a faucet leaks from the handle, replace O-ring(s), replace the packing washer, tighten the packing nut, or replace worn packing, depending on the valve type.
If a ball or cartridge faucet leaks from the collar, replace worn O-rings .
If a disk faucet leaks around the base or has reduced flow, replace cracked or pitted disk assembly or worn inlet seals
If there is water under the sink, tighten the faucet-set locknuts under the sink. You also can replace putty or a gasket, replace a worn faucet, or replace leaky supply tubes .
If the aerator leaks around the edge, replace the washer in the aerator
If the spray hose leaks or has reduced flow, replace the O-ring on the diverter valve, replace a worn washer at the base of the spray head, or clean the diverter valve and spray head

make this steps and fix it. God bless you
f a faucet leaks, replace seals and gaskets . If a shower head leaks, create a better seal or replace seals
If a sillcock wears out, replace the washers
If a compression faucet drips from the spout, replace the washer and/or the seat
If a faucet leaks from the handle, replace O-ring(s), replace the packing washer, tighten the packing nut, or replace worn packing, depending on the valve type
If a ball or cartridge faucet leaks from the collar, replace worn O-rings
If a disk faucet leaks around the base or has reduced flow, replace cracked or pitted disk assembly or worn inlet seals
If there is water under the sink, tighten the faucet-set locknuts under the sink. You also can replace putty or a gasket, replace a worn faucet, or replace leaky supply tubes
If the aerator leaks around the edge, replace the washer in the aerator
If the spray hose leaks or has reduced flow, replace the O-ring on the diverter valve, replace a worn washer at the base of the spray head, or clean the diverter valve and spray head

This faucet has two O rings under the handle..Turn the water off at the valves under the sink, there is an allen wrench screw at the back of the handle. Loosen the allen screw, take the handle off. Then you will have to unscrew the faucet head from the base. (counter clockwise). Once the head is off you should see two O rings you will have to change them both. Also, inspect the O ring on the head itself. You should go ahead and change them all. Hope this works for you.

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.

turn off water remove handle and check retaining nut remove cartridge and check o-rings for damage or replace replace and tighten cartridge check for leak

check that nothing blocking hose return weight under sink

Remove spray head then faucet tighten connection on the spray hose

You have a bad internal o-ring or the sprayer o-ring is leaking, if you look under the sink turn it off and then turn it back on, if you see it leaking out the center shft where the water pipes go into then the faucet may have a broken pipe or loose pipe. check and tell me where it's leaking at. You can buy kits to repiar them they are inexpensive.

There are "o" rings in the area where it is leaking. You can get them at almost every hardware chain. Clean everything well with scotchbrite ant put silicon grease on before you put it back together.

Your problem is a simple one.

1. Turn off water to faucet.
2. Place a towel(s) in the base of the sink(s) to prevent any parts from going down drain.
   
3. Remove the handle to the faucet. (single handle only)
   
4. If not a single handle then remove spout from faucet.
5. If a single handle remove cap carefully and any loose parts.
6. Gently turn spout side to side while lifting to remove.
7. You will see a hole with a very small valve where the water comes out to the spout on the base of the faucet.

1. Remove this valve (which is a backflow preventer) and replace.
2. Reassemble and test.
   

Problem solved.