correct tightening torque for a noname single lever mixer tap
I'm not sure torque values are the right way to go about this since many things can affect a torque reading here. Most plumbers don't use torque wrenches. 

Instead, make sure all the seats and seals are clean and in good condition. It shouldn't take much torque to get a seal. It's not usually screw pressure that creates the seal, but o-rings that fit between the walls of parts, creating their own pressure, as well as internal springs.