Dripping tap

Could be the tap lever loose on the insert shaft.

You might want to check if the tap is still "quarter-turn" I've seen several examples of worn, slightly more than a "quarter-turn" taps. In these cases the real off-point is slightly before the lever meets the OFF end of travel.

PA

How have you tried to remove the cartridge? I usually find that fitting a ring spanner on the hex part and hitting the other end of it with a rubber mallet while someone else hangs on to the tap works ok.

Roger Mills presented the following explanation :

When you do get the cartridge out, leave it to soak in lemon juice or citric acid to remove the limescale. Limescale will be the cause of the drip.

I don't think it's that, but I'll keep an eye on it.

Basically trying that. In the end it might be necessary to remove the tap and put it in a vice. A few months ago we had the plumber in for another job, and I asked him if he could just loosen the cartridge and I'd do the rest. He's well over 6 ft and heavily-built, but even he couldn't shift it. He didn't want to try any harder in case the pipework and/or basin got damaged. In the end it might be necessary to remove the tap and put it in a vice. We have hard/very hard water here, and that wouldn't help if scale has formed in the thread.

Jeff Layman submitted this idea :

Soak in citric acid, add toilet paper/ cotton wool to help keep it where needed.

Guess why I regard a water softener as essential.

I've only had to replace one set of taps in 20 years, my cylinder still works fine as do all the shower heads, and the bogs are squeaky clean

I'm assuming you can't get it out and shove it in an ultrasonic cleaner? Brian

There is a lot to be said for good old taps with old fashioned washers. Brian

Is that why you're soft in the head? :)

Cheap, tacky, juvenile. That's Our Pam.