I had a leaky Moen faucet (Moen 4600) so I removed the old cartridge and replaced it with a new brass replacement cartridge (model 1200.) Since replacing the cartridge I now have a leak from the valve stem, that leaks faster the more I open the valve. It appears to be coming from the outside collar of the cartridge. Here is a video of the leak so you can see exactly what I am talking about:
Is this caused by a poor fitting cartridge / o-ring or is it possibly due to wear on the faucet itself? What can I do to stop this leak?