When replacing the brass mixer tap cartridge, the process is simple and easy. Make sure the seals on the new cartridge are aligned properly. Apply some heat-resistant silicone plumber's grease to the seals of the cartridge. Pull the top of the stem to a slightly higher position to insert the new cartridge. Once it is in, you can now turn on the faucet and start enjoying the clean water again. Just don't forget to apply the grease on the shaft and the O-rings.