Cat wee smell in carpet - HELP!

[kaz35]

Hi, can anyone recommend a good home remedy / dry shampoo for getting rid of the above....The smell is old, I've shampooed the carpet and also used a specific carpet spray for this purpose, but I can still smell stale cat wee, although it is much fainter than it was. Little so-and-so did it right behind my lounge door and I can smell it when the door wafts over it! Any help appreciated!

[vascop]

Buy a new carpet and kill the cat!