It's hard to offer advice on alternative products when on the other channel out of respect for their forum but I would look at the stain and see if there is any degregation I have extracted them before and pulled out fibres which weren't quite loose.
What you could do is apply prochem citrus gel massage in then rinse then apply rust remover allow dwell then rinse, this may get rid of brown rust or the black mark left usually around the pipe.
The reason why we give the worst case scenario is that if you come across that scenario you know how to deal with it and also if it all goes pear shaped the 'last person to touch it' comes into affect and you could end up owning an old carpet and a few £s missing from your bank account.
Shaun