Any way you clean your carpets, fact is that a residue get left behind.
You may precondition your carpet with expensive products, use alkaline rinses or even acids and water rinses, no matter what...
you will end up with some residue.
But these too can be taken care of.
The common kinds of residues are alkaline, acid, neutral, water and compound based residue.
A common carpet cleaning problem is when cleaners use detergents.
These tend to foam up during the process.
What you need to do then is turn down the heat or else use a cold water rinse.
This will prevent the detergent from foaming too much.
You get powdered defoamers that can be used directly on the carpet.
Residues are in fact good for carpets.
But you will need to determine which residue best suits your carpet.
While alkaline residues are good, too much of it tends increase the crustiness of the carpet and they get soiled again easily.
Acid residues on the hand give your carpet a soft feeling and keep soils at bay preventing it from getting dirty too soon.
In this cases, always stick to the manufacturer's instructions.
Neutral residues have been getting a lot of attention these days.
They remain neutral on the pH scale.
Water based residues are also popular for their easy availability.
The only issue with this is that water does not contain a pre-conditioner that's necessary to maintain the sheen of the carpet.
If you are using a chemical based residue then, it best to use warm water as a rinse.
This helps in removing a majority of the chemical.
The best way to check which residue work well for you is to attempt to use it on a discreet part of the carpet.
This way, even if it does not agree with your carpet, it will be in a spot that is not really seen.