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I have been using Mean Green to shampoo my carpets for years. I use about 1/2 cup per gallon of water and it doesn't clog up your pump like pine oil will.
Cleaning Carpet
Make Your Own Cleaning Products
Using Shampoo as a Carpet Stain Remover
Homemade Carpet Cleaner Recipes
Homemade Furniture Polish Recipes
Removing Mildew from Carpet
Using Vinegar and Water in a Carpet Cleaner
Cleaning Smelly Carpet?