Cleaning dirty old carpet is a challenge because once dirt and sand reach the bottom of the carpet, it's almost impossible to get it out. You can clean carpets yourself with a rented carpet cleaner. These machines use two methods for cleaning: hot water extraction or an agitator brush. Preferably your machine has both.

No matter how clean you keep your home, old carpets accumulate stains and appear dingy. Regular cleaning brightens the carpet and removes the stains. While many carpet cleaning solutions and stain removers contain harsh chemicals and emit strong odors, a few common household products can clean your carpets effectively. You can make homemade cleaners odorless if you have sensitivities to strong scents or add some natural scents for an extra clean smell. As an additional benefit, you can save money by making your own homemade carpet cleaners.

Step 1:

Sweep your carpet with a broom to lift the fibers and remove loose dirt. Vacuum the entire carpet. (See References 2)
Step 2:

Mix one part borax with two parts cornmeal to make a carpet powder that removes stains, prevents mold growth and deodorizes. Alternately, for carpets with heavy odors, use baking soda. (See References 1 and 2)
Step 3:

Sprinkle the mixture over the entire carpet. Wait for about an hour and then vacuum the carpet. This should remove odor, light stains and dirt that normal vacuuming misses. (See References 1 and 2)
Step 4:

Pre-treat any remaining stains with a mixture of equal parts vinegar and water. For tough stains on light colored carpets, try a mixture of lemon juice and salt. First test any stain-removing mix, especially on darker carpets, in a hidden location, such as a closet. (See References 1)
Step 5:

Scrub the stain with the stain-removing mixture and allow it to sit for 15 minutes. Use an old towel to dab up as much of the moisture as possible.
Step 6:

Rent a carpet-cleaning machine if you do not have one. Use very hot water to remove dirt and stains more effectively.
Step 7:

Fill the soap reservoir with a natural carpet cleaning solution. If you use your own carpet cleaner and it doesn't void the warranty, you can use a natural laundry detergent in place of carpet cleaner. If you don't want to use any detergent, the hot water alone will remove much of the accumulated grime.
Step 8:

Clean the entire carpet one time with the cleaner following the manufacturer's instructions. Run the carpet cleaner over the carpet once more with just hot water to rinse any detergent residue. Make a third pass without spraying any water or detergent to suck up as much moisture as you can.
Step 9:

Stay off the carpet until it dries completely. Once dry, vacuum the carpet again to fluff the nap and remove the last of any soap residues.

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Author's Bio: 

Graeme Stephens has been running the largest owned carpet cleaning company
in new Zealand for 24 years. IICRC qualified "master restoration technician"