Cleaning a carpet is supposed to make it look better -- not create unsightly ripples and bulges. In many cases, however, especially when a carpet is more than a few years old, it does end up looking worse after cleaning. Usually, the ripples, bumps and buckling are not the result of improper cleaning but rather of a problem that already existed with the carpet.
Moisture in a carpet can cause fibers in both the carpet itself and its backing to swell. This temporarily creates a loose appearance in the carpet and some ripples, bumps or buckling. This condition is more common in carpets that have been in place for some time and are in need of re-stretching prior to the cleaning. The swelling from the moisture makes the problem more apparent.
Too Much Moisture
If too much water is used in the cleaning process, it can penetrate all the way through the carpet backing, saturating the entire carpet. This situation can cause the backing to separate from the carpet fibers and result in buckling or rippling. In cases of backing separation, the damage will be permanent. Too much water can also cause the carpet to stretch out slightly.
Depending on the type of carpet and its backing, part of the fibers or the backing may dry quicker than other parts. This results in an unusual pull or strain on the carpet that causes it to have small ripples or bumps since the dry areas shrink while the wet areas remain swollen.
If the carpet was not installed properly and installation did not include a complete power stretching, any small amount of moisture can cause rippling or buckling because excess slack that already existed in the carpet will be exacerbated by swelling from the moisture. Carpet should be power stretched upon installation. If no such stretching was performed, it should be done after the carpet has dried.
With the exception of the backing separating from the carpet, ripples and buckling after cleaning are not permanent. Avoid walking on the affected areas until the carpet is completely dry. Drying usually takes about 48 hours, depending on the temperature and humidity in a home. In most cases the carpet will return to its original shape, and the ripples will disappear. If they remain, the carpet should be re-stretched to remove the bumps and ripples.