Although proper maintenance can dramatically extend the life of your carpet, every carpet that sees regular use will need to be replaced sooner or later. Some of the signs can be obvious, but there are others that may be more subtle.

To determine when you should replace your own carpet, consider the following top six signs that reveal irreversible wear and tear:

1. Stains in carpet

Are you covering up carpet stains with furniture and rugs when carpet cleaning fails to remove them? If your house is starting to resemble a minefield, it’s time for a carpet replacement. Most carpets come with a stain-resistant finish, but over time, the treatment fades and eventually leaves the carpet unprotected.

Luckily, professional carpet cleaners know tricks to remove tough stains. Dean Leffel, owner of highly rated Home Cleaning Centers of America in Indianapolis, says most carpet cleaners only clean to the base of your carpet, to avoid damaging the glue that binds your carpet to the pad. However, he says this doesn’t get any stains that penetrate deeper than the carpet.

“We have a system of flushing out deep stains with a flood extraction tool,” he says. In this method, Leffel floods the area with cleaning solution and uses a heavy duty extraction tool to remove the stain from the carpet and pad.

Sometimes, Leffel says, stubborn stains just won’t go away. Bleach, plant food, tea, wine and mustard are typically the toughest stains to remove, and carpet cleaners say many homeowners make the stains worse by using shoddy DIY stain-removal methods they find on the web, or store-bought carpet-cleaning products that can actually damage carpet with harsh chemicals.

Stains caused by pet urine, feces, vomit, mold and mildew are usually easy to clean if you act fast. But these biological substances eventually will absorb into the carpet padding, leading to mold and mildew buildup under the carpet. If the biological stains are in several places, consider replacing the carpet to avoid health hazards with mold. Leffel says they sometimes get creative with replacing small pieces of stained carpet by removing carpet from a rarely used closet.