Following a painting project, it's important to dispose of excess paint properly. Depending on local laws and regulations, you may not be able to simply throw paint in the trash. Instead, there are certain methods for disposal that are both safe for the environment and, in many cases, required by law.
Paint Disposal Basics
While most paint isn't considered a hazardous material, it can't be disposed of unless the paint has completely dried out. There are several methods to dry out cans of latex paint, depending on how much time you have. The National Paint and Coatings Association states that paint comprises the largest volume of waste collected by hazardous waste programs throughout the country. When you can't use up or donate leftover paint, you may be able to dry it out in the can and dispose of it with your regular trash if your waste collection company permits.
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How to Dry Out Paint
To dry out your paint, leave the can open in a warm, dry place. If there's 1 inch or less of paint in the can, it will dry out within a few days.
Adding absorbent materials, such as sawdust or cat litter, to the paint can help it to dry out more quickly. Stir it frequently to encourage drying. You can also attempt to dry out your paint by pouring it into many small containers so it dries more quickly.
Commercial paint hardener is available for purchase at local hardware stores and home improvement chains. Paint hardener is manufactured as an absorbent powder. If you mix this powder in with your leftover paint as directed per package instructions, it should dry up large amounts of paint within a couple of days.
Once your paint has dried, you can put it in the trash. You should leave the lids off your paint cans when doing so, however, so that trash collectors don't reject it because they think it's full.
Abide by Local Laws
Before moving forward with any disposal methods, call your local government to see if they have a donation program for unwanted paint. If you have quite a bit of paint, it's better to donate it than to throw it away. If your area doesn't accept donations of these kinds, you may be able to include your leftover paint in a hazardous waste collection day.
Take note of different regulations depending on the type of paint you're throwing away. In some jurisdictions, you may be allowed to throw out water-based or latex paints that aren't dried. Most areas won't permit the disposal of oil-based paints this way, however.
Don't flush excess paint down the toilet or a sink. Doing so is very damaging to your water supply and plumbing. In addition, it's illegal in some areas and can be very harmful to plants and animals further along in the ecosystem, as well.