The new golden rule to remember with plastic bottles: "Empty and replace cap."
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If you're a diligent recycler who always separates your plastics, paper, and glass, you're probably well-versed in having to clean out containers, remove labels, and wash some materials as well. But one rule you've probably been following isn't necessary–or even helpful to the environment.

For years, recyclers were told to remove bottle caps from plastic water bottles and flatten the bottles before putting them in the recycling bin so they wouldn't cause jams in processing machines. It turns out that neither of those steps is necessary anymore and may actually be doing more harm than good.

"...When recycling gets easier, participation goes up," the Association of Plastic Recyclers (APR) says. "The cap material is recyclable. Why dispose of something that could be recycled?"

In the past, the plastics recycling industry was not able to recycle bottles with caps still on. During that time, messaging went out that people should remove the caps to ensure the bottle got recycled. However, recycling collection and processing technology has vastly improved over the years, so you no longer have to take the extra step.

Caps are typically made from "high-density polyethylene (HDPE) and polypropylene (PP)," which are in high demand for recycling in domestic and export markets. So recycling the caps could actually do your local recycling plant a big favor. Recycling plant PetStar produced a video breaking down how the machinery processes PET bottles with caps, which is the kind of food-grade plastic most of us are using and recycling often.

Additionally, the APR is changing its tune on flattening bottles. It noted that when a bottle is flattened, it can accidentally be sorted into the paper stream instead.

"APR's primary message is EMPTY AND REPLACE CAP," the group said. "According to a recent MRF Material Flow Study, flattening bottles can lead to improper sortation, and they may end up in the paper stream. Retaining a 3D form can help containers be successfully sorted."

Floris van Hest, director of the Dutch environmental group North Sea Foundation, points out that because plastic caps do not get recycled properly, they "are among the top five most commonly found items of litter on beaches worldwide."

Based on the organization's 2016 analysis of the Dutch North Shore coastline, 80 percent of bottle caps found littering the shore were from consumer drinks and food packaging, and 70 percent of the bottle caps were damaged. The deterioration suggests the bottle caps had been floating around in the ocean for a while before being disposed of on the shore. According to the research, plastic bottle caps not only disintegrate very slowly, but they're also among the top-five deadliest ocean pollutants for sea life.

Ideally, you're using reusable water bottles and metal straws. But the best way to recycle a plastic bottle is to rinse it out, replace the cap, and put it in the bin. Contact your local recycling facility to ensure they have the right equipment to process the caps and bottles. If they don't, ask for their preferred method of sorting and follow that instead.