You don't have to wash canned pinto beans, but the practice has several benefits. Perhaps most important is reduced sodium content (although some stores sell canned beans with no salt added). Washing canned beans might make them tastier, and it can mitigate bean-induced flatulence.
Reasons for Rinsing
Washing canned pinto beans can remove significant amounts of sodium. Simply draining beans can reduce sodium content by 36 percent, and rinsing can remove another 5 percent.
Canned beans typically contain a mushy residue at the bottom of the can. It's OK to eat this, but it's likely to contain sodium, and removing it may improve the taste.
Rinsing beans removes raffinose, a sugar that causes flatulence. That should be reason enough on its own for washing canned beans.
How to Wash Canned Pinto Beans
It's simple to wash canned pinto beans before use. Pour the beans into a colander and let them drain for two minutes. Rinse for at least 10 seconds with cold water. Let the beans drain in the colander for two more minutes. That's all there is to it.