The second stage vent is bigger and more obvious. Remember, better safe than sorry. The vent on the first stage is quite tiny, often just a small hole.
Compare with similar items. The vent on the first stage is quite tiny, often just a small hole. I thought it may have been an anomaly, so I waited till the secondary tank went empty, and again, it never automatically switched over. Can I run these pigtails from the tanks to a tee then to the regulator. Please try again later. Quality control is never perfect, if the replacement lasts, I'll update this review to 5 stars in a few months, but for my money, a company that stands by their products is at least as important as the product itself. To use it properly, make sure both propane tanks are turned on, then switch the lever to one tank.