When we stopped at the visitor center we found out the time Old Faithful would erupt. It had just erupted so we had 90 minutes to get there to see the next eruption. We made it with about ten minutes to spare. There was a huge crowd there. I had been to Yellowstone 2 other times- back in the mid 1970’s and 20 years ago. Things around Old Faithful have changes- they have a huge new visitor center there now. There were more people there to watch the eruption than I recall on my other two trips. It was the most crowded place we ran across all day.
Old Faithful erupts on average every 91 minutes. 3700 gallons of water come out with each eruption. At its top height it reaches 106 feet. Duration of the eruption is 1.5 minutes to 5 minutes.