I don't worry about water on short rides like that. As you saw, you didn't need to, either. On long rides, there's a limit of about 1 liter/hour being all you can get to cross the stomach wall. Even that much may require training for some people. As most folks above said, about 1 bottle/hour is normal. However, it's possible to lose a lot more than that. So on a long ride, here's what I do: I drink to thirst. If I don't think I'm as thirsty as I should be, I take one or more Endurolytes, which stimulate thirst and provide electrolytes to match the water.

I have a maxim which is that I should pee about every 3 hours. If after 3 hours I can't pee, I sit in the shade somewhere, drink water and take Endurolytes until I can, then go on. This sometimes takes 20 minutes, but it's better than heat stroke.

A good sign of damaging dehydration is increased heart rate. I've seen my resting HR go up to 130 on a long, hot ride with a lot of climbing. Sit in the shade and drink until it goes back down to 100. My morning resting HR is ~46. Around here, another good sign is having a light sweat on the forearms. Lack of moisture is a bad sign. However I understand that in very low humidity this is not helpful.

Lance once lost 13 lbs. on a hot 50 mile TT IIRC. He was toast then and the next day.