I thought that you might have had more answers by now and my input would not be needed. However, I'm not a big user of conventional pressure cookers but I have used them in the past.

The answer to your question would depend on what you are cooking. Because you dont evaporate water away you don't need to add any more water than you would want to be be there at the end. Because the pressure allows the temperature to be a lot higher than 100%C, normal cooking times are reduced. Some pressure cookers had a perforated platform which allowed you to lift the food to be cooked above the water. So, what are you cooking that gets watery?